CLASSIFICATION OF CHRONIC KIDNEY DISEASE USING BERLIN INITIATIVE STUDY 1 EQUATION FOR ELDERLY AND SALAZAR CORCORAN EQUATION FOR OBESE SUBJECTS

Abstract

Objective: According to recent guidelines glomerular filtration rate (GFR) should be estimated using CKD-Epi equation for all subjects and all subgroups. Discussion whether this equation is appropriate for elderly where GFR is decreasing by aging and for obese who have higher body surface area (BSA) is going on. Recently, Berlin Initiative Study 1 equation (BIS1) and Salazar-Corcoran equation (S-C) were suggested to be more appropriate in elderly and obese subjects, respectively. Our aim was to analyze difference in estimation GFR when using CKD-EPI, BIS1 and S-C equations. Design and method: Data on 993 adult subjects (random sample of rural population;383 >=70 yr 610-BMI>=30) were analyzed. CKD-EPI, BIS1 and S-C were used to estimate eGFR in total group, elderly and obese, respectively. Differences between equations was analyzed using kappa inter-rater agreement and Bland-Altman plot analysis. Results: Significant difference in proportion of patients in CKD stages when comparing CKD-EPI vs BIS1 for subjects older than 70 yrs, p < 0.001 and CKD-EPI vs S-C for subjects with BMI>=30, p < 0.001 was observed (Table). BIS1 showed a downward reclassification with lower eGFR using BIS1 for stages 3a and 3b. The agreement between equations was moderate for BIS1 (kappa 0.56) and good for S-C (kappa 0.66). BIS1 classified 22.7% subjects more to a GFR < 60 than CKD-EPI. A systematic difference was found between the formulas, with BIS1 mean value 8.0 ml/min being lower than that of CKD-EPI (95% limits of agreement: +1.9 to -17.8) and S-C mean value 17.6 ml/min being lower than that of CKD-EPI (95% limits of agreement: +48.1 to -12.9).Conclusions: Significant difference in BIS1 and S-C formula comparing to CKD-EPI were found. Our results suggest that specific equations should be used in elderly and obese subjects. However, both equations should be further evaluated.