Procalcitonin kinetics and nosocomial pneumonia in older patients.

BACKGROUND Early identification of treatment failure for nosocomial pneumonia remains a major challenge. The goal of this study was to test whether procalcitonin kinetics can be used to assess the clinical efficacy in older critically ill patients with nosocomial pneumonia. METHODS A prospective observational study was conducted with 60 subjects (≥ 65 y old) admitted to the ICU with severe nosocomial pneumonia. Serum procalcitonin was measured on days 0, 3, and 7 and at the end of treatment. The procalcitonin time course was analyzed according to the therapeutic efficacy. RESULTS Procalcitonin levels were elevated in all subjects (n = 60) on day 0, and the median level (range) was 2.5 (0.8-42.7) μg/L. There were no differences in procalcitonin between the improved subjects (n = 41) and those without improvement (n = 19) on day 0 (P > .05). However, lower procalcitonin levels on days 3 and 7 and at the end of treatment (all P < .05) and greater rates of procalcitonin decline between days 0 and 3 (ΔPCT(d3)%; 29.5 ± 10.8% vs 15.1 ± 5.9%, P = .009) were observed in the improved subjects compared with those with no improvement. ΔPCT(d3)% was the best single predictor of efficacy (area under the curve of 0.79, P < .001) and had a sensitivity of 75.7% and a specificity of 72.0% with a threshold of 26.2%. By comparison, traditional parameters and absolute procalcitonin failed to predict treatment response (P > .05). Indeed, the combination of ΔPCT(d3)% > 26.2% and a modified Clinical Pulmonary Infection Score of < 6 points improved the predictive value (area under the curve of 0.89, sensitivity of 81.3%, specificity of 86.5%). CONCLUSIONS Procalcitonin levels were not influenced by aging, and procalcitonin kinetics might help to identify treatment failure. ΔPCT(d3)% in combination with the Clinical Pulmonary Infection Score has been shown to be a marker of clinical efficacy at an earlier stage.