Serum alkaline phosphatase may play a role in the differential diagnosis of sarcoidosis and tuberculosis

Background: Reaching the differential diagnosis of tuberculosis and sarcoidosis can be difficult due to granulomatous inflammation. The aim of this study was to determine alkaline phosphatase (ALP) activity in serum for the differential diagnosis of tuberculosis and sarcoidosis. Methods: This study comprised 242 subjects: 105 acid-fast bacilli (AFB) positive and/or culture-positive patients with pulmonary tuberculosis, 90 patients with biopsyproven sarcoidosis and a control group consisting of 47 healthy controls were included. ALP activity was measured in serum at the first admission of the patients. Results: The mean serum ALP was 112.74±55.14 IU/L in pulmonary tuberculosis, 76.14±34.23 IU/L in sarcoidosis, and 66.87±18.49 IU/L in the control group, respectively. There was a statistically significant difference between the patient population and the control group (P = 0.03). Also, there was a statistically significant difference between the tuberculosis and sarcoidosis groups (P = 0.034). According to the comparison of tuberculosis and sarcoidosis, the cut-off value was determined as 71.50 IU/L, which had sensitivity of 80%, specificity of 51%, PPV of 66%, NPV of 69%, accuracy of 67%, and the AUC was 0.728. Conclusion: ALP, as a little-known marker for tuberculosis and sarcoidosis, was significantly increased in the pulmonary tuberculosis group compared with the sarcoidosis group. As such, it may be a useful tool for the differentiation of tuberculosis and sarcoidosis.