Measured GFR in Routine Clinical Practice—The Promise of Dried Blood Spots  Petter Bjornstad, Amy B. Karger, David M. Maahs  Advances in Chronic Kidney Disease  Volume 25, Issue 1, Pages 76-83 (January 2018) DOI: 10.1053/j.ackd.2017.09.003 Copyright © 2017 National Kidney Foundation, Inc. Terms and Conditions

Figure 1 Comparison between GFR-DBS and GFR by iohexol clearance in plasma, Bland–Altman plots of the mean difference (dashed line), and 95% CI (dotted line) between each DBS by 2-time points and 5-time points minus the gold standard (GFR by iohexol clearance measured in plasma) plotted against the mean of the two measures. Abbreviations: CI, confidence interval; DBS, dried capillary blood spots; GFR, glomerular filtration rate; GFR-DBS, GFR measured in DBS. Figure adapted and modified from Maahs DM, Bushman L, Kerr B, Ellis SL, Pyle L, McFann K, et al. A practical method to measure GFR in people with type 1 diabetes. J Diabetes Complications. 2014; 28(5):667-73. Advances in Chronic Kidney Disease 2018 25, 76-83DOI: (10.1053/j.ackd.2017.09.003) Copyright © 2017 National Kidney Foundation, Inc. Terms and Conditions

Figure 2 Example of GFR-DBS sample collection algorithm. Abbreviations: DBS, dried capillary blood spots; GFR, glomerular filtration rate; GFR-DBS, GFR measured in DBS; HPLC, high-performance liquid chromatography; LC-MS/MS, liquid chromatography tandem mass spectrometry. Advances in Chronic Kidney Disease 2018 25, 76-83DOI: (10.1053/j.ackd.2017.09.003) Copyright © 2017 National Kidney Foundation, Inc. Terms and Conditions

Figure 3 Examples of unacceptable, acceptable, and ideal DBS, The DBS on the left represents an unacceptable spot, due to the small amount of blood, layering and abrasion of the sample which degrades sample quality. The DBS in the center is an acceptable spot for analysis—the blood does not quite reach the edges of the spot, but it is adequate in size to provide reasonably accurate results. The DBS on the right is an example of an ideal blood spot which is uniform in color and touches the edges of the entire circle. Abbreviation: DBS, dried capillary blood spots. Advances in Chronic Kidney Disease 2018 25, 76-83DOI: (10.1053/j.ackd.2017.09.003) Copyright © 2017 National Kidney Foundation, Inc. Terms and Conditions