Platelet–lymphocyte ratios: a potential marker for pulmonary tuberculosis diagnosis in COPD patients

BACKGROUND: In recent decades, morbidity and mortality have been found to be significantly increased in patients with chronic obstructive pulmonary disease (COPD) complicated with pulmonary tuberculosis (PTB). Platelet–lymphocyte ratio (PLR) is an indicator for inflammatory diseases. This study aims to investigate whether PLR could act as a potential marker for patients with COPD complicated with PTB. METHODS: In this retrospective study, laboratory characteristics of 87 COPD patients complicated with PTB (determined by Mycobacterium tuberculosis positive culture from sputum or bronchial lavage fluid) and 83 COPD patients (as the control group, determined by M. tuberculosis culture negativity from sputum or bronchial lavage fluid) were investigated. Data obtained on the day of admission were analyzed. RESULTS: PLR >216.82 was identified as the optimal cutoff value for discriminating COPD patients with PTB (sensitivity 92.4%, specificity 84.5%, positive-predictive value 91.6%, negative-predictive value 86.2%, and area under the curve [AUC] was 0.87) from patients with COPD alone. The AUC of PLR was significantly greater than that of neutrophil–lymphocyte count ratio (AUC, 0.74; 95% confidence interval, 0.67–0.81; P<0.01). CONCLUSION: PLR could be developed as a valuable maker for identifying tuberculosis infection in COPD patients.