Performance of viral load as a marker for cryptococcal antigenemia screening among anti-retroviral therapy experienced human immunodeficiency virus infected patients at Baylor Uganda
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Background: Approximately 15% of all HIV-related deaths globally are attributable to Cryptococcal meningitis. Cryptococcal antigen (CRAG) screening and subsequent pre-emptive therapy can reduce the risk of Cryptococcal meningitis among HIV patients. Objective: To assess the performance of Viral Load (VL) as a marker for CRAG screening among Antiretroviral Therapy (ART) experienced HIV infected patients at the Baylor Uganda outpatient clinic. Methods: This was a cross sectional study conducted at Baylor-Uganda, Mulago hospital. Records of 798 HIV positive patients aged 10 years and above, on ART for at least 6month, with at least one viral load and a corresponding serum CRAG done between January 2017 and December 2018 and enrolled in the Baylor Cohort study were extracted from the Electronic Medical Records (EMR). Outcomes of the study were the prevalence of CRAG, sensitivity, specificity, and accuracy of VL as a marker for CRAG screening. The Gold standard was the Serum CRAG Lateral Flow Assay test. The analysis was done using 2x2 contingency tables and Receiver Operating Characteristic (ROC) curve analysis. Results: Prevalence of CRAG was 0.6% (95%CI: 0.2-1.5). The sensitivity and specificity of VL≥1000cp/ml were 20% and 99.4% respectively. The Area under the ROC curve (AUC) was 0.56 (95%CI: 0.29-0.82). The likelihood ratio positive and negative were 1.0. The optimal VL cut-off was VL≥49cp/ml with a sensitivity of 60% and specificity of 53%. Conclusion: The prevalence of CRAG in this population is very low. The performance of VL≥1000 as a marker for CRAG screening in this population is poor. The overall accuracy of VL is slightly above average. The optimal cut-off is VL≥49cp/ml. Recommendation: Uganda Ministry of Health should consider abandoning use of VL as a trigger for CRAG screening in populations with low CRAG prevalence or may consider lowering the trigger from treatment failure (VL≥1000cp/ml) to detectable VL (VL≥49cp/ml). A follow-on study in a population with a high CRAG prevalence should be conducted.