The effect of fluorescein on the accuracy of blood glucose determination by glucose meters.

Abstract

To investigate whether intravenous fluorescein significantly affected the accuracy of a glucose meter. Thirty-four consecutive patients undergoing fluorescein angiography were recruited. Venous blood was removed immediately before and 1 hour after injection of 5 mls of 20% Sodium Fluorescein solution (1 mg). Whole blood glucose was measured with a glucose meter and plasma glucose levels were measured by the Department of Biochemistry for both samples. The results were analysed using Wilcoxon matched pairs test. Mean glucose results before fluorescein injection were 7.4 mmol/l (SD 4.5) with the glucose meter and 8.1 mmol/l (SD 5.0) biochemically (p=0.02). The post dose levels were 7.2 mmol/l (SD 4.7) and 8.5 mmol/l (SD 4.8), respectively (p=0.001). The difference between the mean results of the two tests was 0.7 mmol/l before fluorescein and 1.3 mmol/l after fluorescein (p=0.001) Intravenous fluorescein appears to influence minimally the difference between glucose levels measured in the laboratory and by glucose meter. The degree of difference, whilst achieving statistical significance, should not affect insulin dosage clinically.