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

- The urine lipoarabinomannan (LAM) test is especially helpful in cases where the smear result is negative in a probable TB patient and also in severely ill patients, regardless of HIV infection status, from whom it is difficult to physically collect sputum.
- The positive predictive value (PPV) was over 80% for those infected with HIV and up to 100% in non-HIV-infected patients. A high PPV can accurately guide the physician to confidently prescribe TB medications, which is particularly crucial among co-infected patients who are severely ill.
- This study found that a positive urine LAM test result was significantly associated with death, especially in those with an advanced HIV infection.
- The findings from this study suggest the possible use of the urine LAM test with acid-fast bacillus smear and culture in resource-limited countries, in the diagnosis of TB in patients with advanced HIV and in HIV-negative patients with disseminated TB.

SummaryObjectivesTo 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.MethodsFrozen 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.ResultsThe 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.ConclusionsThis 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.