Effects of different hematocrit levels on glucose measurements with handheld meters for point-of-care testing.

OBJECTIVES To determine the effects of low, normal, and high hematocrit levels on glucose meter measurements and to assess the clinical risks of hematocrit errors. DESIGN Changes in glucose measurements between low and high hematocrit levels were calculated to determine hematocrit effects. The differences between glucose measured with meters and with a plasma glucose method (YSI 2300) also were compared. SETTING Six hand-held glucose meters were assessed in vitro at low (19.1%), normal (38.5%), and high (58.3%) hematocrit levels, and at 6 glucose concentrations ranging from 2.06 mmol/L (37.1 mg/dL) to 30.24 mmol/L (544.7 mg/dL). RESULTS Most systems, regardless of the reference to which they were calibrated, demonstrated positive bias at lower hematocrit levels and negative bias at higher hematocrit levels. Low, normal, and high hematocrit levels progressively lowered Precision G and Precision QID glucose measurements. Hematocrit effects on the other systems were more dependent on the glucose concentration. Overall, Accu-Chek Comfort Curve showed the least sensitivity to hematocrit changes, except at the lowest glucose concentration. CONCLUSIONS We strongly recommend that clinical professionals choose glucose systems carefully and interpret glucose measurements with extreme caution when the patient's hematocrit value changes, particularly if there is a simultaneous change in glucose level.