Innovative perspectives on the value of diagnostic tests in clinical practice / Perspectivas innovadoras sobre el valor de las pruebas diagnósticas en la práctica clínica

Abstract Diagnostic tests have intrinsic characteristics such as sensitivity, specificity, overall accuracy and likelihood ratios which define their operational performance. It is not uncommon to find in the literature that test value and clinical utility are defined based exclusively on those characteristics. This paper introduces several arguments aimed at prompting a reflection regarding the characteristics that define the true value of diagnostic tests in clinical practice. It concludes with the view that the value of each diagnostic test needs to be established in accordance with the circumstances in which it is used, taking into account extrinsic characteristics such as in whom it is used, when, where and by who.

Resumen Las pruebas diagnósticas tienen características intrínsecas, como la sensibilidad, especificidad, exactitud global y las razones de verosimilitud, que definen su desempeño operacional. No es infrecuente encontrar en la literatura que se valore la prueba y se defina su utilidad clínica exclusivamente de acuerdo con estas características. En este documento se presentan varios argumentos que permiten reflexionar sobre las características que verdaderamente definen el valor de las pruebas diagnósticas en la práctica clínica. Se concluye con una perspectiva en la que el valor de cada prueba diagnóstica se establece de acuerdo con las circunstancias de uso de la misma: de quién, cuándo, dónde y en quién se use la prueba, y todas estas son características extrínsecas de una prueba diagnóstica.

Comparison of the sensitivity and specificity of commercial anti-dengue virus IgG tests to identify persons eligible for dengue vaccination.

The Advisory Committee on Immunization Practices (ACIP) recommended that dengue pre-vaccination screening tests for Dengvaxia administration have at least 98% specificity and 75% sensitivity. This study evaluates the performance of commercial anti-DENV IgG tests to identify tests that could be used for pre-vaccination screening. First, for seven tests, we evaluated sensitivity and specificity in early convalescent dengue virus (DENV) infection, using 44 samples collected 7-30 days after symptom onset and confirmed by RT-PCR. Next, for the five best-performing tests and two additional tests (with and without an external test reader) that became available later, we evaluated performance to detect past dengue infection among a panel of 44 specimens collected in 2018-2019 from healthy 9- to 16-year-old children from Puerto Rico. Finally, a full-scale evaluation was done with the four best-performing tests using 400 specimens from the same population. We used virus focus reduction neutralization test and an in-house DENV IgG ELISA as reference standards. Of seven tests, five showed ≥75% sensitivity in detecting anti-DENV IgG in early convalescent specimens with low cross-reactivity to the Zika virus. For the detection of previous DENV infections, the tests with the highest performance were the Euroimmun NS1 IgG ELISA (sensitivity 84.5%, specificity 97.1%) and CTK Dengue IgG rapid test R0065C with the test reader (sensitivity 76.2% specificity 98.1%). There are IgG tests available that can be used to accurately classify individuals with previous DENV infection as eligible for dengue vaccination to support safe vaccine implementation. IMPORTANCE: The Advisory Committee on Immunization Practices (ACIP) has set forth recommendations that dengue pre-vaccination screening tests must exhibit at least 98% specificity and 75% sensitivity. Our research rigorously assesses the performance of various commercial tests against these benchmarks using well-characterized specimens from Puerto Rico. The findings from our study are particularly relevant given FDA approval and ACIP recommendation of Sanofi Pasteur's Dengvaxia vaccine, highlighting the need for accurate pre-vaccination screening tools.

Evaluation of concordance of new QuantiFERON-TB Gold Plus platforms for Mycobacterium tuberculosis infection diagnosis in a prospective cohort of household contacts.

Interferon-gamma (IFN-γ) release assays play a pivotal role in tuberculosis infection (TBI) diagnosis, with QuantiFERON-TB Gold Plus-an enzyme-linked immunosorbent assay (ELISA)-among the most widely utilized. Newer QuantiFERON-TB platforms with shorter turnaround times were recently released. We aimed to evaluate these platforms' agreement in the diagnosis of TBI. Blood samples from a prospective cohort of tuberculosis household contacts were collected at baseline and after 12 weeks of follow-up, and tested with LIAISON, an automated chemiluminescence immunoassay (CLIA) system, QIAreach, a lateral flow (QFT-LF) semi-automated immunoassay, and the ELISA QuantiFERON-TB Gold Plus platform. Test concordances were analyzed. ELISA vs CLIA overall agreement was 83.3% for all tested samples (120/144) [Cohen's kappa coefficient (κ): 0.66 (95% CI: 0.54-0.77)]. Samples positive with CLIA provided consistently higher IFN-γ levels than with ELISA (P < 0.001). Twenty-four (16.7%) discordant pairs were obtained, all CLIA-positive/ELISA-negative: 15 (62.5%) had CLIA IFN-γ levels within borderline values (0.35-0.99 IU/mL) and 9 (37.5%) >0.99 IU/mL. QFT-LF showed only 76.4% (68/89) overall agreement with ELISA [κ: 0.53 (95% CI: 0.37-0.68)] with 21 (23.6%) discordant results obtained, all QFT-LF-positive/ELISA-negative. Overall concordance between ELISA and CLIA platforms was substantial, and only moderate between ELISA and QFT-LF. The CLIA platform yielded higher IFN-γ levels than ELISA, leading to an almost 17% higher positivity rate. The techniques do not seem interchangeable, and validation against other gold standards, such as microbiologically-confirmed tuberculosis disease, is required to determine whether these cases represent true new infections or whether CLIA necessitates a higher cutoff. IMPORTANCE: Tuberculosis is an airborne infectious disease caused by Mycobacterium tuberculosis that affects over 10 million people annually, with over 2 billion people carrying an asymptomatic tuberculosis infection (TBI) worldwide. Currently, TBI diagnosis includes tuberculin skin test and the blood-based interferon-gamma (IFN-γ) release assays, with Qiagen QuantiFERON-TB Gold Plus (QFT) being among those most widely utilized. We evaluated Qiagen's newer QFT platforms commercially available in a prospective cohort of tuberculosis contacts. A substantial agreement was obtained between the current QFT-enzyme-linked immunosorbent assay (ELISA) and the new QFT-chemiluminescence immunoassay (CLIA) platform, although QFT-CLIA provided higher concentrations of IFN-γ, leading to a 16.6% higher positivity rate. We highlight that both platforms may not be directly interchangeable and that further validation is required.

Diagnostic Methods for Helicobacter pylori.

Helicobacter pylori infection is a significant global health concern. It cannot be diagnosed based solely on the patient's medical history and symptoms, and laboratory and imaging tests are often required to confirm the diagnosis. Both noninvasive and invasive methods are available for diagnosing H. pylori infection, including conventional and advanced detection techniques. It is not uncommon for patients to present with false-negative results due to the use of inadequate investigation methodologies, which prevents the adoption of appropriate clinical management. Thus, an analysis of the literature regarding the methods of diagnosis of H. pylori, with its advantages and disadvantages, is necessary. Publications in specialized scientific journals will undoubtedly contribute to facilitating access by professionals interested in the topic providing greater knowledge and potentially clinically useful guidance. In this review, the authors have sought to analyze and summarize the invasive and noninvasive methods, their applications, limitations, and the conditions that affect the sensitivity of the tests used for diagnosing H. pylori, an essential step for the successful treatment of this infection. It is essential to treat all patients infected with H. pylori. This represents a significant change in the approach, as the treatment was recommended previously only for patients showing symptoms of infection. Therefore, it is crucial to understand the limitations of traditional diagnostic methods and help raise awareness among healthcare professionals about the latest advances in diagnosing this important bacterium.

Urea breath test for Helicobacter pylori infection in adult dyspeptic patients: A meta-analysis of diagnostic test accuracy.

BACKGROUND: Helicobacter pylori (H. pylori) infection has been well-established as a significant risk factor for several gastrointestinal disorders. The urea breath test (UBT) has emerged as a leading non-invasive method for detecting H. pylori. Despite numerous studies confirming its substantial accuracy, the reliability of UBT results is often compromised by inherent limitations. These findings underscore the need for a rigorous statistical synthesis to clarify and reconcile the diagnostic accuracy of the UBT for the diagnosis of H. pylori infection. AIM: To determine and compare the diagnostic accuracy of 13C-UBT and 14C-UBT for H. pylori infection in adult patients with dyspepsia. METHODS: We conducted an independent search of the PubMed/MEDLINE, EMBASE, and Cochrane Central databases until April 2022. Our search included diagnostic accuracy studies that evaluated at least one of the index tests (13C-UBT or 14C-UBT) against a reference standard. We used the QUADAS-2 tool to assess the methodological quality of the studies. We utilized the bivariate random-effects model to calculate sensitivity, specificity, positive and negative test likelihood ratios (LR+ and LR-), as well as the diagnostic odds ratio (DOR), and their 95% confidence intervals. We conducted subgroup analyses based on urea dosing, time after urea administration, and assessment technique. To investigate a possible threshold effect, we conducted Spearman correlation analysis, and we generated summary receiver operating characteristic (SROC) curves to assess heterogeneity. Finally, we visually inspected a funnel plot and used Egger's test to evaluate publication bias. RESULTS: The titles and abstracts of 4621 studies were screened; 79 articles were retrieved and selected for full-text reading. Finally, 60 studies were included in the diagnostic test accuracy meta-analysis. Our analysis demonstrates superior diagnostic accuracy of 13C-UBT over 14C-UBT, indicated by higher sensitivity (96.60% vs 96.15%), specificity (96.93% vs 89.84%), likelihood ratios (LR+ 22.00 vs 10.10; LR- 0.05 vs 0.06), and area under the curve (AUC; 0.979 vs 0.968). Notably, 13C-UBT's DOR (586.47) significantly outperforms 14C-UBT (DOR 226.50), making it the preferred diagnostic tool for dyspeptic individuals with H. pylori infection. Correlation analysis revealed no threshold effect (13C-UBT: r = 0.48; 14C-UBT: r = -0.01), and SROC curves showed consistent accuracy. Both 13C-UBT and 14C-UBT showed high AUC values (13C-UBT 0.979; 14C-UBT 0.968) near 1.00, reinforcing their excellent accuracy and endorsing both as reliable diagnostic tools in clinical practice. CONCLUSION: In summary, our study has demonstrated that 13C-UBT has been found to outperform the 14C-UBT, making it the preferred diagnostic approach. Additionally, our results emphasize the significance of carefully considering urea dosage, assessment timing, and measurement techniques for both tests to enhance diagnostic precision. Nevertheless, it is crucial for researchers and clinicians to evaluate the strengths and limitations of our findings before implementing them in practice.

A cost-effectiveness analysis of a novel algorithm to sequentially diagnose leprosy based on manufactured tests under the SUS perspective / Análise de custo-efetividade de um novo algoritmo para exame sequencial de hanseníase baseado em testes fabricados sob a perspectiva do SUS / Análisis de costo-efectividad de un nuevo algoritmo para el examen secuencial de lepra basado en pruebas fabricadas bajo la perspectiva del SUS

Abstract: Brazil has the second largest number of leprosy cases (a disease with a significant burden) in the world. Despite global and local efforts to eliminate this public health problem, inadequate or late diagnosis contribute to perpetuate its transmission, especially among household contacts. Tests such as the rapid IgM antibody detection (RT) and real-time polymerase chain reaction (RT-PCR) were developed to overcome the challenges of early diagnosis of leprosy. This study aimed to analyze the cost-effectiveness of a new diagnostic algorithm recommended by the Brazilian government to diagnose leprosy in household contacts of confirmed leprosy cases, which includes the RT and RT-PCR tests. A decision tree model was constructed and the perspective of the Brazilian Unified National Health System (SUS) and a 1-year time horizon were adopted. Only direct medical costs related to diagnostic tests were included. Effectiveness was measured as the number of avoided undiagnosed leprosy cases. Different scenarios were analyzed. The sequential use of RT, slit-skin smear (SSS) microscopy, and RT-PCR as recommended by the Brazilian Ministry of Health was compared to a base case (isolated SSS microscopy), yielding an incremental cost-effectiveness ratio of USD 616.46 per avoided undiagnosed leprosy case. Univariate sensitivity analysis showed that the prevalence of leprosy among household contacts was the variable that influenced the model the most. This is the first economic model to analyze a diagnostic algorithm of leprosy. Results may aid managers to define policies and strategies to eradicate leprosy in Brazil.

Resumo: O Brasil tem o segundo maior número de casos de hanseníase (doença com carga significativa) do mundo. Apesar dos esforços globais e locais para eliminar esse problema de saúde pública, o diagnóstico inadequado ou tardio contribui para perpetuar sua transmissão, especialmente entre contatos intradomiciliares. Exames como o teste rápido de anticorpos IgM (RT) e a reação em cadeia da polimerase em tempo real (RT-PCR) foram desenvolvidos para superar as barreiras do diagnóstico precoce da hanseníase. Este estudo teve como objetivo analisar a relação custo-efetividade de um novo algoritmo de diagnóstico recomendado pelo governo brasileiro para diagnosticar a hanseníase em contatos domiciliares de casos confirmados de hanseníase, que inclui os testes RT e RT-PCR. Foi construído um modelo de árvore de decisão e adotada a perspectiva do Sistema Único de Saúde (SUS) considerando o período de um ano. Foram incluídos apenas os custos médicos diretos relacionados aos exames diagnósticos. A efetividade foi medida considerando o número de casos evitados de hanseníase. Diferentes cenários foram analisados. O uso sequencial de RT, baciloscopia e RT-PCR, conforme recomendado pelo Ministério da Saúde, foi comparado a um caso base (baciloscopia isolada), obtendo-se uma razão de custo-efetividade incremental de USD 616,46 por caso evitado de hanseníase. A análise de sensibilidade univariada mostrou que a prevalência de hanseníase entre contatos intradomiciliares foi a variável que mais influenciou o modelo. Este é o primeiro modelo econômico a analisar um algoritmo diagnóstico da hanseníase. Os resultados poderão auxiliar os gestores na definição de políticas e estratégias para a erradicação da hanseníase no Brasil.

Resumen: Brasil tiene el segundo mayor número de casos de lepra (enfermedad con carga significativa) del mundo. A pesar de los esfuerzos globales y locales para eliminar ese problema de salud pública, el diagnóstico inadecuado o tardío contribuye a perpetuar su transmisión, sobre todo entre contactos intradomiciliarios. Los exámenes como la prueba rápida de anticuerpos IgM (RT) y la reacción en cadena de la polimerasa en tiempo real (RT-PCR) se desarrollaron para superar las barreras del diagnóstico precoz de la lepra. El objetivo de este estudio fue analizar la relación de costo-efectividad de un nuevo algoritmo de diagnóstico recomendado por el gobierno brasileño para diagnosticar la lepra en contactos domiciliarios de casos confirmados de lepra, que incluye las pruebas RT y RT-PCR. Se construyó un modelo de árbol de decisión y se adoptó la perspectiva del Sistema Único de Salud (SUS) teniendo en cuenta el periodo de un año. Solo se incluyeron los costos médicos directos relacionados con los exámenes diagnósticos. Se midió la efectividad teniendo en cuenta el número de casos de lepra evitados. Se analizaron distintos escenarios. Se comparó el uso secuencial de RT, baciloscopia y RT-PCR, conforme el Ministerio de Salud recomienda, con un caso base (baciloscopia aislada), y se obtuvo un cociente de costo-efectividad incremental de USD 616,46 por cada caso de lepra evitado. El análisis de sensibilidad univariante mostró que la prevalencia de lepra entre contactos intradomiciliarios fue la variable que más influyó el modelo. Este es el primer modelo económico que analiza un algoritmo diagnóstico de lepra. Los resultados podrán ayudar los gestores a definir políticas y estrategias para erradicar la lepra en Brasil.

Electrochemical Paper-Based Nanobiosensor for Rapid and Sensitive Detection of Monkeypox Virus.

Monkeypox virus (MPXV) infection was classified as a public health emergency of international concern by the World Health Organization (WHO) in 2022, being transmitted between humans by large respiratory droplets, in contact with skin lesions, fomites, and sexually. Currently, there are no available accessible and simple-to-use diagnostic tests that accurately detect MPXV antigens for decentralized and frequent testing. Here, we report an electrochemical biosensor to detect MPXV antigens in saliva and plasma samples within 15 min using accessible materials. The electrochemical system was manufactured onto a paper substrate engraved by a CO2 laser machine, modified with gold nanostructures (AuNS) and a monoclonal antibody, enabling sensitive detection of A29 viral protein. The diagnostic test is based on the use of electrochemical impedance spectroscopy (EIS) and can be run by a miniaturized potentiostat connected to a smartphone. The impedimetric biosensing method presented excellent analytical parameters, enabling the detection of A29 glycoprotein in the concentration ranging from 1 × 10-14 to 1 × 10-7 g mL-1, with a limit of detection (LOD) of 3.0 × 10-16 g mL-1. Furthermore, it enabled the detection of MPXV antigens in the concentration ranging from 1 × 10-1 to 1 × 104 PFU mL-1, with an LOD of 7.8 × 10-3 PFU mL-1. Importantly, no cross-reactivity was observed when our device was tested in the presence of other poxvirus and nonpoxvirus strains, indicating the adequate selectivity of our nanobiosensor for MPXV detection. Collectively, the nanobiosensor presents high greenness metrics associated with the use of a reproducible and large-scale fabrication method, an accessible and sustainable paper substrate, and a low volume of sample (2.5 µL), which could facilitate frequent testing of MPXV at point-of-care (POC).

Differential levels of anti-Mycobacterium tuberculosis-specific IgAs in saliva of household contacts with latent tuberculosis infection.

Introduction: Mucosal immunity is strongly elicited in early stages of many respiratory and enteric infections; however, its role in tuberculosis pathogenesis has been scarcely explored. We aimed to investigate Mycobacterium tuberculosis (Mtb) specific IgA levels in saliva in different stages of latent Tuberculosis Infection (TBI). Methodology: A multiplex bead-based Luminex immunoassay was developed to detect specific IgA against 12 highly immunogenic Mtb antigens. A prospective cohort of household contacts (>14 years) of pulmonary TB cases was established in Santiago, Chile. Contacts were classified as Mtb-infected or not depending on serial interferon-γ release assay results. Saliva samples were collected and tested at baseline and at a 12-week follow-up. Results: Mtb-specific IgA was detectable at all visits in all participants (n = 168), including the "non-Mtb infected" (n = 64). Significantly higher median levels of IgA were found in the "Mtb infected" compared to the uninfected for anti-lipoarabinomannan (LAM) (110 vs. 84.8 arbitrary units (AU), p < 0.001), anti-PstS1 (117 vs. 83 AU, p < 0.001), anti-Cell Membrane Fraction (CMF) (140 vs. 103 AU, p < 0.001) and anti-Culture Filtrate Proteins (CFP) (median 125 vs. 96 AU, p < 0.001), respectively. Nonetheless, the discriminatory performance of these specific mucosal IgA for TBI diagnosis was low. Conclusion: Saliva holds Mtb-specific IgA against several antigens with increased levels for anti-LAM, anti-PstS1, anti-CMF and anti-CFP found in household contacts with an established TBI. The role of these mucosal antibodies in TB pathogenesis, and their kinetics in different stages of Mtb infection merits further exploring.

Turning chaotic sample group clusterization into organized ones by feature selection: Application on photodiagnosis of Brucella abortus serological test.

Bovine brucellosis diagnosis is a major problem to be solved; the disease has a tremendous economic impact with significant losses in meat and dairy products, besides the fact that it can be transmitted to humans. The sanitary measures instituted in Brazil are based on disease control through diagnosis, animal sacrifice, and vaccination. Although the currently available diagnostic tests show suitable quality parameters, they are time-consuming, and the incidence of false-positive and/or false-negative results is still observed, hindering effective disease control. The development of a low-cost, fast, and accurate brucellosis diagnosis test remains a need for proper sanitary measures at a large-scale analysis. In this context, spectroscopy techniques associated with machine learning tools have shown great potential for use in diagnostic tests. In this study, bovine blood serum was investigated by UV-vis spectroscopy and machine learning algorithms to build a prediction model for Brucella abortus diagnosis. Here we first pre-treated the UV raw data by using Standard Normal Deviate method to remove baseline deviation, then apply principal component analysis - a clustering method - to observe the group formation tendency; the first results showed no clustering tendency with a messy sample score distribution, then we properly select the main principal components to improve clusterization. Finally, by using machine learning algorithms (SVM and KNN), the predicting models achieved a 92.5% overall accuracy. The present methodology provides a test result in an average time of 5 min, while the standard diagnosis, with the screening and confirmatory tests, can take up to 48 h. The present result demonstrates the method's viability for diagnosing bovine brucellosis, which can significantly contribute to disease control programs in Brazil and other countries.

Evaluation of a rapid diagnostic test for measles IgM detection; accuracy and the reliability of visual reading using sera from the measles surveillance programme in Brazil, 2015.

Laboratory-based case confirmation is an integral part of measles surveillance programmes; however, logistical constraints can delay response. Use of RDTs during initial patient contact could enhance surveillance by real-time case confirmation and accelerating public health response. Here, we evaluate performance of a novel measles IgM RDT and assess accuracy of visual interpretation using a representative collection of 125 sera from the Brazilian measles surveillance programme. RDT results were interpreted visually by a panel of six independent observers, the consensus of three observers and by relative reflectance measurements using an ESEQuant Reader. Compared to the Siemens anti-measles IgM EIA, sensitivity and specificity of the RDT were 94.9% (74/78, 87.4-98.6%) and 95.7% (45/47, 85.5-99.5%) for consensus visual results, and 93.6% (73/78, 85.7-97.9%) and 95.7% (45/47, 85.5-99.5%), for ESEQuant measurement, respectively. Observer agreement, determined by comparison between individuals and visual consensus results, and between individuals and ESEQuant measurements, achieved average kappa scores of 0.97 and 0.93 respectively. The RDT has the sensitivity and specificity required of a field-based test for measles diagnosis, and high kappa scores indicate this can be accomplished accurately by visual interpretation alone. Detailed studies are needed to establish its role within the global measles control programme.

Rapid Detection of SARS-CoV-2 Based on the LAMP Assay Associated with the CRISPRCas12a System.

BACKGROUND: The global public health system has been severely tested by the COVID-19 pandemic. Mass testing was essential in controlling the transmission of the SARS-CoV-2; however, its implementation has encountered challenges, particularly in low-income countries. The urgent need for rapid and accurate tests for SARS-CoV-2 has proven to be extremely important. Point-of-care tests using the CRISPR system for COVID-19 have shown promise, with a reported high sensitivity and rapid detection. The performance of a CRISPR-based SARS-CoV-2 testing system was reported in this study. METHODS: A total of 29 nasopharyngeal samples were evaluated, including 23 samples from individuals suspected of COVID-19, and six samples positive for H3N2 or respiratory syncytial virus. Two reference samples with known concentrations of SARS-CoV-2 RNA (3000 RNA copies/mL) or viral titer determined by plaque assay (105 PFU/mL) were also evaluated. The LAMP technique was employed to amplify the ORF1ab gene and the results were analyzed using a Gemini XPS fluorescence reader. RESULTS: The RT-LAMP-CRISPR/Cas12 assay showed 100% concordance compared to RT-PCR. The RT-PCR presented a detection limit of 0.01 PFU/mL and the CRISPR/Cas12 system showed a limit of 15.6 PFU/mL. The RT-PCR sensitivity was approximately 8 RNA copies/µL and CRISPR/Cas12 at 84 RNA copies/µL. CONCLUSION: The RT-LAMP-CRISPR/Cas12a assay offered a promising alternative for the detection of SARS-CoV-2 and reinforces that CRISPR-based diagnostic techniques can be an alternative for fast and accurate assays.

Diagnostic accuracy of severity measures of ICD-11 and DSM-5 personality disorder: clarifying the clinical landscape with the most up-to-date evidence.

With the implementation of new dimensional models of personality disorder (PD) in the DSM-5 and ICD-11, several investigators have developed and evaluated the psychometric properties of measures of severity. The diagnostic accuracy of these measures, an important cross-cultural metric that falls between validity and clinical utility, remains unclear. This study aimed to analyze and synthesize the diagnostic performance of the measures designed for both models. For this purpose, searches were carried out using three databases: Scopus, PubMed, and Web of Science. Studies that presented sensitivity and specificity parameters for cut-off points were selected. There were no restrictions on the age and gender of the participants nor on the reference standard used or the settings. Study quality and synthesis were assessed using QUADAS-2 and MetaDTA software, respectively. Twelve studies were eligible covering self-reported and clinician-rated measures based on the ICD-11 and DSM-5 PD severity models. A total of 66.7% of the studies showed a risk of bias in more than 2 domains. The 10th and 12th studies provided additional metrics, resulting in a total of 21 studies for evidence synthesis. Adequate overall sensitivity and specificity (Se = 0.84, Sp = 0.69) of these measures were obtained; however, the cross-cultural performance of specific cut-off points could not be assessed due to the paucity of studies on the same measure. Evidence suggests that patient selection processes should mainly be improved (avoid case-control design), use adequate reference standards, and avoid only reporting metrics for the optimal cut-off point.

Development and validation of a flow cytometry antibody test for Lawsonia intracellularis.

Lawsonia intracellularis is the etiologic agent of porcine proliferative enteropathy (PPE), an inflammatory bowel disease with a major economic impact on the pig industry. The serological diagnosis of PPE can be performed using Blocking or Indirect ELISA, Immunoperoxidase Monolayer Assay (IPMA) and Indirect Fluorescence Antibody Test (IFAT). Here, we designed a most sophisticated immunological method for the detection of porcine anti-L. intracellularis IgGs, named Flow Cytometry Antibody Test - FCAT. This assay uses whole, live-attenuated L. intracellularis bacteria derived from a commercial vaccine. For the assay, we set up the optimal antigen concentration (106 bacterium/assay), primary antibody dilution (1:100), time of incubation (20 min), antigen stability (15 days), precision (coefficient of variation - CV < 10%), reproducibility (CV ≤ 13%) and Receiver Operating Characteristic (ROC). When using a cut-off of >15.15% for FCAT, we determined that it showed a sensitivity of 98.8% and specificity of 100%. The rate of agreement with IPMA was 84.09% with a kappa index of 0.66. FCAT was used to screen 1,000 sera from non-vaccinated pigs housed in 22 different farms and we found that 730 pigs (73%) from 16 farms (72.7%) had L. intracellularis IgG. This high prevalence confirms that L. intracellularis is endemic on Brazilian pig farms. Finally, we determined that FCAT is an easy to perform diagnostic assay and we would highly recommend it for: i) seroepidemiological studies; ii) evaluation of infection dynamics; and iii) characterization of the humoral response profile induced by vaccines.

Comparison of Two Tuberculosis Infection Tests in a South American Tertiary Hospital: STANDARD F TB-Feron FIA vs. QIAreachTM QuantiFERON-TB.

INTRODUCTION: Tuberculosis (TB) is one of the most prevalent respiratory diseases in the world. In 2020 there were at least 9.9 million new infections, with 1.5 million deaths. Approximately 10% of people infected with Mycobacterium tuberculosis develop the disease during the first 2 to 5 years after infection. In South America, the diagnosis of Latent Tuberculosis Infections (LTBI) continues to be performed through the Mantoux tuberculin skin test (TST). OBJECTIVE: The objective of our study was to compare the sensitivity of a new immunofluorescence IGRA test against a widely available IGRA kit on the market. MATERIAL AND METHOD: Close contact with infectious TB patients, HIV patients, or immunocompromised for another cause were recruited. Two interferon-gamma release assay (IGRA) diagnostic kits were used and compared with TST. RESULTS: 76 patients were recruited, 93.42% were Chilean nationality, and 98.68% of the patients did not have immunosuppression. The sensitivity of the new technique was 88.89%, and the specificity was 92.50% in the study population compared to the IGRA previously used. In the subgroup older than 36 years, the sensitivity was 95.65%, and the specificity was 89.47%. CONCLUSION: IGRA techniques are a new resource in clinical laboratories to make an accurate diagnosis of LTBI in the region of the Americas. In our population, the greatest benefit of this new IGRA would be observed in people over 36 years of age, where the sensitivity of the technique was like that of the currently available test.

Evaluation of the acceptability of point of care diagnostic test for prenatal toxoplasmosis (translational research phase III).

BACKGROUND: A new point of care test (POC) was developed that is promising as a tool to enhance impact of prenatal care programs for toxoplasmosis, however, no reports exist about its use or acceptability for healthcare personnel and mothers in Colombia. METHODS: This was a translational research - phase III study of the acceptability of a new POC test (Toxoplasma ICT IgG-IgM, LDBio) for qualitative diagnosis of toxoplasmosis in 783 pregnant women and 30 health personnel in primary health care sites in the city of Armenia, Quindío (Colombia). Along with collection of the results of diagnostic POC and confirmatory test and demographic information, we evaluated acceptability through measure of the willingness, credibility, and satisfaction by using questionnaires with a Likert scale during routine prenatal care visits. RESULTS: POC positivity was 46.5% among pregnant participants and was significantly related to socioeconomic factors, including education level (p = 0.00000000) and insurance status (p = 0.00000015). A total of 93-97% of healthcare personnel indicated agreement to positive statements regarding total satisfaction and total credibility of the LDBio test, but qualitative questions identified "Difficulty in the test procedure" as the most common response about barriers to apply the test. Greater than 90% of pregnant participants agree that POC test should be routine for all pregnant woman and permanently implemented. CONCLUSIONS: The test had near complete acceptability. In future studies it is necessary to examine the effect of non-differentiation between IgG and IgM isotypes.

Índice videoquimográfico da função glótica: análise da precisão diagnóstica / Videokymographic index of glottic function: an analysis of diagnostic accuracy

RESUMO Objetivo Elaborar um indicador composto denominado Índice Videoquimográfico da Função Glótica - IVFG, a partir de parâmetros da videoquimografia digital, captados pelo exame de videolaringoscopia de alta velocidade de mulheres sem e com alterações laríngeas de etiologia comportamental. Método A amostra foi composta por 92 mulheres, destas 55 apresentaram disfonia comportamental, com presença de alterações laríngeas e vocais, e 37 mulheres sem alterações laríngeas e vocais, entre 18 a 45 anos. A avaliação vocal foi realizada por consenso pela análise perceptivo-auditiva da vogal /a/ em frequência e intensidade habituais, e classificação através do grau geral da disfonia, onde G0 indicou qualidade vocal neutra e G1 a 3 qualidade vocal alterada. As imagens laríngeas foram obtidas pela gravação da emissão da vogal /i/, em frequência e intensidade habituais para análise da videoquimografia digital. A construção do IVFG se deu pela escolha do ponto médio da glote para análise e, elaboração foi realizada regressão logística pelo programa MINITAB 19. Resultados A regressão logística contou com duas etapas, sendo que a etapa 1 constou da análise de todas as variáveis, onde as variáveis abertura máxima e fechamento glótico apresentaram significância estatística (p-valor <0.05) e o modelo se encontrou bem ajustado de acordo com o teste de Hosmer-Lemeshow (p-valor=0,794); na etapa 2, as variáveis selecionadas foram novamente analisadas e o modelo também se mostrou bem ajustado (p-valor=0,198). O IVFG foi definido por IVFG=e^(8,1318-0,2941AbMax-0,0703FechGlo)/1+e^(8,1318-0,2941AbMax-0,0703FechGlo). Conclusão O IVFG apresenta valor de corte igual a 0,71. A probabilidade de acerto é de 81,5%, sensibilidade 76,4%, especificidade de 89,2%.

ABSTRACT Purpose To develop the Videokymographic Index of Glottic Function (VIGF), a composite indicator from digital videokymography parameters, captured by high-speed videolaryngoscopy exams of women with and without laryngeal alterations of behavioral etiology. Methods The sample consisted of 92 women aged between 18 and 45 years. Fifty-five (55) women with behavioral dysphonia, presenting with laryngeal and voice alterations, and thirty-seven (37) women without any laryngeal and voice alterations. Voice evaluation was performed by consensus via an auditory-perceptual analysis of the sustained vowel /a/ at a habitual pitch and loudness. Voice classification was obtained by means of a general degree of dysphonia, where G0 indicated neutral voice quality and G1 to G3 indicated altered voice quality. Laryngeal images were captured via digital videokymography analysis of a sustained vowel /i/ at a habitual pitch and loudness. The VIGF was based on the midpoint of the glottal region for analysis. Logistic regression was performed using the MINITAB 19 program. Results Logistic regression was composed of two stages: Stage 1 consisted of the analysis of all variables, where the maximum opening and closed quotient variables showed statistical significance (p-value <0.05) and the model was well adjusted according to the Hosmer-Lemeshow test (p-value=0.794). Stage 2 consisted of the re-analysis of the selected variables, also showing a well-adjusted model (p-value=0.198). The VIGF was defined as follows: VIGF=e^(8.1318-0.2941AbMax-0.0703FechGlo)/1+e^(8.1318-0.2941AbMax-0.0703FechGlo). Conclusion The VIGF demonstrated a cut-off value equal to 0.71. The probability of success was 81.5%, sensitivity 76.4%, and specificity 89.2%.

Impacto de la pandemia covid-19 en cirugia de abdomen / Impact of the covid-19 pandemic on abdominal surgery

La rápida propagación de COVID-19 ha hecho que exista una reorganización radical de los recursos sanitarios. Con el objetivo de ver el Impacto de la pandemia COVID-19 en cirugía de abdomen en el IGBJ-La Paz y COSSMIL. Se realizó un estudio descriptivo, retrospectivo y transversal entre marzo a octubre de 2019 previo a la pandemia y marzo a octubre de 2020 durante el periodo de la pandemia. El estudio reunió 836 pacientes, 563 (67.34%) en el grupo de pre-pandemia y 273 (32.66%) en el periodo pandémico, los procedimientos quirúrgicos disminuyeron de 2.3 a 1.2 con p=0,000, las cirugías vesiculares disminuyeron de 51.5% vs 45.4%, cirugía apendicular de 84(14.9%) a 68(24.9%). Los procedimientos electivos disminuyeron de 331 a 79 (80.7% vs 19.3%) p=0.000. Los procedimientos laparoscópicos disminuyeron de 305 (70.4%) a 107 (26.0%) con una p=0.000. Durante la pandemia se estudió 273, de los cuales 7 COVID-19 positivos, el método diagnóstico para COVID-19 más utilizado fue la TC de tórax y ELISA para COVID-19, factor de riesgo más frecuente fue hipertensión arterial 11(4.1%), el tiempo quirúrgico en pacientes COVID-19 positivos /negativos fue de 137 min (+ 30 min), días postoperatorio de 5.6 días en pacientes no COVID-19 y 2.8 días en pacientes COVID+, este último grupo presento 2 complicaciones, 1 absceso de pared de difícil resolución y 1 fallecido. El impacto de la pandemia fue reflejado en una reducción de los procedimientos de cirugía abdominal, en especial en cirugías electivas y laparoscópicos. Durante la pandemia la prueba diagnóstica para COVID-19 más utilizada fue TC de tórax y ELISA, los COVID-19 positivos no tuvieron morbilidad asociada, no se encontró diferencias estadísticas en el tiempo quirúrgico, ni en la estadía postoperatoria entre los pacientes COVID-19 positivos/negativos; los pacientes COVID-19+ presentaron complicaciones.

The rapid spread of COVID-19 has led to a radical reorganization of health resources. This study aimed to analyze the impact of the COVID-19 pandemic on abdominal surgery at IGBJ-La Paz and COSSMIL hospitals. A descriptive, retrospective and cross-sectional study was carried out between March to October 2019 prior to the pandemic, and March to October 2020 during the pandemic period. The study enrolled 836 patients, 563 (67.34%) in the pre-pandemic group and 273 (32.66%) in the pandemic period. Surgical procedures decreased from 2.3 to 1.2 (p=0,000), gallbladder surgeries decreased from 51.5% to 45.4%, appendiceal surgery from 84 (14.9%) to 68(24.9%). Elective procedures decreased from 331(80.7%) to 79 (19.3%), p=0.000. Laparoscopic procedures decreased from 305 (70.4%) to 107 (26.0%), p=0.000. During the pandemic, 273 patients were enrolled, of which 7 were COVID-19 positive, the most used diagnostic method for COVID-19 was chest CT and ELISA test, the most frequent risk factor was arterial hypertension 11 (4.1% ), surgical time in COVID-19 positive/negative patients was 137 min (± 30 min), postoperative days of 5.6 days in non-COVID-19 patients and 2.8 days in COVID+ patients, the latter group had complications, one patient presented wall abscess of difficult resolution, and one patient passed away. The pandemic impact was reflected in a reduction in abdominal surgery procedures, especially in elective and laparoscopic surgeries. During the pandemic, the most used diagnostic test for cOviD-19 were chest CT and ELISA test, positive COVID-19 patients had no associated morbidity, no statistical differences were found in surgical time and postoperative hospital stay days between positive/negative COVID19 patients. COVID-19+ patients presented complications.

Fluorescence-Linked Aptamer Assay for SARS-CoV-2 Spike-Protein: A Step-by-Step Performance Analysis in Clinical Samples.

The COVID-19 pandemic has been a main concern over the last two years and has become one of the most important crises in the history of human health. Today, there is still a need for affordable and reliable diagnostic tests for massive disease monitoring. Previously, a set of highly specific DNA-aptamers (C7/C9) binding to the SARS-CoV-2 Spike (S) protein were isolated but its performance in clinical samples remained to be tested. Here, 242 samples were collected through three different methods and subjected to florescence-linked aptamer assays (FLAA) based on C7/C9 aptamers through two readout protocols. Then, a step-by-step statistical approach which included agreement tests, proportion comparisons and binomial and multinomial logistic regressions was used to predict optimal conditions for the novel C7/C9 FLAA test. RTqPCR threshold cycles, symptoms onset and processing time were influential factors on FLAA test results. Naturally occurring mutations on S were also detected and analyzed. Aminoacidic substitutions D614G and T732A appeared relevant for aptamer recognition although further studies are necessary. The methodology presented here is the first step to determine the performance and diagnosis across a range of clinical contexts and it might serve as a base for a complete analysis applicable to other designs of new diagnostic tests.

Malaria surveillance and case management in remote and indigenous communities of Panama: results from a community-based health worker pilot.

BACKGROUND: Panama is one of eight countries in Mesoamerica that aims to eliminate malaria by 2022. Malaria is concentrated in indigenous and remote regions like Guna Yala, a politically autonomous region where access to health services is limited and cases are predominately detected through intermittent active surveillance. To improve routine access to care, a joint effort was made by Guna Yala authorities and the Ministry of Health to pilot a network of community health workers (CHWs) equipped with rapid diagnostic tests and treatment. The impact of this pilot is described. METHODS: Access to care was measured using the proportion of villages targeted by the effort with active CHWs. Epidemiological impact was evaluated through standard surveillance and case management measures. Tests for differences in proportions or rates were used to compare measures prior to (October 2014-September 2016) and during the pilot (October 2016-September 2018). RESULTS: An active CHW was placed in 39 (95%) of 41 target communities. During the pilot, CHWs detected 61% of all reported cases from the region. Test positivity in the population tested by CHWs (22%) was higher than in those tested through active surveillance, both before (3.8%) and during the pilot (2.9%). From the pre-pilot to the pilot period, annual blood examination rates decreased (9.8 per 100 vs. 8.0 per 100), test positivity increased (4.2% to 8.5%, Χ2 = 126.3, p < 0.001) and reported incidence increased (4.1 cases per 1000 to 6.9 cases per 1000 [Incidence Rate Ratio = 1.83, 95% CI 1.52, 2.21]). The percent of cases tested on the day of symptom onset increased from 8 to 27% and those treated on the day of their test increased from 26 to 84%. CONCLUSIONS: The CHW network allowed for replacement of routine active surveillance with strong passive case detection leading to more targeted and timely testing and treatment. The higher test positivity among those tested by CHWs compared to active surveillance suggests that they detected cases in a high-risk population that had not previously benefited from access to diagnosis and treatment. Surveillance data acquired through this CHW network can be used to better target active case detection to populations at highest risk.