Serum procalcitonin as a biomarker of bloodstream infection & focal bacterial infection in febrile patients.

Background & objectives: Bacteraemia is a serious form of infection in patients presenting with fever, thus, there is a necessity for a biomarker for rapid diagnosis of bacteraemia in such patients to make better therapeutic decisions. This study was conducted to measure the serum procalcitonin (PCT) levels at the time of initial presentation as a biomarker for identifying bacteraemia and as a predictor of mortality in patients admitted with acute fever. Methods: Four hundred and eighty patients, who presented with acute fever requiring admission to a tertiary care teaching hospital in south India, were prospectively studied. All patients were evaluated with a detailed history, physical examination, laboratory and imaging studies. Baseline serum PCT was measured for each patient within six hours of admission. Results: Among patients with single infectious cause (n=275), significantly higher median serum PCT levels were evident in bacteraemia compared to leptospirosis (P=0.002), dengue (P <0.001), scrub typhus (P <0.001) and evident focus of infection without bacteraemia (P=0.036). By receiver-operator characteristic curve analysis, at a cut-off value of >3.2 ng/ml, the sensitivity and specificity of serum PCT levels in predicting bacteraemia were 81.1 and 63.3 per cent, respectively. As per the worst-case scenario analysis, 91 (18.9%) patients had a poor outcome and these had significantly higher median serum PCT levels compared to survivors (n=389) [9.46 (2.03-44.4) vs. 1.23 (0.34-7.645); P <0.001]. At a cut-off value of >3.74 ng/ml, serum PCT levels at initial presentation predicted in-hospital mortality with a sensitivity and specificity of 67 and 67.5 per cent, respectively. Interpretation & conclusions: Our observations suggest that serum PCT level may be a useful biomarker for identifying bacteraemia as well as predicting mortality in patients with acute fever requiring admission to hospital.