Accuracy and the Proper Use of the Point-of-Care Analysis in Hemoglobin A1C Measurement

Background: Diabetes Mellitus is one of the most common chronic diseases in the United States and worldwide. In 2009 the American Diabetes Association (ADA) recommended using A1C greater than 6.5% to diagnose diabetes. Hemoglobin A1C can be measured by laboratory and Point-of-Care (POC) methods. It is important to compare results obtained by the two modalities to determine the proper use of these tests. Methods: One hundred fifteen patients were identified to have both POC and laboratory A1C values obtained on the same day, between August 2013 and August 2014. The differences were analyzed and the average difference and coefficient of determination (R-2) was calculated. In addition, a Bland-Altman plot was generated; Kappa statistic calculated. We also computed the sensitivity and specificity of the POC method in diagnosing diabetes while using laboratory analysis as the gold standard. Results: The differences between the two measurements ranged from 0 to 3.2 with an average difference of 0.2% of A1C. The Kappa statistic is 0.761 and R-2 was 0.938. Laboratory results were greater than POC in 84% of cases. Interestingly, the Bland-Altman graph also indicates that the variability between the two sets of data increases with higher values of A1C especially for A1C greater than 10%. The POC method has a sensitivity of 88.6% and specificity of 96.3% in diagnosing diabetes. Conclusions: Per ADA guidelines, the POC method is not recommended to be used to diagnose diabetes. Based on our findings 10.3% of individuals would be missed if one used the POC method to diagnose diabetes. However, given its accuracy supported by our findings it is adequate to be used during routine diabetes follow-up visits. The finding from our study can help improve healthcare quality by reducing unnecessary blood draws and clinic visits.