Application of a point of care creatinine device for trend monitoring in kidney transplant patients: fit for purpose?

Abstract

Background: The StatSensor (R) Xpress-i (TM), a point-of-care system for blood creatinine measurement, offers patients the possibility of self-monitoring creatinine. In this study, the analytical performance of the StatSensor (R) for both detecting current renal function and monitoring renal (dys) function in kidney transplant patients was examined. Methods: Accuracy of the StatSensor (R) with capillary and venous whole blood was evaluated and compared to an isotopic dilution mass spectrometry (IDMS)-traceable enzymatic creatinine test in venous serum (n = 138). Twenty Li-heparin samples were compared to the IDMS reference method performed by a Joint Committee for Traceability in Laboratory Medicine (JCTLM)-listed reference laboratory (RfB, Bonn, Germany). To evaluate StatSensor (R)'s suitability to monitor kidney function, both venous and capillary samples were obtained in 20 hospitalized transplantation patients. Venous samples were analyzed with an IDMS-traceable enzymatic test, capillary samples were measured using the StatSensor (R). For all 2-day intervals, percentage change in creatinine was compared between both methods. Results: The StatSensor (R) did not meet total allowable error criterion of 6.9%. Average overall CV a for the StatSensor (R) was 10.4% and 5.2% for capillary and venous whole blood results, respectively. Overall CV a for the central laboratory serum creatinine method was <1.5%. For monitoring renal (dys) function, total agreement of the StatSensor (R) with an IDMS-traceable enzymatic test was 68% using a 10%. change. No significant differences were found between the changes observed by both methods. Conclusions: Capillary blood testing with the StatSensor (R) is not advisable for determining current renal function with a single creatinine measurement in kidney transplant patients, mainly due to excessive analytical imprecision. However, our results suggest that capillary blood testing with the StatSensor (R) can be used for daily trend monitoring of kidney function after renal transplantation.