An improved algorithm for rapid diagnosis of pleural tuberculosis from pleural effusion by combined testing with GeneXpert MTB/RIF and an anti-LAM antibody-based assay

BACKGROUND: This retrospective study evaluated the performance of a lipoarabinomannan (LAM)-based immunological method for diagnosing pleural tuberculosis (TB) from pleural effusion samples. Results were compared to those obtained using conventional culture and molecular testing methods. METHODS: Suspected pleural TB patients who visited Beijing Chest Hospital for medical care between January 2016 and June 2017 were retrospectively analysed in the study. Pleural effusion samples were tested for Mycobacterium tuberculosis (MTB) using the BACTEC MGIT 960 System, GeneXpert, and an anti-LAM antibody assay (LAM assay). RESULTS: Pleural effusion samples were collected from a total of 219 retrospectively recruited participants suspected of having pleural TB. Thirteen of 155 confirmed pleural TB cases tested positive for MTB via MGIT culture, for a sensitivity of 8.4% [95% confidence interval (CI): 4.0–12.8%]. In addition, GeneXpert and LAM testing identified 22 and 55 pleural TB cases, for sensitivities of 14.2% (95% CI: 8.7–19.7%) and 35.5% (95% CI: 28.1–43.6%), respectively. The specificities of these two assays were 100.0% (95% CI: 92.9–100.0%) and 96.9% (95% CI: 88.2–99.5%), respectively. Combined application of culture and LAM testing identified 60 positive cases, for a sensitivity of 38.7% (95% CI: 31.0–46.4%) that was significantly higher than that of MGIT culture alone (P < 0.01). Similarly, use of LAM testing in combination with GeneXpert led to correct diagnosis of 40.0% (95% CI: 32.3–47.7%) of pleural TB cases, a higher rate than obtained using GeneXpert alone (P < 0.01). In addition, the specificity of the combined assay of GeneXpert and LAM testing was 96.9% (95% CI: 88.2–99.5%). Patients aged 25 to 44 years were more likely to have positive LAM assay results than those ≥65 years of age (P = 0.02). Meanwhile, the proportion of diabetic patients with positive LAM assay results was significantly lower than that of the non-diabetes group (P = 0.03). CONCLUSIONS: An anti-LAM antibody detection assay showed potential for diagnosis of pleural TB from pleural effusion samples. Combined use of the LAM assay with MGIT culture or GeneXpert methods could improve sensitivity for improved pleural TB diagnosis compared to results of individual conventional tests alone.