LAUSR

BACKGROUND Targeted viral load (VL) testing has been proposed for antiretroviral treatment (ART) monitoring in resource-limited settings. In this study, we have investigated the performance of the host biomarker Galectin-9 (Gal-9), alone and in combination with interferon-γ-inducible protein 10 (IP-10), in identifying individuals at increased likelihood of viremia during ART. SETTING Cohort of HIV positive adults receiving ART at Ethiopian health centers. METHODS We included participants with detectable viremia (VL ≥150 copies/ml) 12 months after starting ART and sex-matched non-viremic controls. Performance to identify individuals with VL ≥1000 copies/ml was determined for Gal-9 and the Gal-9/IP-10 combination respectively, using receiver operating characteristics (ROC) analysis. RESULTS Among 191 participants (50.3% women), 46 (24.1%) had VL ≥1000 copies/ml, 23 (12.0%) 150-999 copies/ml and 122 (63.9%) <150 copies/ml. Gal-9 and VL were positively correlated (rs=0.451, p<0.001). Sensitivity and specificity for Gal-9 to identify individuals with VL ≥1000 copies/ml was 91.3% (95% CI, 79.2-97.6) and 54.5% (95% CI, 46.0-62.8) respectively. The area under the ROC curve for Gal-9 was 0.810 (95% CI, 0.745-0.875), which was similar to that of the combination of Gal-9 and IP-10 [0.849 (95% CI, 0.792-0.905)]. Assuming 10% prevalence of VL ≥1000 copies/ml, using Gal-9 for targeted VL testing instead of universal VL testing would reduce the number of VL tests from ten to five to identify one viremic individual, with misclassification in 1/10 viremic individuals. CONCLUSION Gal-9 is a potential screening marker for targeted VL monitoring in ART recipients. Further studies are needed to determine optimal threshold levels.