Evaluation of a point-of-care serum creatinine measurement device and the impact on diagnosis of acute kidney injury in pediatric cardiac patients: A retrospective, single center study

Background and aims: Agreement between measurements of creatinine concentrations using point-of-care (POC) devices and measurements conducted in a standard central laboratory is unclear for pediatric patients. Our objectives were (a) to assess the agreement for pediatric patients and (b) to compare the incidence of postoperative acute kidney injury (AKI) according to the two methods. Methods: This retrospective, single-center study included patients under 18 years of age who underwent cardiac surgery and who were admitted into the pediatric intensive care unit of a tertiary teaching hospital (Okayama University Hospital, Japan) from 2013 to 2017. The primary objective was to assess the correlation and the agreement between measurements of creatinine concentrations by a Radiometer blood gas analyzer (Cre_gas) and those conducted in a central laboratory (Cre_lab). The secondary objective was to compare the incidence of postoperative AKI between the two methods based on Kidney Disease Improving Global Outcomes (KDIGO) criteria. Results: We analyzed the results of 1404 paired creatinine measurements from 498 patients, whose median age was 14 months old (interquartile range [IQR] 3, 49). The Pearson correlation coefficient of Cre_gas vs Cre_lab was 0.968 (95% confidence interval [CI], 0.965-0.972, P < 0.001). The median bias between Cre_gas and Cre_lab was 0.02 (IQR -0.02, 0.05) mg/dL. While 199 patients (40.0%) were diagnosed as having postoperative AKI based on Cre_lab, 357 patients (71.7%) were diagnosed as having postoperative AKI based on Cre_gas (Kappa = 0.39, 95% CI, 0.33-0.46). In a subgroup analysis of patients whose Cre_gas and Cre_lab were measured within 1 hour, similar percentage of patients were diagnosed as having postoperative AKI based on Cre_gas and Cre_lab (42.8% vs 46.0%; Kappa = 0.76, 95% CI, 0.68-0.84). Conclusion: There was an excellent correlation between Cre_gas and Cre_lab in pediatric patients. Although more patients were diagnosed as having postoperative AKI based on Cre_gas than based on Cre_lab, paired measurements with a short time gap showed good agreement on AKI diagnosis.