Prediction of renal function improvement in azotemic patients using glomerular filtration rate from 99mTc-DTPA renal scan: an observational study

Abstract

Objective: This study aimed to evaluate the ratio of glomerular filtration rate (GFR) from 99mTc-DTPA dynamic renal scan (GFRSCAN) to estimated GFR (eGFR) as a predictor of renal function improvement in patients with azotemia. Methods: A retrospective review of medical records was conducted to identify consecutive patients with newly discovered or aggravated azotemia who underwent 99mTc-DTPA renal scan. Significant renal function improvement was defined as ≥100% and ≥10 ml/min improvement of eGFR at 12 weeks compared to eGFR on the day of renal scan (eGFR0). The GFRSCAN/eGFR0 ratio was evaluated as a predictor of significant renal function improvement using logistic regression and receiver operating characteristic (ROC) curve analyses. Added value of the GFRSCAN/eGFR0 ratio in the prediction of significant renal function improvement were demonstrated by adjusting for best clinical predictor variables. Results: The eligibility criteria were met by 224 patients, among whom 22 patients (9.8%) showed significant renal function improvement. The odds ratios of the GFRSCAN/eGFR0 ratio for predicting significant renal function improvement were 1.76 (95% confidence interval [CI]: 1.26?2.45, p<.001) in the univariable analysis and 1.70 (95% CI: 1.19?2.42, p=.003) after adjusting for clinical variables. The area under the ROC curve (AUC) of the GFRSCAN/eGFR0 ratio for predicting significant renal function improvement was 0.762 (95% CI: 0.648?0.871). The addition of the GFRSCAN/eGFR0 ratio to the best clinical prediction model raised the AUC from 0.726 to 0.794, and this increment was statistically significant (p=.02). Conclusion: The GFRSCAN/eGFR ratio can predict renal function improvement in patients with azotemia. Future prospective studies are necessary to validate its potential clinical utilities.