Hepatitis C virus antigen detection is an appropriate test for screening and early diagnosis of hepatitis C virus infection in at-risk populations and immunocompromised hosts.

Early diagnosis remains key for effective prevention and treatment. Unfortunately, current screening with anti-hepatitis C virus antibody (anti-HCV Ab) test may have limited utility in the diagnosis of HCV infection and reinfection. This is of special concern to at-risk population, such as immunocompromised hosts and end-stage renal failure patients on hemodialysis. HCV antigen (Ag) could be useful in identifying the ongoing infection in such clinical scenarios. Hence, we aimed to study the utility of HCV Ag testing for the diagnosis of acute and chronic hepatitis C. Of 89 samples studied, 19 were from acute hepatitis C patients who were immunocompromised or were on hemodialysis, 43 were from active chronic hepatitis C patients and 27 were from patients treated for chronic hepatitis C. All samples were tested for HCV Ag using the Abbott ARCHITECT HCV Ag assay. HCV Ag was reactive in 19/19 samples from acute hepatitis C patients and 42/43 samples from active chronic hepatitis C patients. It was nonreactive in all samples from treated patients. The test showed a sensitivity and specificity of 98.4% and 100.0%, respectively. The positive and negative predictive values were 100.0% and 96.4%, respectively. The HCV antigen test has high clinical sensitivity and specificity and is useful for the diagnosis of acute and chronic hepatitis C infection in at-risk and immunocompromised patients. Its short turnaround time and relatively low cost are advantageous for use in patients on hemodialysis and other at-risk patients who require monitoring of HCV infection and reinfection.

Well-Based Antibody Arrays.

Multiplex immunoassays are important tools in basic research and diagnostics. The ability to accurately quantify the presence of several antigens within an individual sample all at once has been useful in developing a proteomics view of biology. This in turn has enabled the development of disease-associated immunodiagnostic panels for better prognosis and well-being. Moreover, it is well understood that such multiplexing approaches lend themselves to automation, thereby reducing labor while providing the ability to dramatically conserve both reagent and sample all of which will reduce the cost per test. Here we describe various methods to create and use multiplex immunoassays in the wells of microtiter plates or similar formats.

Allergy Testing - An Overview.

Childhood allergies pose huge economic burden and adverse effects on quality of life. Serum IgE has been considered a surrogate allergy marker for decades. Availability of several over-the-counter allergy tests add to confusion of partially trained caregivers. The present review focuses on current status of allergy testing in Indian scenario. Various in-vitro and in-vivo diagnostic modalities are available for allergy detection. Skin prick tests are useful for aero-allergies whereas oral challenge tests are best for identifying suspected food allergies. An allergy test should be individualized based on clinical features, diagnostic efficacy, and cost-benefit analysis.

Impact of Adopting Routine Luminex-Based Pretransplant Assessment of HLA Antibodies on Clinical Practice and Outcomes in Kidney Transplantation.

BACKGROUND: Accumulating evidence suggests that detection of human leukocyte antigen (HLA) antibodies by solid phase Luminex assays predicts renal allograft outcomes. However, several controversies exist regarding the interpretation, reproducibility, impact and financial feasibility of global utilization of this assay in pretransplant assessment. METHODS: We studied short-term patient-centered outcomes, medical standards of care, and financial plausibility of using Luminex-based screening for HLA antibodies in renal allograft recipients compared to outcomes in nontested patients. RESULTS: We included 1808 patients assessed for transplantation from 2011 to 2018. Luminex-tested patients had lower rates of rejection in the first post-transplant week (OR 0.36, P < .001) and lower odds of antibody-mediated rejection in the first 6 months (OR 0.4, P = .004). Forty-four patients with preformed, donor-specific antibodies were transplanted, and everolimus was introduced into our protocols for low-risk patients based on risk stratification by Luminex results. The number of tests needed to be performed to prevent 1 episode of antibody-mediated rejection in the first 6 months was 28 (P = .004), which was financially plausible. CONCLUSIONS: Routine pre-transplant assessment of HLA antibodies using Luminex assays may allow for better patient-centered, short-term graft outcomes and objective tailoring of immunosuppression at a financially plausible, cost-effective rate.

HCV core antigen comes of age: a new opportunity for the diagnosis of hepatitis C virus infection.

The diagnosis of hepatitis C virus (HCV) infection has been traditionally based on the detection of the host antibody response. Although antibody assays are available in different formats and are fairly accurate, they cannot distinguish between an ongoing infection with HCV replicative activity and a past infection where HCV has been cleared, spontaneously or after a successful therapy. As a chronic infection is mostly asymptomatic until the late clinical stages, there is a compelling need to detect active HCV infection by simple and reproducible methods. On this purpose, the clinical guidelines have suggested to search for the HCV ribonucleic acid (HCV-RNA) after anti-HCV has been detected, but this second step carries several limitations especially for population screening. The availability of fast and automated serological assays for the hepatitis C core antigen (HCVAg) has prompted an update of the guidelines that now encompass the use of HCVAg as a practical alternative to HCV-RNA, both for screening and monitoring purposes. In this paper, we summarize the features, benefits and limitations of HCVAg testing and provide an updated compendium of the evidences on its clinical utility and on the indications for use.

Sensitivity, specificity and comparison of three commercially available immunological tests in the diagnosis of Cryptosporidium species in animals

ABSTRACT The study was conducted to compare the specificity of immunological diagnostic methods used for the diagnosis of Cryptosporidium species capable of causing life-threatening infection in both immunosuppressed and immunocompetent patients. For the detection of Cryptosporidium species in 79 animals with diarrhoea, we used three Copro-antigen tests: RIDASCREEN® Cryptosporidium test, Cryptosporidium 2nd Generation (ELISA) and RIDA®QUICK Cryptosporidium. For immunoassays we used positive and negative samples detected by means of polymerase chain reaction and validated by sequencing and nested polymerase chain reaction to confirm the presence six different species of Cryptosporidium species. Prevalence of cryptosporidiosis in the entire group determined by enzyme immunoassay, enzyme linked immunosorbent assay, immuno-chromatographic test and polymerase chain reaction was 34.17%, 27.84%, 6.33% and 27.84%, respectively. Sensitivity of animal samples with enzyme immunoassay, enzyme linked immunosorbent assay, and immuno-chromatographic test was 63.6%, 40.9% and 22.7%, resp., when questionable samples were considered positive, whereas specificity of enzyme immunoassay, enzyme linked immunosorbent assay and immuno-chromatographic test was 75.9%, 78.9% and 100%, respectively. Positive predictive values and negative predictive values were different for all the tests. These differences results are controversial and therefore reliability and reproducibility of immunoassays as the only diagnostic method is questionable. The use of various Cryptosporidium species in diagnosis based on immunological testing and different results obtained by individual tests indicate potential differences in Copro-antigens produced by individual Cryptosporidium species.

Sensitivity, specificity and comparison of three commercially available immunological tests in the diagnosis of Cryptosporidium species in animals.

The study was conducted to compare the specificity of immunological diagnostic methods used for the diagnosis of Cryptosporidium species capable of causing life-threatening infection in both immunosuppressed and immunocompetent patients. For the detection of Cryptosporidium species in 79 animals with diarrhoea, we used three Copro-antigen tests: RIDASCREEN®Cryptosporidium test, Cryptosporidium 2nd Generation (ELISA) and RIDA®QUICK Cryptosporidium. For immunoassays we used positive and negative samples detected by means of polymerase chain reaction and validated by sequencing and nested polymerase chain reaction to confirm the presence six different species of Cryptosporidium species. Prevalence of cryptosporidiosis in the entire group determined by enzyme immunoassay, enzyme linked immunosorbent assay, immuno-chromatographic test and polymerase chain reaction was 34.17%, 27.84%, 6.33% and 27.84%, respectively. Sensitivity of animal samples with enzyme immunoassay, enzyme linked immunosorbent assay, and immuno-chromatographic test was 63.6%, 40.9% and 22.7%, resp., when questionable samples were considered positive, whereas specificity of enzyme immunoassay, enzyme linked immunosorbent assay and immuno-chromatographic test was 75.9%, 78.9% and 100%, respectively. Positive predictive values and negative predictive values were different for all the tests. These differences results are controversial and therefore reliability and reproducibility of immunoassays as the only diagnostic method is questionable. The use of various Cryptosporidium species in diagnosis based on immunological testing and different results obtained by individual tests indicate potential differences in Copro-antigens produced by individual Cryptosporidium species.

Greater Real-Life Diagnostic Efficacy of Allergen Molecule-Based Diagnosis for Prescription of Immunotherapy in an Area with Multiple Pollen Exposure.

BACKGROUND: Allergen molecule-based diagnosis has been suggested to facilitate the identification of disease-causing allergen sources and the prescription of allergen-specific immunotherapy (AIT). The aim of the current study was to compare allergen molecule-based IgE serology with allergen extract-based skin testing for the identification of the disease-causing allergen sources. The study was conducted in an area where patients are exposed to pollen from multiple sources (trees, grasses, and weeds) at the same time to compare the diagnostic efficiency of the 2 forms of diagnosis. METHODS: Patients from Astana, Kazakhstan, who suffered from pollen-induced allergy (n = 95) were subjected to skin prick testing (SPT) with a local panel of tree pollen, grass pollen, and weed pollen allergen extracts and IgE antibodies specific for marker allergen molecules (nArt v 1, nArt v 3, rAmb a 1, rPhl p 1, rPhl p 5, rBet v 1) were measured by ImmunoCAP. Direct and indirect costs for diagnosis based on SPT and marker allergen-based IgE serology as well as direct costs for immunotherapy depending on SPT and serological test results were calculated. RESULTS: The costs for SPT-based diagnosis per patient were lower than the costs for allergen molecule-based IgE serology. However, allergen molecule-based serology was more precise in detecting the disease-causing allergen sources. A lower number of immunotherapy treatments (n = 119) was needed according to molecular diagnosis as compared to extract-based diagnosis (n = 275), which considerably reduced the total costs for diagnosis and for a 3-year treatment from EUR 1,112.30 to 521.77 per patient. CONCLUSIONS: The results from this real-life study show that SPT is less expensive than allergen molecule-based diagnostic testing, but molecular diagnosis allowed more precise prescription of immunotherapy which substantially reduced treatment costs and combined costs for diagnosis and treatment.

New developments in the immunodiagnosis of brucellosis in livestock and wildlife.

Although relatively effective diagnostic tests for brucellosis have been in existence for more than 100 years, it remains a serious, embedded and also a re-emerging disease in many parts of the globe. There are many factors besides suboptimal diagnosis that impede the complete and sustained eradication of animal brucellosis. In this review a case for the continued improvement of diagnostic methods is made through identifying existing shortcomings and considering what impact these have upon control and eradication. The focus is on developments in immunodiagnostics as these seem more likely to yield the pragmatic solutions needed. Moreover, developments in DNA detection methods have been neatly and recently reviewed elsewhere. This article reviews issues such as test cost, mobility, sensitivity and specificity. Advances in low-cost materials, high-throughput testing, assay multiplexing and the quantification of pen-side tests are described and their relevance to disease control considered. Poor test specificity when resolving positive serology, due to infection with cross-reactive bacteria and vaccination with smooth Brucella strains, is also an impediment to efficient disease eradication. A case for the development of novel discrete epitope antigens to address this is presented alongside in silico methods of selection and tools that enable increased analytical sensitivity that may be required to detect relatively low, but potentially significant, analytes. References have been drawn from the study of brucellosis wherever possible. However, in some cases new technological developments worthy of discussion have been included via the use of pertinent alternative examples. In conclusion, despite developments and innovations the classical serological tests seem under no imminent danger of mass extinction but there is potential for significant improvement and supplementation.

Developing a framework for risk-based surveillance of tuberculosis in cattle: a case study of its application in Scotland.

Due to its substantially lower prevalence of bovine tuberculosis (bTB) relative to other areas of Great Britain, Scotland was designated as an officially (bovine) TB-free region in 2009. This paper investigates resultant possibilities for reducing surveillance by developing risk-based alternatives to current 4-year testing of eligible herds. A model of freedom of infection was used to develop strategies that specifically tested herds that are at risk of infection but would probably not be identified by slaughterhouse meat inspection. The performance of current testing is mimicked by testing all herds that slaughter fewer than 25% of their total stock per year and regularly import animals from high-incidence areas of England and Wales or from Ireland. This system offers a cost reduction by requiring 25% fewer herd and animal tests and 25% fewer false positives.

Determining safe alternatives for multidrug hypersensitive patients with the alternative triple antibiotic-analgesic test.

BACKGROUND: Drug provocation tests (DPTs) need technical equipment, staff and time. There are very few allergy centres performing DPTs in Turkey. Therefore many patients are referred to these centres. One day triple-double antibiotic or non-steroidal anti-inflammatory drug (NSAID) oral DPT for determining safe alternatives is safe, cost-effective and time saving compared to conventional one day one drug oral DPT. Our aim was to investigate the safety of antibiotic-NSAID oral DPT performed on the same day to find safe alternatives in multidrug hypersensitive patients. METHODS: Forty-two patients who had been diagnosed as having both antibiotic and NSAID hypersensitivity were enrolled to the study between 15 November and 15 July 2010. The reactions were urticaria and/or angio-oedema not including laryngeal oedema for all patients. Two antibiotics-one NSAID or two NSAIDs-one antibiotic triple test have been performed on the same day to study patients (n=22), while the control group (n=20) had taken drugs on three separate days. RESULTS: Only two patients had positive reactions during triple test and two patients had adverse reactions; one had gastric pain, one had nausea. Three patients in the control group had positive reactions. There were no significant differences between the two groups in frequency of adverse and allergic drug reactions (p>0.05). Sixty days were spent for the tests of the control group with only 28 days for the study population. CONCLUSION: Triple test performed with antibiotic and NSAID on the same day for determining safe alternatives for multidrug hypersensitive patients reporting non-life-threatening allergic reactions seems to be safe and time-saving.

Identification and discrimination of snake venoms from Egyptian elapids.

The avidity to the corresponding antigens is often higher than to the cross-reactive antigens. This was demonstrated with the highly cross-reactive elapid Egyptian snake venoms Naja haje (Nh), Naja nigricollis (Nn) and Walterinnesia aegyptia (Wa), and used for the differentiation among the three species in a simple ELISA-based assay. A three-step immuno-affinity protocol was followed and the titer and avidity of the different antibody (Ab) preparations were assessed and evaluated. The advantages offered by the avidity power of the venom specific antibodies (VS-Abs) obtained after one step purification, outweigh the specificity of the species-specific antibodies (SS-Abs) obtained after further purification. The efficiency of the VS-Abs as special immunodiagnostics was validated using 16 venom samples collected from individual snakes of different size and age at different time intervals. The avidities of the VS-Abs to the homologous venoms were 2.53 ± 0.4, 2.66 ± 0.31 and 2.8 ± 0.06 for Nh, Nn and Wa venoms respectively; whereas the avidity of the same Abs to the heterologous venoms could hardly exceed 1. Venom concentrations in the range between 10-1250 ng/well were detected with almost the same efficiency, an extra advantage that could be added to the assay to assure equal sensitivity allover the mentioned venom concentration range.

Rescreening of persons with a negative colonoscopy result: results from a microsimulation model.

BACKGROUND: Persons with a negative result on screening colonoscopy are recommended to repeat the procedure in 10 years. OBJECTIVE: To assess the effectiveness and costs of colonoscopy versus other rescreening strategies after an initial negative colonoscopy result. DESIGN: Microsimulation model. DATA SOURCES: Literature and data from the Surveillance, Epidemiology, and End Results program. TARGET POPULATION: Persons aged 50 years who had no adenomas or cancer detected on screening colonoscopy. TIME HORIZON: Lifetime. PERSPECTIVE: Societal. INTERVENTION: No further screening or rescreening starting at age 60 years with colonoscopy every 10 years, annual highly sensitive guaiac fecal occult blood testing (HSFOBT), annual fecal immunochemical testing (FIT), or computed tomographic colonography (CTC) every 5 years. OUTCOME MEASURES: Lifetime cases of colorectal cancer, life expectancy, and lifetime costs per 1000 persons, assuming either perfect or imperfect adherence. RESULTS OF BASE-CASE ANALYSIS: Rescreening with any method substantially reduced the risk for colorectal cancer compared with no further screening (range, 7.7 to 12.6 lifetime cases per 1000 persons [perfect adherence] and 17.7 to 20.9 lifetime cases per 1000 persons [imperfect adherence] vs. 31.3 lifetime cases per 1000 persons with no further screening). In both adherence scenarios, the differences in life-years across rescreening strategies were small (range, 30 893 to 30 902 life-years per 1000 persons [perfect adherence] vs. 30 865 to 30 869 life-years per 1000 persons [imperfect adherence]). Rescreening with HSFOBT, FIT, or CTC had fewer complications and was less costly than continuing colonoscopy. RESULTS OF SENSITIVITY ANALYSIS: Results were sensitive to test-specific adherence rates. LIMITATION: Data on adherence to rescreening were limited. CONCLUSION: Compared with the currently recommended strategy of continuing colonoscopy every 10 years after an initial negative examination, rescreening at age 60 years with annual HSFOBT, annual FIT, or CTC every 5 years provides approximately the same benefit in life-years with fewer complications at a lower cost. Therefore, it is reasonable to use other methods to rescreen persons with negative colonoscopy results. PRIMARY FUNDING SOURCE: National Cancer Institute.

Are anti-nucleosome antibodies a better diagnostic marker than anti-dsDNA antibodies for systemic lupus erythematosus? A systematic review and a study of metanalysis.

BACKGROUND: Methods to detect anti-nucleosome antibodies (ANuA) have been available for more than 10 years and the test has demonstrated its good sensitivity and high specificity in diagnosing systemic lupus erythematosus (SLE). Despite these data produced through clinical and laboratory research, the test is little used. OBJECTIVE: To verify the diagnostic performance of methods for measuring ANuA and to compare them with those for anti-dsDNA antibodies. DATA SOURCES: A systematic review of English and non-English articles using MEDLINE and EMBASE with the search terms "nucleosome", "chromatin", "anti-nucleosome antibodies" and "anti-chromatin antibodies". Additional studies were identified checking reference lists in the selected articles. STUDY SELECTION: We selected studies reporting on anti-nucleosome tests performed by quantitative immunoassays, on patients with SLE as the index disease (sensitivity) and a control group (specificity). A total of 610 titles were initially identified with the search strategy described. 548 publications were subsequently excluded based on abstract and title. Full-text review was undertaken as the next step on 62 publications providing data on anti-nucleosome testing; 25 articles were then excluded because they did not include either SLE patients or a control group, and 37 articles were selected for the metanalysis. Finally, a sub-metanalysis study was conducted on the 26 articles providing data on both ANuA and anti-dsDNA antibody assays in the same series of patients. DATA EXTRACTION: Extraction of data from selected articles was performed by two authors independently, using predefined criteria: the number of patients with SLE as the index case, and the number of healthy or diseased controls; specification of the analytical method used to detect anti-nucleosome and anti-dsDNA antibodies; the cut-off used in the study; and the sensitivity and specificity of the assay. Demographic and clinical data on the population investigated (adults or children; lupus patients with or without nephritis; patients with active or inactive disease) were also recorded and analyzed in a separate evaluation. RESULTS: The systematic review and metanalysis showed that the overall sensitivity of the ANuA assay is 61% (confidence interval-CI, 60-62) and the specificity 94% (CI, 94-95). The overall positive likelihood ratio is 13.81 (CI, 9.05-21.09) and the negative likelihood ratio 0.38 (CI, 0.33-0.44). The odds ratio for having SLE in ANuA-positive patients is 40.7. The comparative analysis on anti-dsDNA antibodies conducted on the 26 studies which provided data for both antibodies showed that ANuA have greater diagnostic sensitivity (59.9% vs 52.4%) and a specificity rating only slightly higher (94.9% vs 94.2%). The probability that a subject with positive ANuA have SLE is 41 times greater than a subject with negative ANuA, while for anti-dsDNA the probability is 28 times greater. These figures are even more impressive in children, in whom ANuA have an odds ratio for the diagnosis of SLE of 146, compared to 51 for anti-dsDNA antibodies. In selected studies, ANuA (p<0.0001) but not anti-dsDNA antibodies (p=0.256) were significantly associated with disease activity measured by the international score systems. However, neither antibody appears to correlate with kidney involvement. CONCLUSIONS: Data from the metanalysis have shown that ANuA have equal specificity but higher sensitivity and prognostic value than anti-dsDNA antibodies in the diagnosis of SLE. Despite a certain heterogeneity among the various studies, the use of ANuA appears more efficacious than anti-dsDNA.

Screening for colorectal cancer: what fits best?

Colorectal cancer (CRC) screening has been shown to be effective in reducing CRC incidence and mortality. There are currently a number of screening modalities available for implementation into a population-based CRC screening program. Each screening method offers different strengths but also possesses its own limitations as a population-based screening strategy. We review the current evidence base for accepted CRC screening tools and evaluate their merits alongside their challenges in fulfilling their role in the detection of CRC. We also aim to provide an outlook on the demands of a low-risk population-based CRC screening program with a view to providing insight as to which modality would best suit current and future needs.

Cost-effectiveness of mass screening for colorectal cancer: choice of fecal occult blood test and screening strategy.

BACKGROUND: Colorectal cancer is a major cause of mortality. This gives high public health priority to mass screening using a noninvasive, fecal occult blood test of asymptomatic individuals. A positive test selects those who should undergo colonoscopy to ensure early detection of colorectal cancer. Guaiac fecal occult blood test has low sensitivity. Automated immunochemical tests that measure the fecal human hemoglobin concentration are more sensitive and can be simplified as a 1- to 3-sample format with optimum cutoff points. OBJECTIVE: The aim was to improve the sensitivity of the test by choosing an accurate format (1- to 3-sample and optimum hemoglobin concentration) while maintaining acceptable specificity and avoiding alteration of the screening program in terms of quality of life and economic outputs. METHODS: We used a Markov model to estimate the cost-effectiveness of a screening program for a population of 100,000 asymptomatic individuals by use of immunological fecal tests with different cutoffs, leading to different sensitivity/specificity ratios, and to compare its incremental cost-effectiveness ratio compared with the guaiac fecal test program. RESULTS: The results suggest that a 3-sample immunological test with 50 ng/mL as a positive cutoff is cost-effective. It provides more asymptomatic cancer detection without significantly increasing normal colonoscopies. CONCLUSION: This format should be prospectively evaluated in mass screening.

[Immunodiagnosis and biomarkers in tuberculosis]. / Inmunodiagnóstico y biomarcadores en tuberculosis.

Based on the tuberculin skin test it is estimated that latent tuberculosis infection is present in one-third of the world's population. The new strategies in public health and research are aimed to reduce and eradicate this enormous reservoir. However, the absence of effective biomarkers for diagnosis and treatment of latent tuberculosis limits the development of new drugs and vaccines. Some components are present in both, the PPD (used in the tuberculin skin test) and the BCG vaccine. This increases the number of false positives in vaccinated individuals. Nowadays, there is not an immune diagnostic method that can differentiate latent tuberculosis and tuberculosis disease. New studies have addressed some strategies including specific antibodies, new cytokines and / or antigens as candidates for biomarkers. However, the high costs of these studies, the low number of participants and their different methodology make difficult a future meta-analysis and more conclusive results.