The importance of prevalence and pre-test probability on the microbiological diagnosis of SARS-CoV-2: the case of Spain in 2020 / La importancia de la prevalencia y de la probabilidad pre-test en el diagnóstico microbiológico de SARS-CoV-2: el caso de España en 2020

Objectives. The aim of this work was to estimate the con ditioned probability for the diagnosis of SARS-CoV-2 infection with reverse transcription polymerase chain reaction (RT-PCR), viral antigen rapid diagnostic tests (Ag-RDT), and antibody detection tests depending on the prevalence in the specific healthcare settings in Spain in 2020, and on the pre-test prob ability (PTP) according to the clinical situation, age and un known or close contacts of the patient. Material and methods. Performance parameters of tests were obtained from literature. Prevalence data and PTP were obtained from Spanish sources and a survey, respectively. The post-test probability is the positive predictive value (PPV) when test is positive. For negative result, we also calculated the probability of having the infection (false negatives). Results. For both RT-PCR and viral Ag-RDT, the lowest PPV values were for the population screenings. This strategy proved to be useful in ruling out infection but generates a high number of false positives. At individual level, both tools provided high PPV (≥ 97%) when the PTP values are over 35%. In seroprevalence studies, though the specificity of IgG alone tests is high, under low seroprevalence, false positives cannot be avoided. Total antibodies tests are useful for diagnosis of COVID-19 in those doubtful cases with RT-PCR or Ag-RDT tests being repeatedly negative. Conclusions. The interpretating of results depends not only on the accuracy of the test, but also on the prevalence of the infection in different settings, and the PTP associated to the patient before performing the test (AU)

bjetivos. En este trabajo estimamos la probabilidad con dicionada del diagnóstico de infección por SARS-CoV-2 con RT PCR, pruebas de antígenos virales (Ag-RDT) y pruebas de detec ción de anticuerpos, en función de la prevalencia en España en diferentes ámbitos durante 2020, y de la probabilidad pre-test (PPT) según la situación clínica, edad y contactos del paciente. Material y métodos. Los parámetros de rendimiento de las pruebas se obtuvieron de bibliografía. Los datos de preva lencia y PPT se obtuvieron de fuentes españolas y de una en cuesta, respectivamente. La probabilidad post-test es el valor predictivo positivo (VPP) cuando la prueba es positiva. Para el resultado negativo, también calculamos la probabilidad de te ner la infección (falsos negativos). Resultados. Tanto con RT-PCR como con Ag-RDT, los va lores más bajos de VPP se detectaron en los cribados poblacio nales, que demostraron ser útiles para descartar la infección, pero generan muchos falsos positivos. A nivel individual, am bas pruebas proporcionaron un VPP ≥ 97% cuando los valores de PPT son superiores al 35%. En estudios de seroprevalencia, aunque la especificidad de las pruebas de IgG sola es alta, si la seroprevalencia es baja, no se pueden evitar falsos positivos. Además, las pruebas de anticuerpos totales pueden ayudar al diagnóstico de COVID-19 en aquellos casos dudosos con prue bas de RT-PCR o Ag-RDT repetidamente negativas. Conclusiones. La interpretación de los resultados depen de no sólo del rendimiento de las pruebas, sino también de la prevalencia de la infección en diferentes ámbitos, y de la PPT asociada al paciente antes de realizar la prueba (AU)

Uso de pruebas de diagnóstico rápido en la selección de donantes de plasma convaleciente Covid-19 / Use of rapid diagnostict test to select Covid-19's convalecent plasma donors

El uso de Plasma de Convaleciente de COVID-19 (PC-CoV19) como coadyuvante en el tratamiento de pacientes, tendría impacto socioeconómico importante al disminuir el periodo de estancia hospitalaria y letalidad por la enfermedad. La determinación de anticuerpos en plasma de potenciales donantes es criterio fundamental para su selección. Existe dificultad para disponer de pruebas serológicas certificadas que cuantifiquen anticuerpos específicos contra SARS-CoV-2. Las Pruebas de Diagnóstico Rápido (PDR) se convierten en herramienta útil y al alcance para la selección de pacientes recuperados, potenciales donantes de PC-CoV19. Este estudio evaluó el porcentaje de positividad de diferentes PDR en veintidós (22) muestras de pacientes con COVID-19 confirmada por RT-PCR. Las muestras se analizaron siguiendo el procedimiento descrito por cada fabricante. Se analizó el comportamiento de las PDR en pacientes sintomáticos y asintomáticos en diferentes momentos de la enfermedad. El porcentaje de positividad fue de 100% con dos de las tres pruebas utilizadas, una de las cuales discrimina IgM de IgG. Se concluye que la presencia de IgG se registra a partir de los 15 días del inicio de los síntomas y se mantiene presente a los 59 días de evolución en los pacientes sintomáticos, y que pacientes asintomáticos podrían ser considerados candidatos a donantes de PC-CoV19 pues se evidenció seroconversión para IgG. El porcentaje de positividad a IgG podría disminuir en los pacientes recuperados. Se sugiere que pacientes sintomáticos con criterio de alta médica sean considerados candidatos donantes en momento posterior a 28 días de la fecha de inicio de los síntomas. Se recomienda utilizar PDR que discriminen IgM de IgG como herramienta para la selección de donantes de PC-CoV19(AU)

The use of COVID-19 Convales-cent Plasma (PC-CoV19) as an ad-juvant for the treatment of patients, would have a significant socioeconomic impact by reducing the leng-th of hospital stay and lethality due to the disease. The determination of antibodies in plasma from potential donors is a fundamental criterion for their selection. There is dificulty in obtaining certified serological tests that quantify specific antibodies against SARS-CoV-2. Rapid Diagnostic Tests (PDR) become a useful and accessible tool in the selection of recovered patients, potential PC-CoV19 donors. This study evaluated the positivity rate of different PDRs in twenty two (22) samples from patients with COVID-19 confirmed by RT-PCR. The samples were analyzed following the procedure described by each manufacturer. The performance of PDRs was analyzed in symptomatic and asymptomatic patients at different times of the disease. The positivity rate was 100% with two of the three tests used, one of which discriminates IgM from IgG. It is concluded that the presence of IgG is recorded 15 days after the onset of symptoms and remains present at day 59 of evolution in symptomatic patients, and that asymptomatic patients could be considered candidates for PC-CoV19 donors since IgG se-reconversion was evident. The positivity rate to IgG could decrease in the recovered patients. It is suggested that symptomatic patients with medical discharge criteria be considered donor candidates after 28 days from the date of onset of symptoms. It is recommended to use PDRs that discriminate IgM from IgG as a tool for the selection of PC-CoV19 donors

Plasma de convaleciente para el tratamiento de la COVID-19: Protocolo para el acceso y uso en Venezuela / Convalescent Plasma for the Treatment of COVID-19: Protocol for access and use in Venezuela

En diciembre 2019, en Wuhan, China, se registró un aumento inusual de casos de infección respiratoria aguda de rápida progresión y alta letalidad. Al poco tiempo es identificado el agente causal, un coronavirus denominado SARS-CoV-2 y se caracteriza una nueva enfermedad, COVID-19. En ausencia hasta el momento de tratamientos específicos, eficaces y seguros, se justifica explorar alternativas científicamente fundamentadas a nuestro alcance como el uso de Plasma de Convaleciente (PC-CoV19) como coadyuvante para el tratamiento de la COVID-19. El plasma de pacientes recuperados de una enfermedad infecciosa, Plasma de Convaleciente, ha sido utilizado en el tratamiento de patologías infecciosas. Hay antecedentes inmediatos de su uso en enfermedades producidas por otro tipo de coronavirus y se registran experiencias y estudios clínicos con resultados preliminares durante esta pandemia. Quimbiotec, empresa productora de hemoderivados y fármacos recombinantes del Estado venezolano, y el Banco Municipal de Sangre, definen un protocolo para promover condiciones para la aféresis, procesamiento, conservación, almacenamiento, distribución, transfusión y evaluación de la seguridad y eficacia del PC-CoV19 como alternativa en el tratamiento de la COVID-19 en Venezuela. Se incluye la identificación de capacidades y de talento, la estructura física, equipos y especialistas necesarios, así como la definición de procesos para establecer rutinas controladas y auditables para sentar bases del acceso y uso del PC-CoV19 en el Sistema Nacional de Salud de Venezuela y preparar el diseño y ejecución de estudios clínicos. Se presenta el Protocolo y algunos nudos críticos en su ejecución a la fecha, herramientas y estrategias utilizadas para su solución(AU)

On December 2019, in Wuhan, China, there was an unusual increase in cases of a fast-progressing acute respiratory infection with high fatality rate. Soon after, the causing agent is identiied, a coronavirus called SARS-CoV-2, and a new disease, COVID-19 is characterized. Currently, in the absence of specific, effective and safe treatments, it is justified to explore all scientifically based alternatives available to us, such as the use of Convalescent Plasma (PC-CoV19) as acoadjutant treatment of COVID-19.Plasma from patients who have recovered from an infectious disease, Convalescent Plasma, has been used in the treatment of other infectious disease. There is recent history of its use in diseases caused by another type of coronavirus, and clinical experiences and studies have already been published with preliminary results during this pandemic. Quimbiotec, a Venezuelan State public company that produces blood products and recombinant drugs, and Banco Municipal de Sangre, deined a protocol to promote conditions for aphaeresis, processing, conservation, storage, distribution, transfusion, and evaluation of safety and eficacy of PC-CoV19 as an alternative for the treatment of COVID-19 in Venezuela. This protocol includes identification of capacities, physical structure, equipment and skills, talent, professionals needed, as well as a definition of processes to establish controlled and auditable routines to lay the foundations for access and use of PC-CoV19 in the Venezuela Health System, and prepare the design and implementation of clinical studies. The protocol and currently critical points in its implementation, as well as tools and strategies used for its solution, are presented(AU)

Use of point-of-care tests and antibiotic prescribing in sore throat and lower respiratory infections by general practitioners.

INTRODUCTION: This study was aimed at assessing general practitioners' (GP) reliance on patient history, examination findings and the influence of the utilisation of point-of-care tests (POCT) in antibiotic prescribing for sore throat and lower respiratory tract infections (LRTI). METHODS: Audit-based study carried out in 2015. A group of GPs received an intervention six years earlier with provision of POCTs and another group of GPs acted as controls. Odds ratios for clinical variables predicting antibiotic prescribing were calculated by logistic regression analyses. RESULTS: A total of 238 GPs included 1906 patients with sore throat and 1970 LRTIs. A negative POCT result was negatively associated with antibiotic prescribing, with odds ratios ranging from 0.09 to 0.23. GPs using POCTs attached less weight to clinical criteria. CONCLUSION: GPs using rapid tests are mainly influenced by POCT results in the decision to prescribe antibiotics. However, antibiotic prescribing is still observed with negative POCT results.

Diagnostic performance of rapid diagnostic tests for the diagnosis of malaria at public health facilities in north-west Ethiopia.

OBJECTIVE: To assess the performance of RDTs against nested polymerase chain reaction (nPCR) for the diagnosis of malaria in public health facilities in north-western Ethiopia. METHODS: Cross-sectional study at public health facilities in North Gondar, Ethiopia, of 359 febrile patients with signs and symptoms consistent with malaria. Finger prick blood samples were collected for testing in a P. falciparum/pan-malaria RDTs and for molecular analysis. Sensitivity, specificity and predictive values were determined for the RDTs using nPCR as reference diagnostic method. Kappa value was determined to demonstrate the consistency of the results between the diagnostic tools. RESULTS: By RDTs, 22.28% (80/359) of patients tested positive for malaria, and by nPCR, 27.02% (97/359) did. In nPCR, 1.67% (6/359) and 0.28% (1/359) samples were positive for P. ovale and P. malariae, which had almost all tested negative in the RDTs. The sensitivity, specificity, positive and negative predictive values of RDTs for the diagnosis of malaria were 62.9%, 92.7%, 76.3% and 87.1%, respectively, with 0.589 measurement agreement between RDTs and nPCR. The sensitivity and specificity of RDTs for P. falciparum identification only were 70.8% and 95.2%, and 65.2% and 93.1% for P. vivax. CONCLUSION: Although RDTs are commonly used at health posts in resource-limited environments, their sensitivity and specificity for the detection and species identification of Plasmodium parasites were poor compared to nPCR, suggesting caution in interpreting RDTs results. Particularly, in the light of expanded efforts to eliminate malaria in the country, more sensitive diagnostic procedures will be needed.