Detection of lipoarabinomannan in urine for identification of active tuberculosis among HIV-positive adults in Ethiopian health centres

Abstract

Objective: To assess the diagnostic performance of urine lipoarabinomannan (LAM) detection for TB screening in HIV-positive adults in Ethiopia.

Methods: Testing for LAM was performed using the Determine TB-LAM lateral flow assay on urine samples from participants in a prospective cohort with baseline bacteriological categorisation for active TB in sputum. Characteristics of TB patients with regard to LAM status were determined. Participants were followed for 6 months to evaluate survival, retention in care and incident TB.

Results: Positive LAM results were found in 78/757 participants. Among 128 subjects with definite (confirmed by culture and/or Xpert MTB/RIF) TB, 33 were LAM-positive (25.8%); the respective figure for clinically diagnosed cases was 2/20 (10%). Five of the remaining 43 LAM-positive individuals had died during the 6-month follow-up period, whereas 38 remained in care without clinical signs of TB. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 25.8%, 92.9%, 42.3% and 86.0%, respectively. Among TB patients, LAM positivity was associated with higher WHO clinical stage, lower body mass index (BMI), CD4 cell and haemoglobin levels, and with increased mortality. A combination algorithm of urine LAM testing and sputum smear microscopy detected 49 (38.2%) of definite TB cases; among those with CD4 count ≤100 cells/mm³ , this proportion was 66.7%.

Conclusions: The performance of urine LAM testing for TB detection was poor in this population. However, this was improved among subjects with CD4 count ≤100 cells/mm³ . In combination with sputum microscopy urine, LAM could be considered for targeted TB screening in this subgroup.

Keywords: ART; TAR; TB; Determinación TB-LAM; Determine TB-LAM; Ethiopia; Ethiopie; Etiopía; Lipoarabinomanano; antiretroviral therapy; centres de santé; centros sanitarios; determine TB-LAM; health centres; lipoarabinomannan; lipoarabinomannane; tuberculose.