Abstract
2045
Objectives: Glomerular filtration rate (GFR) has become an increasingly important factor in assessing overall renal perfusion and function. Currently, the Society of Nuclear Medicine and Molecular Imaging (SNMMI) has no specific protocol for retrieving GFR and therefore nuclear medicine (NM) departments follow varying protocols. Common practice for many NM departments includes retrieving a plasma sample and then collecting an additional filtered plasma sample termed “ultrafiltrate” at one and three hours post-injection. Then, a final GFR is reported based on the three hour post-injection ultrafiltrate sample. The purpose of this research study is to compare unfiltered plasma GFR values and ultrafiltrate GFR values in order to evaluate whether collecting an additional filtered plasma sample is necessary and beneficial.
Methods: Following HIPPA guidelines, body surface area corrected GFR values recorded between June 2016 and October 2018 were collected retrospectively from 180 patient charts. Values including three hours post-injection plasma GFR and three hours post-injection ultrafiltrate GFR (cc/min) were recorded and compared utilizing a paired t-test. The difference between each value was then quantified utilizing a percent change calculation.
Results: The paired t-test yielded a t-critical value of 1.650 at an alpha level of 0.05 for 179 degrees of freedom and a p-value of <0.001. The average percent increase in GFR between plasma samples and ultra-filtered samples was 6.049% with a standard deviation of 0.076%.
Conclusions: Because the paired t-test produced a p-value of <0.05, the null hypothesis that there is no statistical difference in GFR between original plasma samples and ultrafiltrate samples was rejected. Although there is a statistical difference, this variance is relatively static between samples and may possibly be incorporated into formulas used to calculate GFR. Additional studies could be performed to confirm the uniformity in the percent difference between filtered and unfiltered samples. Furthermore, subsequent studies could be carried out to determine which set of calculated GFR values is more accurate. Ultimately, collecting an additional ultrafiltrate sample three hours post-injection may be beneficial for NM departments to more accurately determine patient GFR values. Accurate GFR determination aids in assessing the potential for rejection in prospective kidney donors, and also allows health care professionals to formulate the best course of treatment for patients in renal failure.