Microbial biomarkers of tuberculosis infection and disease in blood: systematic review and meta-analysis

BackgroundNumerous studies reporting utility of microbial blood biomarkers for diagnosis and treatment monitoring of M. tuberculosis (Mtb) infection and tuberculosis disease have been conducted, but up-to-date systematic reviews and meta-analyses of these data are lacking. We aimed to evaluate diagnostic accuracy of microbial blood biomarkers for detection of tuberculosis disease and to characterise their responses to antimicrobial therapy. MethodsFor this aggregate data meta-analysis, we searched MEDLINE, EMBASE and Scopus from 1st January, 1990, to 22 October, 2025, using terms for "tuberculosis", "microbial biomarker", and "human blood" to identify studies in which participants underwent blood sampling for detection of cell-free Mtb DNA, cell-associated Mtb DNA, protein/peptide Mtb antigens and lipid/glycolipid Mtb antigens before {+/-} after initiation of antimicrobial therapy. For bivariate analyses we used hierarchical summary receiver operating characteristic (HSROC) models to calculate areas under HSROC curves (AUC) for each analyte class to evaluate diagnostic accuracy for tuberculosis disease. For longitudinal analyses, we calculated risk differences to evaluate changes in proportions of biomarker-positive individuals after vs. before initiation of antimicrobial therapy, and pooled them using random-effects meta-analysis. Findings137 eligible articles were identified in the search, of which 109 vs. 13 contributed data to bivariate vs. longitudinal analyses, respectively. For cell-free Mtb DNA targets, AUC was 0.87 (95% CI 0.84 to 0.89), with sensitivity 61.5% (51.0 to 71.0) and specificity 93.0% (88.1 to 96.1); 4,878 samples from 34 unique study/setting/biomarker combinations (investigations). For cell-associated Mtb DNA targets, AUC was 0.93 (0.90 to 0.95), with sensitivity 43.9% (29.4 to 59.4) and specificity 97.1% (94.5 to 98.5); 3,589 samples, 32 investigations. For protein/peptide targets, AUC was 0.94 (0.92 to 0.96), with sensitivity 78.9% (73.2 to 83.6) and specificity 92.9% (90.7 to 94.5%); 10,260 samples, 61 investigations. For lipid/glycolipid targets, AUC was 0.96 (0.94 to 0.97), with sensitivity 68.6% (54.1 to 80.3) and specificity 97.0% (94.0 to 98.5); 3,287 samples, 22 investigations. Pooled risk differences for proportions of individuals biomarker-positive after vs. before initiation of antimicrobial therapy were -0.44 (-0.89 to 0.01; 68 samples, 5 investigations) for cell-free Mtb DNA; -0.46 (-0.88 to -0.03; 89 samples, 5 investigations) for cell-associated Mtb DNA, and -0.24 (-0.75 to 0.28; 160 samples, 4 investigations) for protein/peptide antigens. No studies investigating responses of lipid/glycolipid antigens to antimicrobial therapy were identified. Heterogeneity was moderate (I2 25-50%) for the majority of studies. 98/109 and 11/13 studies contributing data to bivariate vs. longitudinal analyses, respectively, were assessed as being at high risk of bias. InterpretationMolecular and biochemical microbial blood biomarkers exhibit similar accuracy for detection of tuberculosis disease, with specificity consistently exceeding sensitivity. Cell-associated Mtb DNA biomarkers exhibited a statistically significant response to antimicrobial therapy, with similar trends observed for cell-free Mtb DNA and protein/peptide antigens. These findings should be interpreted cautiously in the light of high risk of bias for many of the primary studies contributing data. Higher quality studies are needed to evaluate this emerging class of tuberculosis biomarkers. FundingBarts Charity, The Medical College of Saint Bartholomews Hospital Trust, Wellcome HARP Doctoral Fellowship Scheme. RESEARCH IN CONTEXT Evidence before this studyThe World Health Organisation (WHO) has identified high-priority biomarker needs for screening, diagnosis, evaluating likelihood of disease progression and treatment monitoring for tuberculosis. Numerous studies reporting utility of microbial blood biomarkers for diagnosis and treatment monitoring of M. tuberculosis (Mtb) infection and tuberculosis disease have been conducted, but up-to-date systematic reviews and meta-analyses of these data are lacking. We performed a systematic search of MEDLINE, EMBASE and Scopus from 1st January, 1990, to 22 October, 2025, using terms for "tuberculosis", "microbial biomarker", and "human blood" to identify studies in which participants underwent blood sampling for detection of cell-free Mtb DNA, cell-associated Mtb DNA, protein/peptide Mtb antigens and lipid/glycolipid Mtb antigens before {+/-} after initiation of antimicrobial therapy. Multiple studies have investigated utility of microbial blood biomarkers for detection of tuberculosis disease and monitoring responses to antimicrobial therapy, but only three relevant systematic reviews have been conducted to date, of which two (2007, 2021) report on detection of cell-free Mtb DNA, and one (2011) reports on antigen detection tests. Numerous primary studies have been published since these meta-analyses were conducted, but up-to-date syntheses incorporating the latest data for all classes of microbial blood biomarker for tuberculosis are lacking. Added value of this studyTo our knowledge, this study is the most comprehensive systematic review and meta-analysis of data from studies of microbial blood biomarkers of Mtb infection and tuberculosis disease conducted to date. It is also the first meta-analysis to synthesise data from studies investigating detection of cell-associated Mtb DNA in blood. Bivariate analysis of data from 109 studies revealed AUC values of 0.87 to 0.96 for the four microbial biomarker classes investigated, with sensitivity vs. specificity ranging from 43.9% to 80.2% vs. 87.9% to 97.1%, respectively. Cell-associated Mtb DNA biomarkers exhibited a statistically significant response to antimicrobial therapy, with similar trends observed for cell-free Mtb DNA and protein/peptide antigens. However, most primary studies were assessed as being at high risk of bias. Implications of all the available evidenceMolecular and biochemical microbial blood biomarkers exhibit similar accuracy for detection of tuberculosis disease, with specificity consistently exceeding sensitivity. Cell-associated Mtb DNA biomarkers exhibited a statistically significant response to antimicrobial therapy, with similar trends observed for cell-free Mtb DNA and protein/peptide antigens. These findings should be interpreted cautiously in the light of high risk of bias for many of the primary studies contributing data. Higher quality studies are needed to evaluate this emerging class of tuberculosis biomarkers.