Abstract and Introduction
Abstract
Objective: To compare point-of-care (POC) glycosylated hemoglobin (A1C) and random plasma glucose (RPG) as a POC screening tool for prediabetes and diabetes in migrant farm workers of eastern North Carolina.
Design: Prospective, observational, single-center study.
Setting: Federally qualified community health center in eastern North Carolina, from August to October 2011.
Participants: Migrant farm workers 18 years or older who resided in a migrant camp in eastern North Carolina.
Intervention: Diabetes screening using POC A1C and RPG via fingerstick followed by venipuncture A1C and basic metabolic panel in individuals with a positive screening.
Main outcome measures: Positive predictive value (PPV) of POC A1C and RPG, incidence of positive screening, incidence of confirmed diagnosis, concordance rate of the screening tools, and correlation between POC A1C and laboratory A1C.
Results: 206 workers participated in the screenings; screening identified 39 individuals with a POC A1C greater than 5.7% and 1 individual with both an RPG of 200 mg/dL or more and a POC A1C greater than 5.7%. Of the 39 individuals found to have a positive screening, 24 presented to Carolina Family Health Centers, Inc., for follow-up venipuncture; however, 1 participant did not have a venipuncture A1C, leaving 23 individuals with complete data. Two participants were diagnosed with diabetes and 17 with prediabetes. POC A1C had a PPV of 82.6%; however, the PPV of RPG could not be calculated due to the number of participants lost to follow-up. POC A1C correlated well with laboratory A1C regardless of time to follow-up.
Conclusion: POC A1C should be considered for diabetes screening in highrisk populations. If the screening had been performed with RPG alone, 38 individuals would have gone undetected. Early identification of individuals with elevated blood glucose will likely decrease the risk of long-term complications.
Introduction
Approximately one-fourth of all individuals with diabetes in the United States may be undiagnosed, which affects individuals' long-term prognosis considerably. Unfortunately, diabetes often is undiagnosed until complications occur, including retinopathy, neuropathy, and nephropathy. Therefore, early detection is essential to minimize the risks of these outcomes.
Screening for diabetes is recommended in asymptomatic individuals who are considered overweight and have at least one other risk factor, including high-risk race or ethnicity. Individuals 45 years or older also should be screened for diabetes. Current American Diabetes Association (ADA) guidelines recommend using glycosylated hemoglobin (A1C), fasting plasma glucose (FPG), or a 2-hour oral glucose tolerance test to screen for diabetes. The ADA guidelines provide diagnostic values for FPG to define prediabetes and diabetes; however, they do not currently offer a diagnostic criterion for random plasma glucose (RPG) to diagnose prediabetes. Fingerstick blood glucose (FSBG) screening alone commonly proves to be inconclusive, as individuals typically have eaten or had sweetened beverages before testing. Nonfasting FSBG results less than 200 mg/dL often are encountered without a definitive interpretation.
Because A1C is a recommended diagnostic criterion for diabetes (in contrast to RPG), point-of-care (POC) A1C may offer an effective alternative to FSBG screening. Other advantages of POC A1C screening include its use in the nonfasting individual and its ability to reflect long-term glycemic control.
In this study, the A1CNow+ POC A1C meter (Bayer, Tarrytown, NY) was used for POC A1C screening. A1C laboratory assay technology typically is based on either charge differences (high-performance liquid chromatography [HPLC]) or structure (boronate affinity or immunoassay combined with general chemistry). These methodologies require trained personnel and time to perform and are expensive. More recently, POC A1C methods have been used to provide rapid results. Although several methods are available, they are typically very expensive and/or difficult to use. The A1CNow+ POC A1C meter is different in that it provides a quick, economical, easy-to-use way of testing A1C. It is a small, portable, inexpensive, semidisposable A1C monitor that has been certified by the National Glycohemoglobin Standardization Program (NGSP), waived under the Clinical Laboratory Improvements Amendments, and cleared by the Food and Drug Administration (FDA) for home use. It uses immunoassay and chemistry technology to measure A1C within 5 minutes. Per correlation analysis using a level 2 NGSP standardized laboratory, this monitor is both precise and accurate relative to HPLC. One monitor is used for 10 test cartridges. After the 10 cartridges have been used, the monitor is disposed; therefore, no calibration is required. Depending on pricing structure, the institutional cost of each test varies. The cost to Carolina Family Health Centers, Inc. (CFHC, Inc.), where this study was performed, was $6 per test.
The 2011 ADA Standards of Medical Care in Diabetes identify Latino individuals as being at high risk for developing diabetes. Because the migrant farm workers of eastern North Carolina are mainly Hispanic and therefore considered a high-risk population, personnel at CFHC, Inc., perform routine health screenings annually in the migrant camps. Many of the workers have little access to routine health care; therefore, the screenings offer a key opportunity to detect undiagnosed diabetes, schedule follow-up testing for diagnosis, and when needed, initiate diabetes care. However, the optimal POC test in such a setting has not been identified.