Blood cell markers and acute phase reactants as a strategy to differentiate between pulmonary tuberculosis and community-acquired pneumonia: a retrospective cohort study

Objective: To determine the diagnostic yields of the different types of cell indices alone or in combination with C-reactive-protein(CRP) to distinguish between Pulmonary-tuberculosis(PT) and community-acquired-pneumonia(CAP). Methods: A retrospective cohort study was conducted in a high-complexity care center in Colombia, evaluating different types of cell indices in PT and CAP patients. A-receiver-operating-characteristic (ROC)-curve was plotted, and the area-under ROC-curve was calculated for each of these indices, as well as for CRP and procalcitonin values. Results: A total of 544 subjects were included in the final analysis. Of these, 270(49,6%) were diagnosed with PT and 274(50,4%) with CAP. Patients with CAP had significantly higher levels of leukocytes, neutrophils, monocytes, hemoglobin, hematocrit, and platelets than patients with PT (p < 0,05for-all-comparisons). Procalcitonin did not show significant differences between the groups (p=0,061). CRP has the highest ROC-curve for differentiating between PT and CAP, with ROC-curve of 0,76 (95%CI:0,71-0,88) and 0,75 (95%CI:0,71-0,80), respectively. Procalcitonin did not show discriminatory power for these two diseases, with an ROC-curve of 0,60 (95%CI:0,50-0,71). Conclusion: CRP and blood-cell-markers were the best markers to differentiate between patients with PT and CAP. The performance of these markers was acceptable, suggesting that they could be useful in clinical setting for suspected tuberculosis or CAP.