Transcript A1cNow or DCA2000 Result - Jaeb Center for Health Research

®
A1cNow
Accuracy of the
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 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,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-toface 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 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.
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*
N
Age
Female
Caucasian
Baseline A1c
A1c <7.0%
A1c 7.0-7.9%
A1c ≥8.0%
* Values for age and A1c are mean±S.D.
32
14.5 ± 2.1
13 (41%)
29 (91%)
7.5 ± 0.9
9 (28%)
13 (41%)
10 (31%)
Table 2. A1cNow and DCA2000 Accuracy.
N*
Median
Difference
MAD§
Within
±0.1
Within
±0.3
Within
±0.5
A1cNow (subject) vs. Lab
55
0.0
0.4
15%
42%
69%
A1cNow (staff) vs. Lab
61
0.0
0.4
13%
41%
67%
A1cNow (pooled) vs. Lab
116
0.0
0.4
14%
41%
68%
DCA2000 vs. Laboratory
32
+0.2
0.2
25%
84%
97%
Performed by subjects
25
N/A
0.3
16%
56%
68%
Performed by staff
29
N/A
0.4
17%
45%
66%
Comparison
2 Simultaneous A1cNow Values
*Number of pairs; may include multiple pairs per subject.
§ MAD,
median absolute difference.
Figure. A1cNow and DCA2000 vs. Laboratory Reference.
A1cNow or DCA2000 Result (%)
10
A1cNow (subject)
A1cNow (staff)
DCA2000
9
8
7
6
5
5
6
7
8
9
Laboratory Reference A1c (%)
10
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-touser 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 decisionmaking. 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 41:11911198, 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
•
Stanford University
– Bruce Buckingham
– Darrell Wilson
– Jennifer Block
– Paula Clinton
•
University of Iowa
– Eva Tsalikian
– Michael Tansey
– Linda Larson
– Julie Coffey
– Joanne Cabbage
•
Yale University
– William Tamborlane
– Stuart Weinzimer
– Elizabeth Doyle
– Melody Martin
– Amy Steffen
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Nemours Children’s Clinic
– Tim Wysocki
– Nelly Mauras
– Larry Fox
– Keisha Bird
– Kim Englert
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Jaeb Center for Health Research
– Roy Beck
– Katrina Ruedy
– Craig Kollman
– Dongyuan Xing
– Cynthia Stockdale