Negative predictive value of serum-Procalcitonin (PCT) for active tuberculosis

Background: Procalcitonin (PCT) is a precursor peptide for calcitonin. Beside thyroid tissue the most important sources for PCT are lung and liver parenchyma, kidney tissue and skeletal muscles. While PCT is released by neutrophils it proved to be an excellent marker for bacterial pulmonary infections. In patients with inflammatory pulmonary infiltrates mycobacterial infection should always be considered as one of the differential diagnosis. As defence mechanisms against mycobacteria are lymphocyte driven elevated serum levels of procalcitonin may not to be expected.

Hypothesis: PCT levels are significantly lower in patients with active pulmonary tuberculosis compared to patients with other bacterial pulmonary infections.

Methods: Prospective case control study of all individuals admitted with suspected pulmonary tuberculosis at a single center. Measurement of PCT serum levels on the day of admission.

Results: At the time of submission of the abstract 31 individuals were enrolled. Fifteen patients were diagnosed with pulmonary TB by cultural proof of Mycobacterium tuberculosis from bronchopulmonary specimen, 16 patients were diagnosed with diseases different from pulmonary tuberculosis, including community acquired pneumonia, idiopathic fibrosis and malignancies. Except for two patients suffering from miliary tuberculosis revealing PCT serum levels between 0,3 and 0,4ng/ml the PCT serum levels of the other 13 tuberculosis patients with tuberculosis were <0,1ng/ml including two patients with tuberculous pleural effusion.

Results: Serum Procalcitonin does not seem to be elevated in cases of active tuberculosis and may be a usefull additional marker for the rapid exclusion of tuberculosis from pneumonias of other bacterial origin.