Optimización de recursos para determinar la carga viral de HIV-1 en un país con pocos recursos / Optimizing resources to reduce costs to determine HIV viral load in limited resources settings

Resumen Introducción. Las metas globales para controlar la epidemia de HIV contemplan que la carga viral sea indetectable en 90 % de las personas en tratamiento. El costo de la medición de la carga viral en lotes de muestras puede reducirse y, así, aumentar la cobertura cuando los recursos son limitados; sin embargo, su eficacia disminuye al aumentar la prevalencia del fracaso del tratamiento antirretroviral. Objetivo. Evaluar estrategias para disminuir la proporción de pacientes con fracaso del tratamiento antirretroviral en los lotes de muestras y, de esta manera, aumentar el ahorro en las pruebas de carga viral. Materiales y métodos. Las estrategias evaluadas fueron: a) la organización de los lotes de muestras según el esquema de tratamiento antirretroviral, y b) la exclusión de aquellos pacientes con antecedente reciente de fracaso del tratamiento antirretroviral, aquellos con menos de 12 meses de tratamiento antirretroviral y aquellos sin tratamiento antirretroviral previo. Los resultados de los lotes se compararon con los resultados individuales. Resultados. El valor diagnóstico negativo fue similar para los pacientes con esquema de primera línea (100,0 %; IC95% 99,5-100,0) o de segunda línea de tratamiento (99,4 %; IC95% 96,9-99,9). La incidencia del fracaso del tratamiento antirretroviral fue menor en los pacientes con tratamiento de primera línea (p<0,01), lo cual permitió un mayor ahorro en las pruebas de laboratorio en este grupo (74,0 %; IC95% 71,0-76,7) que en los pacientes con tratamiento de segunda línea (50,9 %; IC95% 44,4-57,3) (p<0,01). Conclusión. La selección de las muestras que se incluyeron en los lotes para determinar la carga viral del HIV según el tipo de esquema de tratamiento, permitió maximizar el porcentaje de ahorro en pruebas de laboratorio.

Abstract Introduction: HIV viral load testing is a key factor to evaluate the accomplishment of the UNAIDS target of 90% of viral suppression among people receiving antiretroviral therapy. Pooled samples are a potentially accurate and economic approach in resource-constrained settings, but efficiency can be negatively affected by high prevalence rates of virological failure. Objective: Strategies were assessed to increase the relative efficiency of pooled HIV viral load testing in resource-constrained settings. Materials and methods: We evaluated two strategies: a) plasma samples were not included in pools if patients had <12 months on antiretroviral therapy, patients had previous viral load >1,000 copies/ml, or were antiretroviral therapy naïve patients, and b) plasma pools were organized separately for first and second-line antiretroviral therapy regimens. Individual viral load tests were used to compare pooled results. Results: Negative predictive values were similar for patients on first (100.0%; 95% CI 99.5 to 100.0) and second-line antiretroviral therapy regimens (99.4%; 95% CI 96.9 to 99.9). However, the incidence of virological failure among individuals on first-line antiretroviral therapy was lower than second-line antiretroviral therapypatients (p <0.01), resulting in greater savings in laboratory tests in patients on first-line antiretroviral therapy (74.0%; 95% CI 71.0 to 76.7) compared with the group of patients on second-line antiretroviral therapy (50.9%; 95% CI 44.4 to 57.3) (p<0.01). Conclusion: Selecting the samples to be included in the pools and selecting the pools according to ART regimens are criteria that could lead to decreased spending on laboratory tests for HIV viral load determination in resource-constrained settings.

A robust HIV-1 viral load detection assay optimized for Indian sub type C specific strains and resource limiting setting

BACKGROUND: Human Immunodeficiency Virus Type 1 (HIV-1) viral load testing at regular intervals is an integral component of disease management in Acquired Immunodeficiency Syndrome (AIDS) patients. The need in countries like India is therefore an assay that is not only economical but efficient and highly specific for HIV-1 sub type C virus. This study reports a SYBR Green-based HIV-1 real time PCR assay for viral load testing and is designed for enhanced specificity towards HIV-1 sub type C viruses prevalent in India. RESULTS: Linear regression of the observed and reference concentration of standards used in this study generated a correlation coefficient of 0.998 (p<0.001). Lower limit of detection of the test protocol was 50 copies/ml of plasma. The assay demonstrated 100% specificity when tested with negative control sera. The Spearman coefficient of the reported assay with an US-FDA approved, Taqman probe-based commercial kit was found to be 0.997. No significant difference in viral load was detected when the SYBR Green based assay was used to test infected plasma stored at -20°C and room temperature for 7 days respectively (Wilcoxon signed rank test, p=0.105). In a comparative study on 90 pretested HIV-1 positive samples with viral loads ranging from 5,000 - 25,000 HIV-1 RNA copies/ml and between two commercial assays it was found that the later failed to amplify in 13.33% and 10% samples respectively while in 7.77% and 4.44% samples the copy number values were reduced by >0.5 log value, a figure that is considered clinically significant by physicians. CONCLUSION: The HIV-1 viral load assay reported in this study was found to be robust, reliable, economical and effective in resource limited settings such as those existing in India. PCR probes specially designed from HIV-1 Subtype C-specific nucleotide sequences originating from India imparted specificity towards such isolates and demonstrated superior results when compared to two similar commercial assays widely used in India.

Sangre segura en ausencia de infecciones virales por VHB, VHC y VIH en período de ventana serológica de donadores

OBJETIVO: Determinar la prevalencia de infecciones virales (VHB, VHC y VIH) en período de ventana serológica en donadores de sangre evaluados con la prueba de ácidos nucleicos (NAT). MATERIALES Y MÉTODOS: Se incluyeron donadores de sangre evaluados de 2008 a 2009 con pruebas serológicas y moleculares del VHB, VHC y VIH. El período de ventana serológica se definió con la prueba de NAT positiva y la prueba serológica negativa. RESULTADOS: Durante un año se evaluaron 47 847 donadores de sangre; no se identificó ningún caso con infección viral (VHB, VHC y VIH) en período de ventana serológica; únicamente se demostró NAT positivo en donadores con pruebas serológicas positivas: 26 de 78 con VHB, 56 de 318 con VHC y 16 de 155 con VIH. CONCLUSIÓN: Este es el primer estudio en México que demostró en donadores de sangre la ausencia de infecciones virales (VHB, VHC y VIH) en período de ventana serológica con la prueba de NAT.

OBJECTIVE: To determine the prevalence of viral infections (HBV, HCV and HIV) in serological window period in blood donors screened with nucleic acid testing (NAT). MATERIALS AND METHODS: We assessed all blood donors from July 2008 to June 2009 at the Central Blood Bank of the Mexican Institute of Social Security. Medical history was made and provided an information brochure and self-exclusion questionnaire. All blood donors were tested with serological tests (Ag-HBVs, Anti-HCV and Anti-HIV) and molecular testing with NAT for HBV, HCV and HIV. The window period was defined with the positive NAT and negative serological test. RESULTS: During one year, we evaluated 47 847 blood donors. None subject was identified with viral infection (HBV, HCV and HIV) in serological window period. Positive serological testing were found for HBV in 78 (0.2 percent), 318 (0.7 percent) for HCV and 155 (0.3 percent) for HIV. Positive NAT was demonstrated only in donors with positive serology: 26 of 78 with HBV, 56 of 318 with HCV and 16 of 155 with HIV. CONCLUSION: This is the first study in México showed no viral infections (HBV, HCV and HIV) during serological window period in blood donors; The medical history and the self-exclusion questionnaire help to improve blood transfusion safety.