Presentation on theme: "Accuracy of the A1cNow ® in Children with T1D. Diabetes Research in Children Network Larry Fox, 1 Dongyuan Xing, 2 Katrina Ruedy, 2 Roy Beck, 2 Craig Kollman,"— Presentation transcript:
Accuracy of the A1cNow ® in Children with T1D. Diabetes Research in Children Network Larry Fox, 1 Dongyuan Xing, 2 Katrina Ruedy, 2 Roy Beck, 2 Craig Kollman, 2 Laurel Messer, 3 Julie Coffey, 4 Jen Block, 5 Elizabeth Doyle, 6 William Tamborlane 6 for the Diabetes Research in Children (DirecNet) Study Group. 1 Jacksonville, FL; 2 Tampa, FL; 3 Denver, CO; 4 Iowa City, IA; 5 Stanford, CA; 6 New Haven, CT. Supported by NIH/NICHD Grants HD041919,HD041915,HD041890,HD041918,HD041908, HD041906; GCRC Grants RR00069,RR00059,RR06022,RR00070; Nemours Research Programs.
Introduction Hemoglobin A1c (A1c) has been used extensively as a risk marker for microvascular complications in people with diabetes. The Diabetes Control and Complications Trial (DCCT) and its follow up study, Epidemiology of Diabetes Intervention and Complications (EDIC), established a standard for measuring A1c levels, using high-performance liquid chromatography (HPLC). 1 Several studies have demonstrated the benefit of point-of-care, A1c testing, i.e., while still face-to- face with the patient/family in the clinic setting. 2-4
Introduction (cont’d) The DCA2000® Analyzer (Bayer, Inc., Tarrytown, NY) uses an immunoassay method certified by the National Glycohemoglobin Standardization Program (NGSP). 5 Use of DCA2000 as a point-of-care assessment tool is becoming the standard of care for people with diabetes. In our previous study, the DCA2000 correlated well with DCCT/EDIC reference values (r=0.94, p<0.001). 6
Introduction (cont’d) A1cNow® (Metrika, Inc., Sunnyvale, CA) was developed as a single-use, disposable test for measuring A1c at home. The A1cNow requires one drop of blood to perform the test, and uses an immunoassay method. Results are displayed in approximately 8 min. The currently available A1cNow is NGSP-certified. There has been only one published study 7 assessing the accuracy of the A1cNow, but: –an older generation, non-NGSP-certified A1cNow device was used. –no comparison to the DCA2000 was included.
Study Aim Compare the accuracy of updated, NGSP-certified A1cNow devices with the DCA2000 and DCCT/EDIC laboratory reference values when used at home and during an inpatient setting in children with type 1 diabetes (T1D).
Methods The study was conducted at the five DirecNet clinical centers in 32 children with T1D. IRB approval and informed consent were obtained. HbA1c was measured four times using the A1cNow, twice by the subject or parent at home and twice the following day by site staff at a clinic visit. Commercially available A1cNow monitors were used. Subjects were given the manufacturer’s instructions; no additional instructions were provided by site staff. At the clinic visit, A1c was measured using the DCA2000 and a fingerstick blood sample was obtained, frozen at -70°C, and shipped to the DirecNet Central Laboratory at the University of Minnesota where measurements were performed using cation-exchange HPLC methodology.
Results Study subject characteristics are shown in table 1. Comparison of A1cNow and DCA2000 results are shown in table 2. 32% percent of the A1cNow values differed from the reference by >0.5%, vs. 3% of the DCA2000 values (p=0.009). There were no meaningful differences in accuracy between subject/parent and staff measurements.
Results (cont’d) 32% of simultaneous A1cNow measurements made at home (n=25) & 34% of the simultaneous measurements at the clinic (n=29) differed by more than 0.5%. Accuracy of the A1cNow did not vary with A1c level (p=0.23) (figure). –the A1cNow was within 0.5% in 74% of reference values ≥8.0% and 67% of reference values <8.0%. Accuracy of the A1cNow did not vary with the current glucose level (data not shown).
Table 1. Demographics of study subjects * * Values for age and A1c are mean±S.D. N32 Age14.5 ± 2.1 Female13 (41%) Caucasian29 (91%) Baseline A1c7.5 ± 0.9 A1c <7.0%9 (28%) A1c 7.0-7.9%13 (41%) A1c ≥8.0%10 (31%)
Table 2. A1cNow and DCA2000 Accuracy. ComparisonN* Median DifferenceMAD § Within ±0.1 Within ±0.3 Within ±0.5 A1cNow (subject) vs. Lab550.00.415%42%69% A1cNow (staff) vs. Lab610.00.413%41%67% A1cNow (pooled) vs. Lab1160.00.414%41%68% DCA2000 vs. Laboratory32+0.20.225%84%97% 2 Simultaneous A1cNow Values Performed by subjects25N/A0.316%56%68% Performed by staff29N/A0.417%45%66% *Number of pairs; may include multiple pairs per subject. § MAD, median absolute difference.
Figure. A1cNow and DCA2000 vs. Laboratory Reference. Laboratory Reference A1c (%) A1cNow or DCA2000 Result (%)
Discussion The present study indicates that the A1cNow is not as accurate as the DCA2000 when compared to reference values using standard HPLC methods. A substantial proportion of A1cNow measurements differ from the reference values by >0.5%, whereas only a small amount (3%) of DCA2000 values differed from the reference value by >0.5%.
Discussion (cont’d) There were marked differences in A1cNow values when two simultaneous measurements were made, either at home by the parents or in the clinic setting by the study staff. This lack of consistency amongst simultaneous A1cNow values does not likely reflect user-to- user differences. –instead relates to problems inherent to the A1cNow, even though the kits we used were NGSP certified.
Conclusion The A1cNow is not as accurate as the DCA2000. A substantial proportion of A1cNow measurements differ from a reference value by >0.5%. The lack of reproducibility limits the use of the A1cNow in the clinical setting in children with T1D.
References 1.The DCCT Research Group. Feasibility of centralized measurements of glycated hemoglobin in the Diabetes Control and Complications Trial: a multicenter study. Clin Chem 33: 2267-2271, 1987. 2.Cagliero E, Levina EV, Nathan DM. Immediate feedback of HbA1c levels improves glycemic control in type 1 and insulin-treated type 2 diabetic patients. Diabetes Care 22:1785–1789, 1999. 3.Thaler LM, Ziemer DC, Gallina DL, et al. Diabetes in urban African-Americans. XVII. Availability of rapid HbA1c measurements enhances clinical decision- making. Diabetes Care 22:1415–1421, 1999. 4.Miller CD, Barnes CS, Phillips LS, et al. Rapid A1c availability improves clinical decision-making in an urban primary care clinic. Diabetes Care 26:1158–1163, 2003. 5.Little RR. Glycated hemoglobin standardization – National Glycohemoglobin Standardization Program (NGSP) perspective. Clin Chem Lab Med 41:1191- 1198, 2003. 6.DirecNet Study Group. Comparison of fingerstick hemoglobin A1c levels assayed by DCA2000 with the DCCT/EDIC central laboratory assay: results of a Diabetes Research in Children Network (DirecNet) study. Pediatric Diabetes 6:13-16, 2005. 7.Kennedy L, Herman WH. Glycated Hemoglobin Assessment in Clinical Practice: Comparison of the A1cNow™ Point-of-Care Device with Central Laboratory Testing (GOAL A1C Study). Diabetes Technol & Ther 7:907-912, 2005.
Barbara Davis Center –H. Peter Chase –Rosanna Fiallo-Scharer –Laurel Messer –Barbara Tallant University of Iowa –Eva Tsalikian –Michael Tansey –Linda Larson –Julie Coffey –Joanne Cabbage Nemours Children’s Clinic –Tim Wysocki –Nelly Mauras –Larry Fox –Keisha Bird –Kim Englert Stanford University –Bruce Buckingham –Darrell Wilson –Jennifer Block –Paula Clinton Yale University –William Tamborlane –Stuart Weinzimer –Elizabeth Doyle –Melody Martin –Amy Steffen Jaeb Center for Health Research –Roy Beck –Katrina Ruedy –Craig Kollman –Dongyuan Xing –Cynthia Stockdale