Automated reporting of eGFR: a useful tool for identifying and managing kidney disease

The use of absolute values improves performance of estimation formulae: a retrospective cross sectional study

BACKGROUND

Estimation of Glomerular Filtration Rate (GFR) by equations such as Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) or Modification of Diet in Renal Disease (MDRD) is usually expressed as a Body Surface Area (BSA) indexed value (ml/min per 1.73 m²). This can have severe clinical consequences in patients with extreme body sizes, resulting in an underestimation in the case of obesity or an overestimation of GFR in the case of underweight patients. The aim of this study was to compare the performance of both estimation formula expressed in ml/min, instead of ml/min per 1.73 m², with a reference method.

METHODS

Retrospective single centre cross sectional study of 185 patients. GFR was measured with 51Cr-EDTA and estimated with CKD-EPI and MDRD. Bias, precision and accuracy of absolute estimated GFR was calculated.

RESULTS

Bias of CKD-EPI and MDRD formulae expressed as an absolute value was 0.49 and 0.27 ml/min respectively, which is lower than previously reported. Precision was 12.95 and 16.33 and accuracy expressed as P30 was over 92.43% for CKD-EPI. There were no significant differences in GFR between the reference method and the estimation formulae.

CONCLUSIONS

The performance of CKD-EPI and MDRD formulae can be significantly improved in the individual patient if the absolute values are used by removing the BSA normalization factor. Absolute estimated GFR by CKD-EPI is comparable to measured GFR, improving the performance of this formula in the assessment of individual kidney function, thus providing clinicians with an alternative to reference methods.

Reporting of the estimated glomerular filtration rate decreased creatinine clearance testing

The Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines suggest that clinicians use the estimated glomerular filtration rate (eGFR) measurements and minimize the use of timed urine creatinine clearance collection. The intent of this change was to improve recognition of chronic kidney disease. Here we used time-series modeling and intervention analyses to determine the effect of publication of the K/DOQI guidelines and the introduction of widespread eGFR reporting with prompts on physician ordering of 24-h urine collection for creatinine clearance. In this setting, clinical practice guidelines did not influence creatinine clearance testing; however, the direct introduction of eGFR reporting with prompts into physician workflow resulted in a sudden and significant 23.5% decrease in creatinine clearance collection over the 43 months analyzed. Thus, eGFR reporting with prompts may have produced a clinical practice change because it is integrated directly into physician workflow. Changing physician practice patterns may require more than publishing guidelines; rather it is more likely to occur through educational and structural changes to practice.