In vitro drug interference with home blood-glucose-measurement systems

The in vitro effects of ascorbic acid, acetaminophen, salicylic acid, and gentisic acid on home blood-glucose-measurement systems were studied. Whole blood in the normoglycemic range was spiked with quantities of each study drug at low, moderate, and high therapeutic concentrations. The glucose concentrations of the blood was measured using Chemstrip bG, Dextrostix, and Visidex II home blood-glucose-monitoring systems. Serum samples were also measured by two automated systems, a glucose-oxidase method and a hexokinase method. Mean values were compared (1) within the same glucose-measurement system to determine the extent of drug interference, and (2) to values obtained by other systems to determine the reliability among systems. Changes between the control and treatment glucose mean concentrations of 20% or more were considered clinically important. Drug interference was observed with all three home blood-glucose-measurement systems and was drug-concentration dependent. Both automated systems were associated with drug interference at the highest concentration of salicyclic acid, and the hexokinase method was influenced at the highest concentration of gentisic acid. No clinically important differences were observed between the automated systems; however, differences were observed between the automated and home blood-glucose-monitoring systems. Salicylic acid, acetaminophen, and ascorbic acid interfere with home blood-glucose-measurement systems. Switching between home blood-glucose-measurement systems could result in a poor assessment of blood-glucose values. In general, the values determined by home and automated systems should not be compared clinically.