S56 Serum procalcitonin for diagnosing and monitoring response in pleural infection

Aim To assess the value of procalcitonin in the diagnosis of pleural infection and its utility for monitoring response to treatment. Methods All patients presenting to our unit from September 2016 onwards with pleural infection had serum procalcitonin as well as CRP measured. Data were collected prospectively for all patients presenting with a clinical features of pleural infection (including fever and elevated blood inflammatory markers) and either acidic pleural fluid (pH Results 44 patients presented to our unit with pleural infection in the 22 months from September 2016. Figure 1 displays inflammatory marker trends during the first week. Procalcitonin appeared to be less sensitive than CRP in diagnosing pleural infection, particularly in patients with chronic symptoms (more than three weeks duration). CRP was elevated in all cases whilst procalcitonin was raised in 31 out of 34 patients with acute infection and in 5 of 10 patients with chronic infection. In patients with elevated procalcitonin, levels appeared to drop consistently in response to appropriate treatment and matched the patients’ reported wellbeing. In contrast, CRP did not show a consistent decline in all patients (Graph A and B). In a subgroup of the seven most challenging patients (Graph C and D) with features suggestive of persisting sepsis, namely swinging fever and persistently elevated CRP, procalcitonin trends indicated a steady improvement in systemic bacterial infection. Procalcitonin levels unexpectedly rose in two patients suggesting uncontrolled systemic bacterial infection. In one of these patients a resistant organism was isolated and in the other a new pleural collection had developed. Conclusion Procalcitonin is not as sensitive a marker of initial pleural infection as CRP. However, in patients with pleural infection, conventional markers of sepsis (fever and CRP) may be confounded by pleural inflammation. Procalcitonin appears to be a more specific marker of response to treatment and seems to correspond to the patient’s subjective wellbeing. Further studies are required to confirm this.