Journal of clinical microbiology 2017 08 09() pii 10.1128/JCM.00467-17
New non-sputum biomarker tests for active tuberculosis (TB) diagnostics are of highest priority for global TB control. We performed in-depth proteomic analysis using the 4000-plex SOMAscan assay on 1470 serum samples from seven TB-endemic countries. All samples were from patients with symptoms and signs suggestive of active pulmonary TB that were systematically confirmed or ruled-out for TB by culture and clinical follow-up. HIV-coinfection was present in 34%and 22% were sputum smear-negative. Serum protein biomarkers were identified by stability selection using L1-regularized logistic regression and by Kolmogorov-Smirnov (KS) statistics. A naïve Bayes classifier using six host response markers (HR6 model) including SYWC, kallistatin, complement C9, gelsolin, testican-2 and aldolase C performed well in a training set (AUC=0.94) and in a blinded verification set (AUC=0.92) to distinguish TB and non-TB. Differential expression was also highly significant (p<10(-20)) for previously described TB markers such as IP-10, LBP, FCG3B and TSP4, and for many novel proteins not previously associated with TB. Proteins with the largest median fold-change were SAA (serum amyloid protein A), NPS-PLA2 (secreted phospholipase A2), and CA6 (carbonic anhydrase 6). Target product profiles (TPPs) for a non-sputum biomarker test to diagnose active TB for treatment initiation (TPP#1) and for a community-based triage or referral test (TPP#2) have been published by the WHO. With 90% sensitivity and 80% specificity the HR6 model fell short of TPP#1, but reached TPP#2 performance criteria. In conclusion, we identified and validated a six-marker signature for active TB that warrants diagnostic development on a patient-near platform.