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

Abstract

To assess the diagnostic performance of urine lipoarabinomannan (LAM) detection for TB screening in HIV-positive adults in Ethiopia. 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 6months to evaluate survival, retention in care and incident TB. 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 ≤100cells/mm3 , this proportion was 66.7%. The performance of urine LAM testing for TB detection was poor in this population. However, this was improved among subjects with CD4 count ≤100cells/mm3 . In combination with sputum microscopy urine, LAM could be considered for targeted TB screening in this subgroup.