Factors affecting accuracy and the importance of interference testing

Performance standards organisations, such as the Clinical and Laboratory Standards Institute (CLSI), the Food and Drug Administration (FDA), the International Organization for Standardization (ISO), and the Medicines & Healthcare products Regulatory Agency (MHRA), stipulate requirements to improve meter system accuracy (EN ISO 15197:2013) and ensure people with diabetes get the most precise measurements possible¹. Many factors, including patient errors and interfering medicines used to treat comorbidities, can also affect accuracy.

Patient use and handling factors

Patients must follow the proper pre-check steps and take care of their blood glucose monitoring supplies. Consider the following talking points to help your patients understand and avoid common interference factors:

• Environment: Patients should be aware that some temperature extremes, altitude and humidity can affect blood glucose meter accuracy.
• Clean hands: The testing area must be thoroughly cleaned - advise patients to remove anything from their skin that contains glucose, such as fruit residue or body lotion, or even trace amounts of a chocolate bar they just ate².
• Storage: When patients remove a test strip from the vial, it is important they make sure the vial is tightly closed. Properly storing testing supplies is even more important as newer meters use smaller testing samples. Keep in mind that testing supplies, which are subject to expiration after opening, must be stored in a dry place and in accordance with the temperature ranges indicated on the manufacturer's instructions³.

Analytical factors

Some factors can interfere with the analysis itself:

• Environmental conditions: High altitude, temperature, and humidity all affect blood glucose meter accuracy. In fact, research shows elevation can prompt a 1 to 2 percent underestimation of blood glucose⁴. Additionally, a patient’s individual haematocrit range (which is also sensitive to high altitudes) impacts reading precision. Patients should refer to product labels for details on meter performance under varying environmental conditions³.
• Interfering substances: In some instances, medications or food affect testing accuracy. Patients taking paracetamol or eating foods containing maltose or high levels of vitamin C (ascorbic acid) may obtain false hyperglycaemia results³.

Additionally, while the performance standards organisations mentioned above require blood glucose meter manufacturers to test for the impact of 24 different interfering substances, many current therapeutic approaches are not included⁵. One substance that manufacturers do not have to test for is sodium-glucose transport protein 2 (SGLT2). Since 2012, a number of SGLT2 inhibitors have come to market for use in diabetes therapy⁵.

A study investigating the performance of the Accu-Chek blood glucose monitoring systems (Accu-Chek Active, Accu-Chek Aviva, Accu-Chek Guide, Accu-Chek Instant, and Accu-Chek Performa) looked specifically at patients taking one of four SGLT2-inhibtors⁶.

• Canagliflozin (Invokana^®)
• Dapagliflozin (Farxiga^®)
• Empagliflozin (Jardiance^®)
• Ertugliflozin (Steglatro^®)

The results indicated that, based on the acceptable deviation requirements, none of these medications interfered with the performance of the Accu-Chek blood glucose monitoring systems.

Furthermore, Roche ensures detailed interference testing in Accu-Chek blood glucose meters of over 200 substances^6,7, including:

• Substances for high blood pressure such as Ramipril & HCT
• Substances for lipid metabolic disorder such as Atorvastatin
• Substances for uric acid disorder such as Allopurinol.

Reliable measurements are the basis of successful diabetes therapy. With Accu-Chek blood glucose monitoring systems, you can feel confident that patients, including those with type 2 diabetes taking SGLT2-inhibitors, can safely and accurately measure their blood glucose with a reliable meter⁶.