Effect of Adverse Storage Conditions on Performance of Glucometer Test Strips

Abstract

OBJECTIVE: A study was conducted to assess the impact of adverse storage environments, i.e., not manufacturer recommended, on the performance of reagent test strips used with a point of care testing (POCT) glucometer to measure whole blood glucose levels.

DESIGN/SETTING: Glucose reagent test strips were placed in open, i.e., uncapped, and closed, i.e., capped vials. These vials were those used by the manufacturer to package and store the reagent test strips. One of each type of vial was placed in the manufacturer-recommended storage environment at room temperature and the adverse environments (incubator, direct light to mimic sunlight exposure, humidity, and refrigerated). The Accu-Chek Easy® glucometer and reagent test strips as well as Accu-Chek Easy high and low glucose control solutions, manufactured by Roche, were used for this study.

MAIN OUTCOME MEASURES: On day-3, day-7, and then once every 7 days, one strip from each vial in each environment was tested with the same glucometer using both a high and a low glucose control. The strip was considered failed for a type of vial and storage environment when either control was out of the reference range on a regular testing day and still out of range when tested the subsequent day. Testing continued up to 50 days.

RESULTS: For the tested environments it was found that, overall, test strip stability lasted longer for closed vials than open vials. For open vials in adverse storage conditions, the refrigerator environment offered the longest stability at 35 to 50 days and direct light and humidity offered the shortest periods of stability at 3 to 14 days.

CONCLUSIONS: The results of this study support the manufacturer's recommendations to store POCT glucose test strips in their original vial, capped, and at room temperature, though refrigeration may offer an alternative storage environment with acceptable stability. As compliance with testing, quality control, and storage instructions is often an issue with POCT, the manufacturers of these systems for blood glucose measurement should design storage systems that allow the patient to store the glucose meter and the reagent strips in the same location. Manufacturers may also need to consider designing storage systems that are more portable, knowing that patients must take the glucose meters and test strips with them when they travel. Roche's Accu-Chek Compact system is an example of such a design. The glucose test strips are incorporated into a drum that is stored in the Accu-Chek meter itself. When a patient performs a fingerstick blood glucose measurement, the drum advances to move a test strip outside the meter. When the test is complete, the test strip is ejected for disposal.¹

Future studies to clarify the effect of adverse storage conditions, particularly refrigeration, on the integrity of POCT test systems and reagent strips is warranted with currently marketed brands.

ABBREVIATIONS: CLS = clinical laboratory science; CV = coefficient of variation; POCT = point of care testing; SD = standard deviation; μL = microliter.