COMPARISON OF BIOMARKERS OF PULMONARY TUBERCULOSIS ACTIVITY: Serum Surfactant Proteins A and D, KL-6, C-Reactive Protein, and Erythrocyte Sedimentation Rate

[Objective] To evaluate serum surfactant proteins A and D (SP-A and SP-D), KL-6, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) as biomarkers for monitoring the activity of pulmonary tuberculosis. [Methods] Patients with recently diagnosed and sputum smear-positive pulmonary tuberculosis were consecutively recruited between February and April 2013 at the Kanagawa Cardiovascular and Respiratory Center. Serum levels of SP-A, SP-D, KL-6, and CRP, and ESR were measured twice before treatment initiation and after confirmation of disease improvement (indicated by two consecutive negative smears or one negative sputum culture). The relationship of those biomarkers with disease activity was evaluated by comparing the baseline values with the biological and radiological disease severities and by assessing the changes in those values before and after treatment. [Results] Twenty-seven patients with pulmonary tuberculosis were enrolled in the study. The median age was 66 years, and the male/female ratio was 19/8 for the entire cohort. The baseline levels of most biomarkers significantly or relatively increased in patients with severe biological and radiological outcomes, which were indicated by findings such as long-term positive sputum culture, and the presence of cavities and shadows on chest radiographs. A second measurement of these biomarkers was performed after a median treatment period of 56 days. The changes in the median levels for these biomarkers were as follows (before/after treatment): SP-A (ng/mL), 55.3/39.2 (p＜0.01); SP-D (ng/mL), 71.5/38.5 (p＝0.03); KL-6 (U/mL), 365/374 (p＝0.43); CRP (mg/dL), 3.8/0.4 (p＜0.01); ESR (mm/hr), 69/46 (p＝0.27). After treatment, the levels of SP-A, SP-D, and CRP significantly decreased. [Conclusion] The levels of SP-A, SP-D, and CRP reflected not only the baseline values but also the chronological disease activity. Therefore, these biomarkers could be useful for the management of pulmonary tuberculosis.