Evaluation of feasibility and utility of urinary lipoarabinomannan assay against conventional sputum microscopy in the detection of tuberculosis among people with and without HIV infection

Background

Tuberculosis (TB) is a major global public health challenge. Lipoarabinomannan (LAM) assessment in urine is a potential molecular diagnostic tool for TB.

Methods

We evaluated the feasibility and utility of urinary LAM in detecting TB along with sputum smear microscopy (SSM) and the TrueNAT test. In an observational cross-sectional pilot study, we collected sputum and urine samples from 240 subjects visiting the Designated Microscopy Center, Warangal during Apr-Sep 2021. LED microscopy, TrueNAT and liquid culture were performed on sputum while LAM test was conducted on urine samples.

Results

Mean age of the subjects was 45.1 (SD = 16.1) years. The majority were men (66 %), married (89 %) and urban (52 %) subjects. Overall sensitivity of urine LAM was 63.6 % and specificity 80.1 % while that of LED microscopy were 59.6 % and 56.7 % respectively. TrueNAT had sensitivity of 58.6 % and specificity of 80.1 %. However, a combination of LAM + TrueNAT had 79.8 % sensitivity. Among PLHIV, LAM + SSM has better sensitivity than any other combination of these tests or alone across all CD4 count categories.

Conclusion

Urinary LAM can be a more useful, feasible and better TB diagnostic biomarker over LED microscopy in diagnosing TB among the subjects who have symptoms irrespective of HIV status and recommend further evaluation of next-generation urinary LAM diagnostics to reach the unreached through a point of care tool.