Glucometer analysis of one-hour glucose challenge samples

Objective: Our purpose was to explore a cost-saving measure for diabetes screening by using glucometer testing on venous whole blood obtained after a 1-hour glucose challenge test. Glucometer results falling above an upper threshold would predict abnormal plasma values and mandate a glucose tolerance test; results below the lower threshold would predict normal plasma values and avoid further testing. Results between the thresholds would require traditional plasma analysis. Study Design: We performed a prospective cohort study on 222 consecutive pregnant women. A standard 50 gm glucose screen was performed with venous blood drawn at 1 hour. We immediately removed a drop of whole blood from the venous sample and analyzed it on a portable glucometer, Accu-Chek III. The remaining sample was submitted immediately for routine plasma analysis. All values were obtained on the same glucometer, which was calibrated daily in our clinic laboratory. Regression analysis was performed on 129 samples to select the two thresholds. The selected thresholds were then applied prospectively to the next 93 consecutive samples for validation. Results: Excellent correlation (r = 0.9045) exists between the glucometer and laboratory values. Glucometer threshold values of 110 mg/dl and 155 mg/dl were selected because they predicted plasma values <135 mg/dl or >135 mg/dl with 95% certainty, respectively. Prospectively, the thresholds were completely accurate in classifying the values. Conclusion: Venous whole blood assayed by glucometer can reliably predict an elevated or normal automated plasma glucose value. By applying thresholds, three fourths of all patients can immediately receive reassuring information, whereas the patients with poorest glucose tolerance are immediately identified and diagnostic testing is scheduled. Additionally, our model reduces the number of automated laboratory studies by 80% and reduces the cost of diabetic screening.