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Review of A1cNow+ point-of-care device for monitoring HbA1c
HbA1c values are typically measured by obtaining a venous blood draw in the office or laboratory, which can be time-consuming, costly and inconvenient for the patient.
Studies have shown the benefits of rapid HbA1c results at the time of the patient encounter by improving glucose control through intensification of therapy and improvement of HbA1c levels. Point of care HbA1c tests may allow for rapid HbA1c determination, but there must be sufficient evidence supporting their accuracy if they are used to guide therapy.
There are currently several HbA1c devices available to both patients and health care providers. Some provide results in minutes, while most require mailing in the sample collection to a laboratory (see table). This column reviews the A1cNow+ monitor (Metrika), a single use, disposable monitor designed for professional use only.
Results of clinical trials
Studies have been performed by the manufacturer, which compared the A1cNow+ to National Glycohemoglobin Standardization Program Certified Laboratories. One study involving 39 patients from a clinic group in Atlanta showed a correlation coefficient of 0.95. Further studies at large clinic groups involving 20 patients and 54 patients demonstrated correlation coefficients of 0.98 and 0.97, respectively.
We studied 70 patients with type 1 or type 2 diabetes enrolled from three pharmacist-managed diabetes clinics. Patients were required to have a venous blood draw within one week of the point-of-care test. We then evaluated the statistical and clinical significance between the A1cNow+ and a standard lab. Results showed a good correlation between the A1cNow+ and laboratory values with a correlation coefficient of r=0.893. The best correlation between the A1cNow+ and the lab was seen among HbA1c values ranging from 7% to 8.5%. The poorest correlation between the A1cNow+ and the lab was seen for HbA1c <7.5% as reported by the lab. One limitation to our study is the fact that relatively few patients had high HbA1c values (>8.5%). HbA1c values from the point of care test and standardized lab were obtained within seven days of one another, although it is unclear what effect this would have on HbA1c.
In a separate but similarly designed trial we evaluated 25 patients with type 1 or type 2 diabetes. Patients were required to obtain a standardized laboratory HbA1c evaluation and a point of care A1cNow value within a week of each other. At the end of the study, we completed an analysis evaluating the clinical and statistical significance. We found that the A1cNow monitor showed good correlation (r=0.758) to the standardized laboratory. We also found that the most accurate A1cNow values were found to be within an HbA1c range of 6% to 8%.
 James R. Taylor |
Kennedy et al performed a trial involving 7,758 subjects in which they compared the A1cNow to a standard lab. They found a correlation (r) of 0.72. The correlation was consistent even with higher mean (>8.5%) HbA1c values. Although the mean A1cNow and lab values were in good agreement, they found a large dispersion of individual HbA1c values. Therefore, the researchers concluded that the two methods should not be used interchangeably. At the time of this study the A1cNow was not National Glycohemoglobin Standardization Program certified. Improvements were subsequently made allowing it to now be National Glycohemoglobin Standardization Program certified.
Fox et al studied the A1cNow in 32 children with type 1 diabetes. They also measured HbA1c using the Bayer DCA2000 and a central laboratory. The correlation (r) for the A1cNow was 0.8 as compared to the laboratory. Additionally, 32% of the A1cNow values differed by more than 0.5% as compared to the laboratory. Incidentally, the correlation (r) for the Bayer DCA2000 was 0.99. The researchers concluded that they could not recommend the A1cNow for routine use.
Discussion
Aside from the convenience A1cNow+ offers, it may provide a cost advantage to a patient who is responsible for fee-for-service and to primary care clinics that use the device for HbA1c determination. The cost for evaluation of HbA1c from the central lab can range from $22 to $65 for a patient without insurance coverage. This does not include the additional lab draw fee of $10 to $20. The cost for a single test of HbA1c on average with A1cNow+ is $11.90. However, like most diabetic patients who have Medicare Part B, there are CPT codes available for reimbursement to the clinics. The Medicare National Limitation Amount is $21.06 in most states.
In the trials above, not including manufacturer studies, correlation for the A1cNow to standard lab ranged from 0.72 to 0.893. Three of studies used the older version, the A1cNow. The name was later changed to A1cNow+, though it is not clear if internal changes were made. The study with the best correlation used the A1cNow+, so perhaps this newer version is more accurate. Larger trials are needed to confirm this finding, which would allow health care providers to use this product more confidently in place of a standard lab HbA1c. Otherwise, the convenience and cost factors mean nothing if the product is not acceptably accurate. Of course, many times patients need other laboratory tests along with an HbA1c so this product would not eliminate the need for venous blood draws. The A1cNow+ does not currently report estimated average glucose values.
For more information:
- Arrendale JA, Cherian SE, Zineh I, et al. Assessment of glycated hemoglobin using A1cNow+ point-of-care device as compared to central laboratory testing. Journal of Diabetes Science and Technology. 2008;2:822-827.
- Bayer Healthcare website. www.a1cnow.com. Accessed September 26, 2008.
- Cagliero E, Levina E, Nathan DM. Immediate feedback of HbA1c levels improves glycemic control in type 1 and insulin treated type 2 diabetic patients. Diabetes Care. 1999;11:1785-1788.
- Fox L, Dontchev M, Ruedy K, et al. Relative inaccuracy of the A1cNow in children with type 1 diabetes. Diabetes Care. 2007;30:135-137.
- 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. 2005;7:907-912.
- Marrero DG, Kraft S, Fineberg N. Effect of immediate feedback of HbA1c on patient glycemic control and physicians’ treatment decisions (Abstract). Diabetes. 1996;45:7A.
- Sicard DA, Taylor JR. Comparison of Point-of-Care HbA1c Test versus Standardized Laboratory. Ann Pharmacother. 2005;39:1024-1028.
- 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. 1999;22:1415-1421.