Predictors of peritoneal dialysis associated peritonitis; application of the zero-inflated negative binomial model

Abstract

Introduction: Peritonitis is the main cause of morbidity and dropout from peritoneal dialysis (PD) program. Objectives: We aimed to determine risk factors predisposing to PD-associated peritonitis. Patients and Methods: As a retrospective cohort research, on 235 PD individuals with 4277 patientmonths of follow up, 170 episodes of peritonitis was reported in 93 patients. Data were extracted from medical records using a template. Standard as well as zero-inflated negative binominal regression was used to model the association between patients’ characteristics and the peritonitis rate. Cox-proportional hazard (PH) adjusted model was used to determine the effect of factors on the peritonitis-free survival. Results: With a mean (SD) body mass index (BMI) of 18.7(3.4) kg/m2, 109 (46.4%) of them were male. With a median (95% CI) follow-up time of 19 (16 to 36) months, the rate of peritonitis was 0.48 episode per patient-year. The most common micro-organism detected was coagulase-negative staphylococci (n=54; 31.7%). The only variable which was associated with a higher rate of peritonitis was BMI (rate ratio [RR]: 1.07; 95% CI 1.01 to 1.14; P value=0.031). Comparing to patients with lower education, patients with higher than elementary school of education had higher peritonitisfree survival (with hazard ratio [HR]=0.51; 95%CI 0.33-0.79, P value=0.003) and higher chance of having no peritonitis [odds ratio (OR):1.97; 95% CI 1.08 to 3.59; P value=0.029]. Conclusion: Peritonitis is still a major concern in PD patients. BMI was a risk factor for higher peritonitis rate. Higher education level was associated with lower peritonitis-free survival and higher chance of having no peritonitis.