Abstract
PurposeEstimated 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.MethodsAll identified CKD-EPI online calculators were run with five reference cases differing in age, sex, serum creatinine, and ethnicity. Conversion from eGFRindexed (unit ml/min per 1.73 m2) to eGFRnon-indexed (unit ml/min) and creatinine unit from milligramme/decilitre to micromole/litre was checked, if available.ResultsOnly 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 eGFRindexed and the conversion to eGFRnon-indexed. Only 7 of 47 (14.9%) calculators offered conversion of the eGFR unit.ConclusionsErroneous 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.
Highlights
In clinical routine, glomerular filtration rate (GFR) is most commonly estimated with the creatinine-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.The creatinine-based chronic kidney disease (CKD)-EPI equation requires age, sex, ethnicity, and a standardised measurement of serum creatinine [2]
The CKD-EPI equation provides a GFR estimate with the unit millilitre/minute per 1.73 m2, i.e. an estimate normalised to a body surface area (BSA) of 1.73 m2, which appears appropriate for detection and staging of CKD [1]
In a recent analysis, eGFRnon-indexed calculated with the CKD-EPI equation performed best at predicting dose requirements for carboplatin, closely followed by eGFRnonindexed calculated with the MDRD equation [18]
Summary
The creatinine-based CKD-EPI equation requires age, sex, ethnicity, and a standardised measurement of serum creatinine [2]. In case of drug dose adjustment, a non-normalised individual estimate with units of millilitre/minute is desired, especially if a patient’s BSA differs significantly from 1.73 m2. In such cases, the estimate should be individualised according to a patient’s BSA (eGFRnon-indexed = eGFRindexed / 1.73 · BSA) [1, 11, 13,14,15,16,17]. EGFRnon-indexed calculated with CKD-EPI or MDRD equation was more accurate than eGFRindexed compared with measured 51Cr-EDTA or 99mTc-DTPA GFR [19, 20]
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