Accuracy of freely available online GFR calculators using the CKD-EPI equation

PURPOSE: Estimated glomerular filtration rate (eGFR) as calculated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is used for detection of chronic kidney disease and drug dose adjustment. The purpose of the present study was to investigate the accuracy of freely available eGFR online calculators. METHODS: All identified CKD-EPI online calculators were run with five reference cases differing in age, sex, serum creatinine, and ethnicity. Conversion from eGFR(indexed) (unit ml/min per 1.73 m(2)) to eGFR(non-indexed) (unit ml/min) and creatinine unit from milligramme/decilitre to micromole/litre was checked, if available. RESULTS: Only 36 of 47 calculators (76.6%) produced accurate eGFR results for all reference cases. Eight of 47 (17.0%) calculators were considered as faulty because of errors relating to ethnicity (4 calculators), to conversion of the eGFR unit (2 calculators), to erroneous eGFR values without obvious explanation (2 calculators), to conversion of the creatinine unit (1 calculator), and to an error in the eGFR unit displayed (1 calculator). Overall, 28 errors were found (range 59 to 147% of the correct eGFR value), the majority concerning calculation of eGFR(indexed) and the conversion to eGFR(non-indexed). Only 7 of 47 (14.9%) calculators offered conversion of the eGFR unit. CONCLUSIONS: Erroneous calculations that might lead to inappropriate clinical decision-making were found in 8 of 47 calculators. Thus, online calculators should be evaluated more thoroughly after implementation. Conversion of eGFR units that might be needed for drug dose adjustments should be implemented more often. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00228-020-02932-x) contains supplementary material, which is available to authorized users.