Geldmaker, Laura E

ObjectiveTo validate a new baseline estimated glomerular filtration rate (NB‐GFR) formula in a cohort of robotic‐assisted partial nephrectomies (RAPN).MethodsNB‐GFR = 35 + preoperative GFR (× 0.65) – 18 (if radical nephrectomy) – age (× 0.25) + 3 (if tumor size >7 cm) – 2 (if diabetes). NB‐GFR was calculated in 464 consecutive RAPN from a single surgeon cohort. 143 patients were excluded secondary to insufficient eGFR follow up. We analyzed NB‐GFR accuracy utilizing the last observed eGFR 3–12 months post RAPN. Categorical variables were summarized with the frequency and percentage of patients. Numerical variables were summarized with the median, 25th percentile, and 75th percentile.ResultsThe mean difference between observed and predicted NB‐GFR was 4.6 ml/min/1.73m2 (95% CI −6.9 to 16.1 ml/min/1.73m2). There was a pattern of higher observed NB‐GFRs being underestimated by the NB‐GFR equation while lower observed NB‐GFRs were overestimated by the NB‐GFR equation. The NB‐GFR formula had a high level of accuracy with 98.8% of predicted NB‐GFRs falling within 30% of the observed NB‐GFR (95% CI 86.8% to 99.5%). The median and interquartile range of the difference between observed and predicted NB‐GFR was 3.9 ml/min/1.73m2 (IQR 0.7 to 8.2 ml/min/1.73m2). The sensitivity, specificity, positive predictive value, and negative predictive value for the ability of predicted NB‐GFR to identify those with an observed NB‐GFR <60 ml/min/1.73m2 after RAPN was 98%, 92%, 88%, and 99%, respectively.ConclusionThe NB‐GFR equation developed with partial and radical nephrectomy cohorts is accurate in predicting post‐operative eGFR 3–12 months following RAPN.