Rapid Low Cost Urine Test Diagnoses Tuberculosis, Reduces Mortality

HIV-associated tuberculosis is difficult to diagnose and results in high mortality and frequent extra-pulmonary presentation, inability to obtain sputum, and paucibacillary samples limits the usefulness of nucleic-acid amplification tests and smear microscopy.

A team of international scientists led by those at the University of Cape Town (South Africa) randomly allocated 2,528 patients with HIV from 10 hospitals in four countries in sub-Saharan Africa (four in South Africa, two in Tanzania, two in Zambia, and two in Zimbabwe) to receive either routine testing including smear, Xpert MTP/RIF (Cepheid, Sunnyvale , CA, USA) and culture, as well as the LAM urine-test (LAM group, 1,257 patients) or routine testing alone (no-LAM group, 1,271 patients).

All patients were asked to provide a urine sample of at least 30 mL at enrolment, and trained research nurses did the LAM test in patients allocated to this group using the Alere Determine tuberculosis LAM Ag lateral flow strip test (Alere; Waltham, MA, USA) at the bedside on enrolment. The LAM urine-test detects a glycolipid molecule (lipoarabinomannan), which is linked to TB. It provides a result in 25 minutes and each test costs about USD 2.66.

Eight weeks after being discharged from hospital, 21% (261) of patients in the LAM group had died compared to 25% (317) of patients in the non-LAM group, an absolute reduction of 4%. A greater proportion of patients in the LAM group (648; 52%) were treated for TB than in the no-LAM group (598; 47%). Those who started TB treatment, a higher proportion of patients were treated in the first three days in the LAM group (513/648; 79%) compared to the non-LAM group (413/598; 69%).

The effect of LAM testing on mortality varied by country but the highest sensitivity was found in people with the lowest CD4 cell count, a measure of how badly the immune system is damaged in patients with HIV, who are the hardest to diagnose with TB using routine testing. The authors found that the LAM urine-test had a sensitivity of 46% (the proportion of people with TB correctly diagnosed) and specificity of 90% (the proportion of healthy people who are correctly identified as healthy). The study was published on March 9, 2016, in the journal the Lancet.

Related Links:
University of Cape Town
Cepheid
Alere