Factors Affecting Accuracy of Results from Blood Glucose Monitoring

 

Methodologies include in enzymatic methods: glucose oxidase, glucose dehydrogenase or glucose hexokinase.

 

Factors that can degrade the reagent strips:

(1) prolonged exposure to light or air

(2) exposure to excessive humidity

(3) exposure of temperature extremes (too hot, freezing)

(4) exposure to bleach affects some strips (glucose oxidase)

 

The strips should be kept in the original vial with cap closed and the temperature kept below 30°C (86°F) and kept away from all chemicals.

 

Factors affecting the blood sample:

(1) A hematocrit < 35% are associated with falsely low while a hematocrit > 55% is associated with a falsely high value.

(2) severe dehydration may result in falsely low values

(3) use of fluoride as a preservative for the blood specimen will give falsely low values

(4) contamination of hands and fingers with sugar.

(5) whole blood gives results 12-15% less than serum or plasma, while arterial blood has higher values than venous

(6) gross lipemia may affect some methods

(7) high levels of ascorbic acid, acetaminophen or other drugs may give falsely low values while other drugs may give falsely high values

(8) hyperglycemic, hyperosmolar states with or without ketosis may give falsely low values

 

The hands should be washed with warm soapy water, then rinsed and dried before testing.

 

Factors affecting the glucose reading:

(1) Glucose readings may not be linear at extreme values (below 50 mg/dL or above 250 mg/dL). These values should be verified by a regular blood glucose test.

(2) Some monitors may be affected if used next to a cellular phone, radio transmitting device, microwave oven or other source of electromagnetic interference.

(3) Readings at high altitudes may be inaccurate due to reduced oxygen tension.

(4) A color blind person may not be able to read a color change within the spectrum affected by the color blindness.

(5) Competency of the person performing the test (no test is fool proof). Most problems can be corrected by proper training and attention to detail. Periodic proficiency testing can help identify problems with the instrument and/or user.

(6) A control should be run according to the manufacturer's instructions.

 

Factors affecting the instrument:

(1) proper maintenance and cleaning

(2) functional/working batteries

(3) proper storage and protection from damage