Evaluating chronic kidney disease in rural South Africa: comparing estimated glomerular filtration rate using point-of-care creatinine to iohexol measured GFR

Objectives: The prevalence of chronic kidney disease is rising rapidly in low- and middle-income countries. Serum creatinine and estimation of glomerular filtration rate (GFR) are critical diagnostic tools, yet access to centralised laboratory services remains limited in primary care resource-limited settings. The aim of this study was to evaluate point-of-care (POC) technologies for serum creatinine measurement and to compare their performance to a gold standard measurement using iohexol measured GFR (mGFR). Methods: POC creatinine was measured using iSTAT (R) and StatSensor (R) devices in capillary and venous whole blood, and laboratory creatinine was measured using the compensated kinetic Jaffe method in 670 participants from a rural area in South Africa. GFR estimating equations Chronic Kidney Disease Epidemiology Collaboration and Modification of Diet in Renal Disease (CKD-EPI and MDRD) for POC and laboratory creatinine were compared to iohexol mGFR. Results: Calculated GFR for laboratory and POC creatinine measurements overestimated GFR (positive bias of 1.9-34.1 mL/min/1.73 m(2)). However, all POC devices had less positive bias than the laboratory Jaffe method (1.9-14.7 vs. 34.1 for MDRD, and 8.4-19.9 vs. 28.6 for CKD-EPI). Accuracy within 30% of mGFR ranged from 0.56 to 0.72 for POC devices and from 0.36 to 0.43 for the laboratory Jaffe method. POC devices showed wider imprecision with coefficients of variation ranging from 4.6 to 10.2% compared to 3.5% for the laboratory Jaffe method. Conclusions: POC estimated GFR (eGFR) showed improved performance over laboratory Jaffe eGFR, however POC devices suffered from imprecision and large bias. The laboratory Jaffe method performed poorly, highlighting the need for laboratories to move to enzymatic methods to measure creatinine.

Automated summary

The study evaluated the performance of point-of-care technologies for serum creatinine measurement compared to the gold standard measurement using iohexol measured GFR. Results showed that POC devices had better performance than the laboratory Jaffe method, but suffered from imprecision and significant bias. The study highlights the need for laboratories to transition to enzymatic methods for measuring creatinine.