GFR Estimation and Correlation for Oncology Patients by Two Methods, Gates Method and Dual Time Point Plasma Sampling Method.

Background: With the increasing number of oncology cases and a parallel surge in chemotherapeutic drugs for treatment, the treating physicians conducts nephrotoxicity evaluation to provide a personalized dosing strategy. Of the various tests available, glomerular filtration rate (GFR) under gamma camera with help of Gates method has gained importance, being a good index of overall kidney functions. In addition to this, there has been an alternate and old method for GFR estimation: plasma sampling. We at our Institution conducted both the methods for better evaluation of GFR in cancer patient management.

Aim: Comparison of Gates' camera based GFR based on kidney depth correction using Tonessen's method and CT based manual depth calculation with dual time point plasma sampling in cancer patients.

Method: A retrospective study wherein patients' database were evaluated over a period of four months after approval from our Institutional Review Board. Thirty patients were included in the study. GFR was evaluated by two methods: Gates camera based and dual time plasma sampling method. Statistical analysis was done to help evaluate a correlation coefficient between the methods (Gates' method with and without CT based manual depth correction and dual time point plasma sampling).

Results: Our study showed moderate correlation between Gates' camera based GFR and dual time plasma sampling method.

Conclusion: One need to understand the limitation of each method and see if the renal depth corrections can be done with the help of CT or lateral images of NM for near accurate GFR and in case of selecting dual plasma sampling, errors to be minimized in pipetting and sample counting. Hence, it will be better to use both the methods for coming to a conclusion.