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Abstract

Introduction

A new classification of chronic kidney disease (CKD) has been widely adopted that stratifies patients into 5 ‘stages’ according to estimated glomerular filtration rate (eGFR). In adults the most commonly used formulae to calculate eGFR are the Cockcroft and Gault (C&G) and Modification of Diet in Renal Disease (MDRD) formulae. The UK Renal Association has recommended calculation of MDRD eGFR to screen for reduced kidney function in primary and secondary care.

Aim

The aim of this study was to explore the implication of using these predictive formulae.

Methods

We searched for patients currently attending a renal clinic who have ever had a serum creatinine (SCr) of exactly 100 mol/L, 150 mol/L or 200 mol/L. The C&G and MDRD eGFRs corresponding to that SCr were calculated. The proportion of patients in each stage of the CKD classification was determined.

Results

For a SCr of 100 mol/L mean eGFR was 86.5ml/min (range 31.0 - 192.8) by C&G and 63.8ml/min (range 39.7 - 99.9) by MDRD (p<0.0001; t-test of mean). For SCr 150 mol/L mean eGFR was 51.7ml/min (18.0 - 110.4) by C&G and 38.0ml/min (20.7 - 54.8) by MDRD (p<0.0001). For SCr of 200 mol/L mean eGFR was 34.4ml/min (12.6 - 89.5) by C&G and 27.3ml/min (16.7 - 41.3) by MDRD (p<0.0001). Using MDRD eGFR 46.5% patients with a SCr of 100 mol/L have stage 3 CKD (GFR 30-60ml/min) and all patients with a SCr of 150 mol/L or 200 mol/L have CKD 3 or worse. 8.6% of males with SCr 100 mol/L had stage 3 CKD or worse compared with 86.8% females. 70.2% patients > 65 years old with SCr 100 mol/L had stage 3 CKD.

Conclusions

Targeted screening of patients at-risk for CKD will identify a large number of patients who require management of CKD and potential referral to nephrology services even at levels of SCr regarded as ‘normal’ or mildly elevated. This will apply especially to elderly patients and females.

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