To the Editors:
The study by Ugajin et al. 1 nicely evaluates the role of procalcitonin in differentiating community-acquired pneumonia (CAP) from pulmonary tuberculosis (PTB). They have further highlighted its prognostic value in PTB. Few aspects regarding this promising biomarker need to be discussed to understand its clinical significance.
Procalcitonin, a propeptide of calcitonin, is an important host response biomarker indicative of infection. In particular, it aids in assessing the severity of infection and its prognosis 2, 3. Using this severity marker to differentiate two infectious diseases seems unjustified. Both the diseases can have varying degrees of severity and may also be confounded by factors such as immunocompromised status and presence of comorbidities, such as post surgery 4, trauma 5, acute exacerbations of chronic obstructive pulmonary disease and acute coronary syndrome, which can alter procalcitonin levels. Clinical presentations, pattern of radiological involvement and sputum examination still remain the gold standard, as well as cost-effective measures to differentiate PTB and CAP.
Serum procalcitonin, although an important prognostic marker, may not be useful in the presence of the aforementioned comorbidities. Extensive radiological involvement, multiorgan infection, high sputum positivity and drug resistance are more reliable markers for severity of tuberculosis and poor prognosis. Serum procalcitonin measurement should be performed in selected cases of PTB where its positivity should alert the clinician to search for tubercular foci in other organs of the body.
Footnotes
Statement of Interest
None declared.
- ©ERS 2011