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-Gault (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 ((99m)Tc-DTPA) imaging.

METHODS

Using clinical records, we retrospectively recorded demographic, clinical, and laboratory data as well as (99m)Tc-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 m(2), 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 m(2)] 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 m(2)] and 17.1% [6.0 (17.5) ml/min/1.73 m(2)], respectively. In stage 1-2, 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 m(2)] and CG-eGFR by 4.4% [-2.0 (27.0) ml/min/1.73 m(2)], while in stage 1-2 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.