PURPOSE: Procalcitonin, is a protein known to rise in response to sepsis due to bacterial infections and to a lesser degree due to mycobacterial infections. In this study we examine the utility of serum procalcitonin in patients suspected to have pulmonary tuberculosis.
METHODS: This prospective study took place in a community hospital over a 12 month period. Thirty two patients were enrolled after being admitted to respiratory isolation with suspicion of pulmonary tuberculosis. Serum procalcitonin levels were tested on routine blood work drawn within the 24 hours of admission using the rapid procalcitonin test. Results were recorded as low when less than 0.5ng/ml and high when greater than or equal to 0.5ng/ml. The cultures of all patients were followed until all mycobacterial cultures were final.
RESULTS: The mean age of our patients was 60 years and their gender was divided equally. The median number of symptoms and risk factors for pulmonary tuberculosis was 5 and the median pneumonia severity index was 2. Seventeen patients were diagnosed with mycobacterial infections; eleven due to Mycobacterium tuberculosis and six due to Mycobacterium avium complex. The remaining 15 patients were diagnosed with bacterial (n:12) and fungal pneumonias (n:3). There was a statistically significant higher rate (p=0.0019) of high procalcitonin levels in the non-mycobacterial group (7/15) versus its mycobacterial counterpart (0/17). This rapid procalcitonin test was found to be 100% sensitive but 47% specific for diagnosing mycobacterial disease in this patient population.
CONCLUSION: The rapid procalcitonin test is most useful when used to rule out the disease since it has a high negative predicted value (100%) but a lower positive predicted value (68%). When excluding the easy to diagnose acid fast bacillus smear positive patients, the sensitivity and specificity of the rapid procalcitonin test did not change.
CLINICAL IMPLICATIONS: The smear negative culture positive tuberculosis patients are often difficult to identify. The rapid procalcitonin test can help us in the early diagnosis of pulmonary tuberculosis in our effort towards disease eradication.
DISCLOSURE: Theodore Patsis, No Financial Disclosure Information; No Product/Research Disclosure Information