Correlation of Glomerular Filtration Rate Between Renal Scan and Estimation Equation for Patients With Scleroderma

Renal involvement in scleroderma is life-threatening. Early detection of a deterioration of the glomerular filtration rate (GFR) is needed to preserve kidney function.

To (A) determine the correlation between (1) estimated GFR (eGFR) using 4 different formulae and (2) measured GFR (mGFR) using isotopic renal scan in Thai patients with scleroderma with normal serum creatinine and (B) to define the factors influencing eGFR.

A cross-sectional study was performed in adult Thai patients with scleroderma at Srinagarind Hospital, Khon Kaen University, between December 2013 and April 2015. GFR was measured using the gold standard Tc-99m DTPA (Tc-99m diethylenetriaminepentaacetic acid) renal scan. We compared the latter with the eGFR, calculated using the Cockroft-Gault formula, Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and creatinine clearance equation.

A total of 76 patients with scleroderma (50 women and 26 men) with median age 54.8 years (interquartile range: 47.4 to 58.9) were enrolled. Mean disease duration was 5.6 ± 4.5 years. Median value of mGFR was 100.1 ± 27.6mL/minute/1.73m². There was a correlation between mGFR from the Tc-99m DTPA renal scan and the eGFR using the Cockroft-Gault formula, MDRD and CKD-EPI equation (P = 0.01, <0.001 and <0.001, respectively), but no correlation with eGFR using the creatinine clearance equation (P = 0.27). Body weight, prednisolone use and systolic blood pressure (SBP) had a negative association with mGFR (P = 0.01, 0.01 and 0.007, respectively). After multivariate analysis, SBP was the only clinical parameter that influenced mGFR (P = 0.03).

The Cockroft-Gault formula, MDRD study equation and CKD-EPI were useful formulae for assessing GFR in Thai patients with scleroderma. Higher SBP was associated with a lower GFR.