Predictive performance of eGFR equations in South Africans of African and Indian ancestry compared with 99mTc-DTPA imaging

Background

South African guidelines for early detection and management of chronic kidney disease (CKD) recommend using the Cockcroft?CGault (CG) or Modification of Diet in Renal Disease (MDRD) equations for calculating estimated glomerular filtration rate (eGFR) with the correction factor, 1.212, included for MDRD-eGFR in black patients. We compared eGFR against technetium-99m-diethylenetriaminepentaacetic acid (^99mTc-DTPA) imaging.

Methods

Using clinical records, we retrospectively recorded demographic, clinical, and laboratory data as well as ^99mTc-DTPA-measured GFR (mGFR) results obtained from routine visits. Data from 148 patients of African (n?=?91) and Indian (n?=?57) ancestry were analyzed.

Results

Median (IQR) mGFR was 38.5 (44) ml/min/1.73?m², with no statistical difference between African and Indian patients (P?=?0. 573). In African patients with stage 3 CKD, MDRD-eGFR (unadjusted for black ethnicity) overestimated mGFR by 5.3% [2.0 (16.0) ml/min/1.73?m²] compared to CG-eGFR and MDRD-eGFR (corrected for black ethnicity) that overestimated mGFR by 17.7% [6.0 (15.0) ml/min/1.73?m²] and 17.1% [6.0 (17.5) ml/min/1.73?m²], respectively. In stage 1?C2, CKD eGFR overestimated mGFR by 52.5, 38.0, and 19.3% for CG, MDRD (ethnicity-corrected), and MDRD (without correction), respectively. In Indian stage 3 CKD patients, MDRD-eGFR underestimated mGFR by 35.6% [?21.0 (6.5) ml/min/1.73?m²] and CG-eGFR by 4.4% [?2.0 (27.0) ml/min/1.73?m²], while in stage 1?C2 CKD, CG-eGFR and MDRD-eGFR overestimated mGFR by 13.8 and 6.3%, respectively.

Conclusion

MDRD-eGFR calculated without the African-American correction factor improved GFR prediction in African CKD patients and using the MDRD correction factor of 1.0 in Indian patients as in Caucasians may be inappropriate.