Modified end-stage renal disease risk score for Chinese type 2 diabetic patients—the Hong Kong Diabetes Registry

To the Editor: Ma et al. [1] recalibrated the Modification of Diet in Renal Disease (MDRD) equation for estimation of the GFR of Chinese individuals. It was reported that it is necessary for the GFR derived from the original MDRD equation to be multiplied by an adjusting coefficient of 1.233. This recalibration for Chinese individuals may have a significant effect on the end-stage renal disease (ESRD) risk score [2]. If a GFR of 15 ml min 1.73 m is used to define ESRD, patients with values between 12.17 and 15.00 ml min 1.73 m estimated by the original MDRD equation will no longer meet the definition of ESRD by the Chinese recalibrated MDRD (C-MDRD) equation. The aim of the present study was to examine the effect of the C-MDRD equation on the validity of the ESRD risk score for Chinese patients with type 2 diabetes mellitus [2]. The study population, clinical measurements, definition of ESRD and laboratory assays have been described previously [2]. Due to the reduced number of patients with ESRD following application of the C-MDRD equation, the updated database of the Hong Kong Diabetes Registry, which contains 4,799 previously recruited patients [2] and 3,121 patients not previously reported, was used to examine the impact of the CMDRD equation on the ESRD risk score. The C-MDRD [1] used to estimate GFR in ml min 1.73 m was: GFR=186× (SCR×0.011) × (age) × (0.742 if female) × 1.233, where SCR is serum creatinine expressed as μmol/l (original mg/dl converted into μmol/l) and 1.233 is the adjusting coefficient. As previously described, ESRD was defined as: (1) death due to diabetes with renal manifestations or renal failure (the International Classification of Diseases, 9th Revision [ICD-9] code 250.4, 585, 586); (2) hospitalisation due to non-fatal renal failure (ICD-9 codes 585 or 586); (3) GFR<15 ml min 1.73 m [2]. Follow-up time was calculated as the period from enrolment up to either the date of occurrence of any one of the above events during followup or 30 July 2005, whichever came first. Of 7,920 patients, 7,516 type 2 diabetic patients who did not have ESRD (GFR≥15 ml min 1.73 m or hospitalisation due to renal failure) at enrolment were analysed in the study. A total of 40,171.6 person-years were observed. At enrolment, 10.2% (n=765) of the 7, 516 patients had a GFR of between 15 and 60 ml min 1.73 m, and 15.54% (n= 1,168) had a spot urinary albumin:creatinine ratio (ACR) of ≥30 mg/mmol. Three hundred forty-nine patients developed Diabetologia (2007) 50:1348–1350 DOI 10.1007/s00125-007-0639-7