Accuracy of a Point-of Care Hemoglobin A1c Assay - A Community Outreach Project

Abstract

Glycated hemoglobin (HbA1c) is an invaluable tool in diabetes mellitus (DM) management. Conventionally obtained via venous blood sampling, point-of-care (POCT) capillary HbA1c measurement offers an opportunity for immediate treatment modification, reduced cost & increased patient satisfaction. While previous studies using the POCT HbA1c test A1cNow+ have shown accuracy within a 0.5% range from the gold standard venous HbA1c, we noted discrepancy in our community health clinic & sought to evaluate the accuracy of POCT HbA1c levels compared to venous HbA1c levels to guide our clinical decision-making.In this 2-part study, we compared POCT HbA1c levels measured via a single use A1CNow+ HbA1c monitoring device & venous HbA1c samples measured by a standardized lab. Part1: after retrospective chart review, we identified 262 patients with prediabetes, Type1 or Type2 DM based on ADA guidelines who attended our clinic from January 2019-June 2019 & received POCT HbA1c with A1cNow+ testing during their visit. Of those cases, 47 patients also had a venous HbA1c at a standardized laboratory within 1 month of having their POCT HbA1c performed in our clinic. Part2: We noted variability in the temperature storage of A1CNow+ test strips. Storage was standardized to room temperature as per device instructions in June 2019. We subsequently reviewed charts from June 2019-December 2019 & identified 118 patients who had both POCT HbA1c & venous HbA1c measurement within a 1 month period.Patients was categorized into subgroups per ACP guidelines for DM control: prediabetic (HbA1c 5.7–6.4%), controlled DM (HbA1c 6.5 to 8.0%) & uncontrolled DM (HbA1c >8.0%). The average difference between POCT & venous HbA1c tests was calculated & analyzed for statistical significance using paired t test analysis. Part1: For patients in prediabetic, controlled & uncontrolled DM subgroups, the mean difference between A1cNow+ & standardized venous HbA1c testing was 0.68% (p= 0.004), 1.15% (p= <0.0001) and 1.36% (p= 0.0003) respectively. Part2: After standardization of test strip storage, the mean difference between A1cNow+ & venous HbA1c testing for prediabetic, controlled & uncontrolled DM patients was 0.33% (p= 0.002), 0.41% (p= 0.011) and 1.26% (p= <0.0001) respectively.POCT HbA1c provides a unique opportunity to immediately address glycemic control. Its advantages are especially apparent in a patient population with limited resources & poor follow up, as in our clinic. Although standardizing test storage improved overall concordance between A1cNow+ HbA1c testing & venous HbA1c, there was still a statistically significant larger mean difference in uncontrolled DM patients. In prediabetic & controlled DM patients, however, POCT HbA1c was accurate within previously published reports of a 0.5% range when compared to venous HbA1c. An algorithm has since been developed to guide our clinical decision making with these findings.