This study was designed to identify a screening tool that would capture prediabetes or diabetes in a nonfasting, high-risk population. Because the ADA diagnostic criteria require two abnormal laboratory values on separate occasions, a major limitation of this study was that participants were screened using a POC device and then diagnosed based on one laboratory encounter. Individuals identified during this study were further evaluated by their medical provider as needed. Another limitation was that a POC A1C value greater than 5.7% (i.e., 5.8%) was used to define a positive POC A1C screening. The ADA diagnostic criterion for prediabetes is inclusive of an A1C of 5.7% (5.7–6.4%). Although this discrepancy is a limitation when interpreting our results, our analysis was actually more conservative and, despite this discrepancy, supports the need for a nonfasting screening tool that captures prediabetes. An additional 16 individuals would have been considered to have screened positive if the POC A1C value of 5.7% had been included in our criterion.
Financial constraints limited the screening sample size to approximately 200 individuals. Initially, follow-up venipuncture lab work was at the cost of the participant. This limitation negatively affected our follow-up rates, as workers were less likely to attend follow-up appointments early in the study. When funding became available, more workers presented for follow-up lab work even though it had been greater than 2 weeks since the initial screening.
Although certain hemoglobinopathies and iron deficiency anemia may interfere with obtaining accurate A1C results, these conditions were not screened for during the study. While the findings are specific to a Hispanic population, it is likely that POC A1C would help identify more individuals than RPG in other nonfasting, high-risk populations. Although the specific incidence in this study cannot be applied to all populations, the results suggest that POC A1C should be further studied to evaluate its use as a POC screening tool.