Diagnostic and Prognostic Value of Procalcitonin in Tuberculosis Patients

Aims: Procalcitonin, the prohormone precursor of calcitonin rises in serum response to bacterial infections. Circulating PCT levels decrease when the infection is controlled by the host immune system or antibiotic therapy. The present study was conducted to measure the diagnostic and prognostic utility of procalcitonin in tuberculosis.
Methodology: The study group consisted of forty patients with pulmonary tuberculosis (PTB) and forty normal controls (NC). Blood was collected from NC and PTB (labeled as PTB-0). Patients underwent the 4-drug chemotherapy for 2 months following which blood was collected again (labeled as PTB-2). They were continued into the next 4 months of the 2-drug regimen. Blood was collected thereafter and labeled as PTB-6. All blood samples were semiquantitatively analyzed for procalcitonin.
Results: Serum PCT was < 0.5 ng/ml in thirty seven out of forty normal controls and > 2 ng/ml in three. The prohormone level was > 2ng/ml in fifteen and > 10 ng/ml in the rest of the PTB-0 subjects, thus indicating that PCT levels served as a useful marker of infection in PTB patients at diagnosis. After 2 months of intensive treatment the number of patients with PCT levels > 10 ng/ml increased to thirty two in PTB-2. Only 8 patients recorded plasma PCT levels > 2 ng/ml. At the end of 6 months of treatment, PCT values in all patients had decreased to < 2 ng/ml.
Conclusion: Serum PCT seemed to show diagnostic and prognostic utility at the end of treatment however, PCT is not specific for tuberculosis alone and may be raised in other lung infections. Future studies with quantitative analysis of PCT in tuberculosis in comparison to other lung infections are needed for better understanding of the role of PCT in PTB.