Implementing a Modified Russell Two-Point Method to Measure Glomerular Filtration Rates (GFR)
Mentor 1
Aileen Staffaroni
Location
Union 179
Start Date
24-4-2015 1:20 PM
Description
Objective: Glomerular filtration rates (GFR) are usually acquired using nuclear medicine imaging techniques. Our laboratory initiated an additional non imaging GFR method (Russell two-point method) and compared the results to the established imaging method. Methods: A total of 11 standard imaging GFR patients were injected with 3.6 to 4.4 mCi Technetium-99m-Diethylenetriaminepentaacetic acid (radiochemical purities greater than 98%). Duplicate patient blood samples were obtained at 60 ± 2 min and 180 ± 2 min post injection and centrifuged. Separated plasma was pipetted into Merck Millipore Centrifugal Filter Units and centrifuged at high speed (6,000 rpm for 15 min) to remove radiolabeled DTPA bound protein. Duplicate aliquots of filtered and unfiltered plasma (0.1ml) were placed in test tubes, saline added (0.9 ml) and all samples counted using a sodium iodide (NaI) well detector interfaced to a multichannel analyzer. After test completion, the ratios of filtered plasma GFR to unfiltered plasma GFR values were statistically analyzed. Results: GFR values of the sample group ranged from 42.1-204.8 ml/min. The calculated mean ratio of filtered to unfiltered GFR values of 11 patient samples was 1.2 ± 0.06 and was subsequently used as our standard correction factor. As a result, when imaging GFR values were normal (greater than 90 ml/min), the modified Russell two-point method using unfiltered plasma and the standard correction factor (1.2) was used. When imaging GFR values were abnormal, less than 90 ml/min, the Russell two-point method with filtered plasma was used. Conclusion: A modified Russell two-point method was implemented to evaluate and compare glomerular filtration rates. When imaging GFR values were greater than 90 ml/min, plasma GFR was calculated with the ratio correction factor, and when values were below 90 ml/min the plasma GFR was calculated using filtered plasma.
Implementing a Modified Russell Two-Point Method to Measure Glomerular Filtration Rates (GFR)
Union 179
Objective: Glomerular filtration rates (GFR) are usually acquired using nuclear medicine imaging techniques. Our laboratory initiated an additional non imaging GFR method (Russell two-point method) and compared the results to the established imaging method. Methods: A total of 11 standard imaging GFR patients were injected with 3.6 to 4.4 mCi Technetium-99m-Diethylenetriaminepentaacetic acid (radiochemical purities greater than 98%). Duplicate patient blood samples were obtained at 60 ± 2 min and 180 ± 2 min post injection and centrifuged. Separated plasma was pipetted into Merck Millipore Centrifugal Filter Units and centrifuged at high speed (6,000 rpm for 15 min) to remove radiolabeled DTPA bound protein. Duplicate aliquots of filtered and unfiltered plasma (0.1ml) were placed in test tubes, saline added (0.9 ml) and all samples counted using a sodium iodide (NaI) well detector interfaced to a multichannel analyzer. After test completion, the ratios of filtered plasma GFR to unfiltered plasma GFR values were statistically analyzed. Results: GFR values of the sample group ranged from 42.1-204.8 ml/min. The calculated mean ratio of filtered to unfiltered GFR values of 11 patient samples was 1.2 ± 0.06 and was subsequently used as our standard correction factor. As a result, when imaging GFR values were normal (greater than 90 ml/min), the modified Russell two-point method using unfiltered plasma and the standard correction factor (1.2) was used. When imaging GFR values were abnormal, less than 90 ml/min, the Russell two-point method with filtered plasma was used. Conclusion: A modified Russell two-point method was implemented to evaluate and compare glomerular filtration rates. When imaging GFR values were greater than 90 ml/min, plasma GFR was calculated with the ratio correction factor, and when values were below 90 ml/min the plasma GFR was calculated using filtered plasma.
