Blinded evaluation of commercial urinary lipoarabinomannan for active tuberculosis: a pilot study

Urine antigen testing is an attractive strategy for the diagnosis of active tuberculosis (TB), but accuracy data are scarce.

To prospectively evaluate the diagnostic performance of commercial urinary lipoarabinomannan (LAM) antigen testing for active TB among pulmonary and extra-pulmonary TB suspects.

Prospective blinded evaluation of 200 adult TB suspects at a tertiary referral hospital in India. Reference standards included culture and clinical diagnosis.

Patients were 61% male (mean age 40.4 years): 8.5% were human immunodeficiency virus (HIV) infected and 47 of 200 (23.5%) were culture-positive for TB. Compared to positivity on either Löwenstein-Jensen (LJ) or BACTEC cultures, LAM sensitivity was 17.8% (95%CI 8.5-32.6), while specificity was 87.7% (95%CI 81.3-92.3). Compared to positivity on both LJ and BACTEC, LAM sensitivity was 5.8% (95%CI 12.5-44.9), with a specificity of 88.8% (95%CI 82.7-92.9). Compared to the clinical diagnosis, LAM sensitivity was 20.0% (95%CI 1.1-70.1), with a specificity of 83.3% (95%CI 50.9-97.0). HIV and smear status did not influence test accuracy.

In its current form, LAM is insensitive for the diagnosis of active TB, although its specificity is adequate.