Blinded trial of multiplex serodiagnostic test in India for diverse forms of active tuberculosis

Rapid, high-throughput, and point-of-care tests to detect diverse major forms of active tuberculosis (TB) are urgently needed. Our blood test can fulfill that need. The blinded trial of the multiplex serodiagnostic test in India described here builds on our previously published field studies in diverse endemic regions (India, Uganda, and Pakistan). Antibody responses to Mycobacterium tuberculosis (M. tb.) were profiled in blood plasma using a multiplex test that comprised 12 M. tb. antigens. The samples included TB patients with adult pulmonary TB (APTB; including clinically diagnosed cases), extrapulmonary TB (EPTB), pediatric TB (PEDTB), and TB in HIV-positive individuals. Control groups included healthy individuals and lung disease patients, where TB was ruled out by liquid culture (disease controls). The results demonstrated the utility of our test across diverse forms of TB: microbiologically confirmed APTB, clinically diagnosed TB, PEDTB, and EPTB, with sensitivities of 90.8%, 52.2%, 87.0%, and 64.5%, respectively. The test demonstrated good specificity in control groups (healthy 90.3% and disease controls 78.4%). This non-sputum-based test detects diverse forms of TB with sensitivity and specificity better than the WHO Target Product Profile for a triage test. It is technology-platform agnostic and amenable to high-throughput and point-of-care applications.IMPORTANCESputum-based tests for tuberculosis (TB) have important limitations: smear microscopy has poor sensitivity; liquid culture, although the gold standard, is slow and only about 85% sensitive; and rapid molecular assays still rely on sputum. These limitations are especially pronounced in children, patients with extrapulmonary TB, HIV-TB, and individuals unable to produce sputum. In a blinded trial in India, we evaluated a simple blood test that detects antibodies to multiple Mycobacterium tuberculosis proteins. The test demonstrated high sensitivity across diverse forms of active TB, including adult pulmonary TB, extrapulmonary TB, pediatric TB, HIV-TB, and microbiologically negative TB, with good specificity in controls. With results available in approximately 2 h and no need to handle infectious sputum, this test demonstrates potential utility as a non-sputum, blood-based triage test in settings where sputum-based methods are inadequate.