Sensitivity and specificity of rapid hepatitis C antibody assays in freshly collected whole blood, plasma and serum samples: A multicentre prospective study.

BACKGROUND: This study evaluated performance of two hepatitis C virus (HCV) rapid diagnostic tests (RDTs) performed by intended users in resource-limited settings. METHODS: Testing was conducted at three facilities in two countries (Georgia, Cambodia) using matched fingerstick whole blood, plasma and serum samples. Investigational RDTs were compared with a composite reference standard (CRS) comprised of three laboratory tests, and a reference RDT. RESULTS: In matched samples from 489 HCV positive and 967 HCV negative participants, specificity with both investigational RDTs was high using either reference method (≥98.4% in all sample types). Sensitivity was lower in whole blood versus plasma and serum for both RDTs compared with the CRS (86.5-91.4% vs 97.5-98.0% and 97.3-97.1%) and reference RDT (93.6-97.8% vs 100% and 99.4%). Sensitivity improved when considering only samples with detectable HCV viral load. CONCLUSION: Sensitivity was highest in serum and plasma versus whole blood. The World Health Organization prequalification criterion (≥98%) was narrowly missed by both RDTs in serum, and one in plasma, possibly due to the intended user factor. Performance in whole blood was considered adequate, given potential roles of HCV infection history, improved sensitivity with detectable viral load and performance similarities to the reference RDT.

The added value of a CD4 count to identify patients eligible for highly active antiretroviral therapy among HIV-positive adults in Cambodia.

In a retrospective study of 648 persons with HIV infection in Cambodia, we determined the sensitivity, specificity, and accuracy of the 2003 World Health Organization (WHO) criteria to start antiretroviral treatment based on clinical criteria alone or based on a combination of clinical symptoms and the total lymphocyte count. As a reference test, we used the 2003 WHO criteria, including the CD4 count. The 2003 WHO clinical criteria had a sensitivity of 96%, a specificity of 57%, and an accuracy of 89% to identify patients who need highly active antiretroviral therapy (HAART). In our clinic, with a predominance of patients with advanced disease, the 2003 WHO clinical criteria alone was a good predictor of those needing HAART. A total lymphocyte count as an extra criterion did not improve the accuracy. Nine percent of patients were wrongly identified to be in need of HAART. Among them, almost 50% had a CD4 count of more than 500 cells/muL, and 73% had weight loss of more than 10% as a stage-defining condition. Our data suggest that, in settings with limited access to CD4 count testing, it might be useful to target this test to patients in WHO stage 3 whose staging is based on weight loss alone, to avoid unnecessary treatment.