Table 2.

Effect of Exogenous and Endogenous Interfering Substances on Test Strip Results²⁵

Interfering substance	Therapeutic or reference range, mg/dl	Bias at maximum therapeutic concentration or upper reference value	Limiting con-centration,a mg/dl
Acetaminophen	1.0 to 2.0	≤±1%	35
Ascorbic acidb,c	0.4 to 2.0	≤±1%	10
Bilirubinb	0.3 to 1.2	≤±1%	54
Caffeine	0.5 to 2.0	≤±1%	7
Cholesterolb	150 to 300	≤±1%	1168
Creatinine hydrochloride	0.8 to 1.7	≤±1%	34
Dopamine hydrochloride	0.04	≤±1%	4
Ephedrine	0.005 to 0.01	≤±1%	11
Galactose	5.0	≤±1%	336
Glutathione	0.11	≤±1%	17
Hemoglobin	0.1 to 0.2 (g/dl)	≤±1%	2 (g/dl)
Ibuprofen	1.7 to 7.8	≤±1%	56
Icodextrin	0.5 (g/dl)	≤±1%	2 (g/dl)
L-Dopa	0.02 to 0.3	≤±1%	5
Maltose	120	≤±1%	336
Methyldopa	0.1 to 0.75	≤±1%	3
Sodium gentisate	0.2 to 0.7	≤±1%	112
Sodium salicylate	11.5 to 34.7	≤±1%	112
Tetracycline	0.2 to 0.5	≤±1%	4
Tolaz ami de	3.0	≤±1%	112
Tolbutamide	5.4 to 10.8	≤±1%	112
Triglyceridesb	190	≤±1%	4709
Uric acidb	2.5 to 8.0	≤±1%	59
Xylose	57	51%	6

^aThe concentration of the interfering substance resulting in a ±10% bias of test results as determined by interpolation using linear regression analysis. If a substance did not have a concentration that created a ±10% bias, then the limiting concentration is listed as the highest level tested.

^bAscorbic acid, bilirubin, cholesterol, triglycerides, and uric acid occur naturally in the body, so the effect at the limiting concentration was calculated with respect to the normal concentration rather than 0 mg/dl.

^cAt five times the maximum therapeutic concentration, results showed a 10% assay bias at 80 mg/dl plasma glucose.