Accuracy of the A1cNow in Children with T1D'

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Accuracy of the A1cNowin 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
Tamborlane6 for the Diabetes Research in Children
(DirecNet) Study Group. 1Jacksonville, FL
2Tampa, FL  3Denver, CO 4Iowa City, IA
5Stanford, CA 6New Haven, CT.
Supported by NIH/NICHD Grants HD041919,HD041915,HD
041890,HD041918,HD041908, HD041906 GCRC Grants
RR00069,RR00059,RR06022,RR00070 Nemours Research
Programs.
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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

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Introduction (contd)

• 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 (r0.94,
  plt0.001).6

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Introduction (contd)

• 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 study7
  assessing the accuracy of the A1cNow, but
• an older generation, non-NGSP-certified A1cNow
  device was used.
• no comparison to the DCA2000 was included.

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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).

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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 manufacturers
  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 -70C, and shipped to the
  DirecNet Central Laboratory at the University of
  Minnesota where measurements were performed using
  cation-exchange HPLC methodology.

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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 gt0.5, vs. 3 of the DCA2000
  values (p0.009).
• There were no meaningful differences in accuracy
  between subject/parent and staff measurements.

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Results (contd)

• 32 of simultaneous A1cNow measurements made at
  home (n25) 34 of the simultaneous
  measurements at the clinic (n29) differed by
  more than 0.5.
• Accuracy of the A1cNow did not vary with A1c
  level (p0.23) (figure).
• the A1cNow was within 0.5 in 74 of reference
  values 8.0 and 67 of reference values lt8.0.
• Accuracy of the A1cNow did not vary with the
  current glucose level (data not shown).

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Table 1. Demographics of study subjects

• N 32
• Age 14.5 2.1
• Female 13 (41)
• Caucasian 29 (91)
• Baseline A1c 7.5 0.9
• A1c lt7.0 9 (28)
• A1c 7.0-7.9 13 (41)
• A1c 8.0 10 (31)

Values for age and A1c are meanS.D.
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Table 2. A1cNow and DCA2000 Accuracy.
Number of pairs may include multiple pairs per
subject. MAD, median absolute difference.
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Figure. A1cNow and DCA2000 vs. Laboratory
Reference.
A1cNow or DCA2000 Result ()
Laboratory Reference A1c ()
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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 gt0.5,
  whereas only a small amount (3) of DCA2000
  values differed from the reference value by gt0.5.

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Discussion (contd)

• 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.

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Conclusion

• The A1cNow is not as accurate as the DCA2000.
• A substantial proportion of A1cNow measurements
  differ from a reference value by gt0.5.
• The lack of reproducibility limits the use of the
  A1cNow in the clinical setting in children with
  T1D.

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References

• 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.
• 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 2217851789,
  1999.
• 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 2214151421,
  1999.
• Miller CD, Barnes CS, Phillips LS, et al. Rapid
  A1c availability improves clinical
  decision-making in an urban primary care clinic.
  Diabetes Care 2611581163, 2003.
• Little RR. Glycated hemoglobin standardization
  National Glycohemoglobin Standardization Program
  (NGSP) perspective. Clin Chem Lab Med
  411191-1198, 2003.
• 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 613-16, 2005.
• 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 7907-912, 2005.

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• 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 Childrens 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

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