Can procalcitonin measurement help in differentiating between bacterial infection and other kinds of inflammatory processes?

OBJECTIVE: To study the levels of procalcitonin (PCT) in various inflammatory states seen in an internal medicine department and to evaluate the possible discriminative role of PCT in differentiating bacterial infection from other inflammatory processes.

METHODS: PCT, C reactive protein (CRP), and white blood cell count (WBC) were measured in patients admitted to the department for fever or biological inflammatory syndrome, or both. The serum of 173 consecutive patients was analysed according to the aetiological diagnosis. The patients were divided into two groups: group I (n=60) with documented bacterial or fungal infection; group II (n=113) with abacterial inflammatory disease.

RESULTS: PCT levels were >0.5 ng/ml in 39/60 (65%) patients in group I. In group II, three patients with a viral infection had slightly increased PCT levels (0.7, 0.8, and 1.1 ng/ml) as did two others, one with crystal arthritis and the other with vasculitis (0.7 ng/ml in both cases). All other patients in group II had PCT levels <0.5 ng/ml. In this study a value of PCT >0.5 ng/ml was taken as the marker of bacterial infection (sensitivity 65%, specificity 96%). PCT values were more discriminative than WBC and CRP in distinguishing a bacterial infection from another inflammatory process.

CONCLUSION: PCT levels only rose significantly during bacterial infections. In this study PCT levels >1.2 ng/ml were always evidence of bacterial infection and the cue for starting antibiotic treatment.