Conditions That Can Adversely Affect SMBG Results

Conditions That Can Adversely Affect SMBG Results

Condition	Outcome
Patient has poor hygiene.	Failure to wash hands before testing or keep the meter clean can commonly cause errors18 as well as potential contamination.10
Test strips are not specific to the meter in which they are used.	A mismatch between meter and strips will produce inaccurate results.10
The expiry date on the test strips has passed.	Outdated test strips can produce inaccurate results.10
Test strips are exposed to humidity, high temperatures, or strong light; test strip container is left open.	Humidity and high temperatures can deteriorate the enzyme on the test strip that interacts with glucose to produce the result, producing a falsely elevated number.19
Test is done at high altitude.	Can adversely affect results, particularly in low temperatures.20
Patient does not assess accuracy of new meter or test strip batch using control solution.	The patient should test each new meter and each new package of test strips with control solution. Prescriptions should include control solutions as well as meters and strips.10
Patient does not properly calibrate meter as required.	Patients must properly calibrate their meters for each new set of test strips.10 Coding errors can produce inaccurate results that can in turn lead to insulin dosing errors.21 Alternatively, patients can be advised to choose meters with automatic calibration, which significantly reduces the possibility for these types of errors.21
Patient has variable hematocrit levels (eg, smokers, patients living at high altitudes, dehydrated patients, or patients with sickle-cell anemia, polycythemia, or end-stage renal failure).15	Abnormally high hematocrit can artificially depress the glucose result; abnormally low hematocrit levels can artificially elevate the glucose result22; this occurs because the higher concentration of red blood cells blocks the plasma from adequately diffusing through the strip layers.10
Patient is receiving a treatment containing a sugar (eg, xylose, maltose, icodextrin, galactose).	Test strips that use the enzyme glucose dehydrogenase pyrroloquinolinequinone or glucose-oxireductase can give falsely elevated readings in patients who are also receiving treatments containing other sugars.23 In rare instances, this has caused death and has been the subject of an FDA warning.24 Not all glucose meters use this enzyme, and the test method used is identified in the package insert for the glucose strips.
Patient is taking acetaminophen, ibuprofen, ascorbic acid, dopamine, L-dopa, methyl dopa, tetracycline, ephedrine.	These substances (among others) can potentially influence the reliability of blood glucose test results.10