Background Detection of mycobacterial lipoarabinomannan antigen in urine has emerged as a potential point-of-care test for diagnosis of tuberculosis. This study aimed to evaluate the accuracy of the lateral flow urine lipoarabinomannan (LF-LAM) assay for diagnosis of active tuberculosis among Thai adults with advanced human immunodeficiency virus (HIV) infection. Methods HIV-infected adult patients with CD4 cell counts ≤200/μL and symptoms suggestive of active tuberculosis were prospectively recruited from both inpatient and outpatient settings at Siriraj Hospital and Chonburi Hospital in Thailand during the study period from December 2015 to March 2017. Freshly collected urine samples were applied to the Alere Determine TB LAM Ag test strip using a grade 1 cutoff, according to the manufacturer’s grading system. The diagnostic accuracy of the LF-LAM test was assessed against a microbiological reference standard (definite tuberculosis) or a composite reference standard (definite and probable tuberculosis). Results Of the 280 patients who were included, 72 (25.7%) had definite and 65 (23.2%) had probable tuberculosis. Among patients with definite tuberculosis, the LF-LAM test yielded a sensitivity of 75.0% and a specificity of 76.0%. It had the highest sensitivity (90.5%) in HIV-infected patients with CD4 cell counts <50/μL. It yielded a lower sensitivity (61.3%) but a higher specificity (86.0%) when compared with the composite reference standard. Among the 20 patients (14%) with false-positive results, strong band intensity was observed mostly in Mycobacterium avium complex infections. An incremental sensitivity of 11% was observed with use of acid-fast bacilli sputum smear or LF-LAM testing, compared with LF-LAM testing alone. Conclusions The LF-LAM test performed well in the diagnosis of active tuberculosis in selected patients with more advanced tuberculosis and coexisting HIV disease.

BackgroundEarly diagnosis and treatment of active tuberculosis (TB) in HIV-positive patients is challenging. Tests based on the detection of mycobacterial lipoarabinomannan (LAM) antigen in urine have emerged as potential point-of-care tests for TB. However, limited data exists on their performance among HIV-TB co-infected patients from Southeast Asian countries.MethodsWe prospectively recruited HIV-positive adult patients with CD4 count less than or equal to 200/mm3 and symptoms suspected of active TB from two tertiary hospitals between December 2015 and March 2017. Freshly collected urine was applied to the Determine®-TB LAM Ag test strip (4 bands of graded intensity), using grade 1 cutoff. Diagnostic accuracy of urine LAM strip test were assessed against microbiological reference standard, defined as positive Mycobacterium tuberculosis cultured from one or more clinical specimens (definite TB) or composite reference standard including definite TB and probable TB, defined as those have symptoms consistent with TB and response to anti-TB treatment.ResultsA total of 280 patients were enrolled. Of whom, 72 (25.7%) and 65 (23.2%) had definite and probable TB. Amongst those with definite TB, LF-LAM test gave a sensitivity of 75.0% (95% CI 63.9–83.6), specificity of 86.0% (95% CI 79.4–90.8) and accuracy of 82.3% (95% CI 76.7–86.8). When compared with the composite reference standard, the test yielded a lower sensitivity (61.3%, 95% CI 53.0–69.1) and accuracy (73.9%, 95% CI 68.5–78.7), with equal specificity. The test showed the highest sensitivity (90.5%, 95% CI 77.9–96.2) and accuracy (85.9%, 95% CI 79.2–90.7) but lower specificity (84.0%, 95% CI 75.6–89.9) in HIV-infected patients with CD4 count less than 50/mm3. The sensitivity of the combined LF-LAM or sputum microscopy was higher than that of either test alone (86.1% vs. 75.0%, 61.1%, respectively). Mycobacterium avium complex (MAC) was cultured in 7 out of 20 with false positive result. Urine LAM strip test can remain positive for up to 4 weeks even after anti-TB treatment.ConclusionUrine LAM assay gave the best performance for diagnosis of active TB in advanced HIV-infected patients and provide an additional benefit of a greater simplicity, speed, with a more easily obtainable sample.Disclosures All authors: No reported disclosures.