Procalcitonin Fails to Differentiate Inflammatory Status or Predict Long-Term Outcomes in Peritoneal Dialysis-Associated Peritonitis
Authors: Lam Man Fai , Leung Joseph C.K. , Lam Christopher W.K. , Tse Kai Chung , Lo Wai Kei , Lui Sing Leung , Chan Tak Mao , Tam Sidney , Lai Kar Neng 
Published: February 2020

Background Peritonitis is the major complication in patients undergoing maintenance peritoneal dialysis (PD) and is associated with a significant risk of mortality. Previously, we have shown that patients treated for peritonitis and having prolonged elevation of C-reactive protein (CRP) are associated with higher mortality. The underlying cause for the chronic systemic inflammation remains unknown. We studied serum procalcitonin (PCT), which has been reported as an accurate marker for infection and inflammation, with respect to being a diagnostic and prognostic indicator of persistent chronic inflammation after peritonitis in patients with PD-related peritonitis. Methods We conducted a prospective study on PD patients that developed PD-related peritonitis. Blood samples obtained at routine check-up before the onset of peritonitis were taken as baseline (D0). When patients developed PD-related peritonitis, serial blood samples were obtained on day 1 (D1), day 7 (D7), and day 42 (D42) for PCT, CRP, and other inflammatory markers. Patients were followed up for at least 2 years, during which outcomes of peritonitis and causes of death were recorded. Serum levels of CRP and PCT at day 42 were analyzed to assess for long-term prognosis. Results 35 patients [female 42.9%; mean age 63.8 ± 13.1 years; 12 (34.3%) diabetics] were recruited. The onset of peritonitis was 3.61 ± 3.56 years after PD initiation and median residual renal function at that time was 1.06 (range 0 – 6.1) mL/min. Median total white cell counts in PD effluent at days 1, 3, 7, and 42 were 3505/mm3 (range 377 – 20500/mm3), 297 (8 – 5880)/mm3, 34 (0 – 5290)/mm3, and 10 (0 – 115)/mm3, respectively. Twelve (34.3%) and 14 (40%) PD effluents grew gram-positive and gram-negative micro-organisms respectively; others were culture negative. Median PCT was increased significantly at day 1 [2.00 (0.12 – 58.7) ng/mL, p < 0.001], day 7 [0.76 (0.13 – 15.25) ng/mL, p < 0.001], and day 42 [0.30 (0.13 – 0.79) ng/mL, p = 0.005] compared to baseline [0.20 (0.09 – 0.69) ng/mL]. Seven of 35 patients had false-negative results on day 1 (range 0.12 – 0.46) when PCT <0.5 ng/mL was used as the cutoff value for diagnosing peritonitis. For the long-term prognostic outcome, CRP at day 42 was significantly better than PCT in assessing overall prognosis (CRP: AUC 0.712, 95% CI 0.534 – 0.890 vs PCT: AUC 0.652, 95% CI 0.448 – 0.855). In Kaplan–Meier survival analysis, patients with elevated CRP (>3.0 mg/L) were associated with poorer long-term survival ( p = 0.04) but elevated PCT at the 25th, 50th, or 75th percentiles failed to provide prognostic value. Conclusions PD patients after peritonitis may be associated with prolonged systemic inflammation. CRP was a better serum marker for monitoring inflammatory status and predicting long-term prognosis in our study. Although serum PCT is elevated in some patients at the time of peritonitis, its value in making a diagnosis and predicting long-term prognosis remains doubtful.