Utility of urine lipoarabinomannan (LAM) in diagnosing tuberculosis and predicting mortality with and without HIV: prospective TB cohort from the Thailand Big City TB Research Network

Abstract

Objectives: To evaluate the applicability and accuracy of the urine lipoarabinomannan (LAM) test in tuberculosis (TB)/HIV co-infected patients and HIV-negative patients with disseminated TB.

Methods: Frozen urine samples obtained at baseline from patients in the TB research cohort with proven culture-positive TB were selected for blinded urine LAM testing. One hundred and nine patients were categorized into four groups: (1) HIV-positive patients with TB; (2) HIV-negative patients with disseminated TB; (3) HIV-negative immunocompromised patients with TB; and (4) patients with diseases other than TB. The sensitivity of urine LAM testing for culture-positive TB, specificity of urine LAM testing for patients without TB, positive predictive value (PPV), and negative predictive value (NPV) were assessed.

Results: The sensitivity of the urine LAM test in group 1 patients with a CD4 T-cell count of >100, ≤100, and ≤50 cells/mm³ was 38.5%, 40.6%, and 45%, respectively. The specificity and PPV of the urine LAM test were >80%. The sensitivity of the test was 20% in group 2 and 12.5% in group 3, and the specificity and PPV were 100% for both groups. A positive urine LAM test result was significantly associated with death.

Conclusions: This promising diagnostic tool could increase the yield of TB diagnosis and may predict the mortality rate of TB infection, particularly in TB/HIV co-infected patients.

Keywords: Acid-fast bacilli (AFB); Disseminated tuberculosis; HIV-infected patients; Tuberculosis; Urine lipoarabinomannan.