Concordance between estimated glomerular filtration rate using equations and that measured using an imaging method

Background: Guidelines recommend estimating glomerular filtration rate (GFR) using creatinine-based equations (CBE). Aim: To evaluate the agreement between GFR measured using radionuclide imaging and estimated using creatinine-based equations. Material and Methods: In 421 patients aged 54 ± 17 years (47% women) GFR was estimated using the MDRD-4, CKD-EPI and the body surface adjusted Cockroft Gault equation. GFR was also measured using a radionuclide imaging method with 99mTc-DTPA. The concordance between estimated and measured GFR was calculated using Lin's concordance coefficient and Bland and Altman plots. Results: Average GFR values obtained with CKD-EPI, MDRD-4, body surface adjusted Cockroft Gault equation and 99mTc-DTPA imaging were 75.9 ± 26.6, 76.3 ± 28.8, 77.1 ± 31.6 and 77.9 ± 28.4 ml/min/1.73 m2, respectively. There was no significant difference in means and 29% of participants had a GFR < 60 ml/min/1.73 m2 by CKD-EPI. The correlation was good between equations, but acceptable when compared with the 99mTc-DTPA imaging. The weighted kappa between CBEs was good, but low when comparing CBEs with measured GFR. The Lin's concordance coefficient between estimated and measured GFR was low. Conclusions: GFR measured by 99mTc-DTPA radionuclide imaging has a low correlation and poor concordance with estimations using CBE.