The Accuracy of Home Glucose Monitoring Devices during Hypo and Hyperglycaemia
Self – monitoring of blood glucose at home is useful for the management of diabetes as it helps to monitor symptoms of hyper and hypoglycaemia (Diabetes UK). Testing of blood glucose also helps patients to adjust dosages of medication such as insulin and sulphonylureas, monitor the effects of exercise on blood glucose levels, and plan meals (Diabetes UK and Nipro Diagnostics, 2011). The FDA (US- Food and Drug Administration) (2014) refers to a trial in 1993 for control and complications of diabetes which stated “that good glucose control using home monitors led to fewer disease complications”. For these reasons blood glucose meters that aid self- monitoring most be accurate.
Nipro Diagnostics (2011) in the “Accuracy Study of Blood Glucose Monitoring Systems” states that the “use of blood glucose meters and test strips are effective in controlling blood glucose values”. There are currently different brands of meters on the market ranging from expensive to less expensive. The accuracy of meters has been questioned by patients and consumer blog groups such as the” American Association of Retired Persons” and therefore the FDA and MHRA (UK-Medicines Healthcare Products and Regulatory Agency) monitor medical devices to ensure they work safely and provide accurate results. At a worldwide level the ISO (International Organization for Standardization) provide standards and regulations which manufactures must meet when producing self-monitoring glucose meters. All brands of glucose meters are subject to the ISO standards (Nipro Diagnostics, 2011)
Incorrect blood glucose readings may occur with blood glucose meters due to software issues but may also occur due to operator errors, effects of oxidized uric acid and abnormal haematocrit levels (ADDE, 2013, Bode, 2007, and FDA, 2014).
Inaccuracies due to operator error or short cuts, maybe due to poor technique, use of expired test strips, the use of un – calibrated meters, or meters calibrated with expired control solutions, unwashed hands before testing, applying too much or too little blood to the test strip, testing from sites damp with alcohol and from meters and testing strips not stored and handled according to manufacturer’s instructions (ADDE, 2013 Bode, 2007, and FDA, 2014).
Oxidised uric acid may lead to falsely low glucose levels by the home glucose meter (Bode, 2007). Dehydration causes haematocrit levels to be elevated resulting in low glucose reading, whereas, high levels caused by anemia, for example, cause low levels of haematocrit resulting in high glucose readings (Bode, 2007).
In 2013 the ISO updated the ISO 15197:2003 standards for the “self – testing glucose monitoring Systems” (ISO 15197:2013). The improved standards will enhance even greater accuracy for glucose meters for patient use (ISO, 2013). In 2013 a meeting of the Diabetes Technology Society researchers, presented evidence from studies done in the USA and Germany concerning accuracy of blood glucose meters using the ISO 15197:2003 standards (ADDE, 2013). The evidence presented showed that many meters did not meet the ISO standard that requires 95% of results to be within range of +/- 20% of the true value (ADDE, 2013). The new international standards ISO 15197:2013 require meters have increased accuracy especially with glucose reading over 4.2mmol/l, and 99% of all results to be within ±15% of true value (ISO, 2013).
The FDA (2010) report as cited on Diabetesnet.com says that a potential inaccuracy with glucose meters between 1992 to 2009 were associated with 100 deaths and 12,672 injuries from 2004 to 2008. American Diabetes Association reported that up to 50% of home glucose meters did not meet the ±20% of the true values (Alto et al, 2002).
The MHRA in April 2013 issued a Medical Device Alert (MDA/2013/022) about “Home Use Blood Glucose Meters”. These meters were recalled due to a software fault. At very high glucose concentration patients were given a “falsely low reading with One Touch Verio Pro and no results were recorded with One Touch Verio IQ”. A recent alert (MDA/2014/009) was issued from the MHRA March 2014 about “FreeStyle Mini® and FreeStyle® blood glucose meters”. The meters were recalled because they may be “reporting incorrect low blood glucose reading” (MHRA).
Alto et al (2002) in a study of 111 patients using 21 different brands of meters found that 84% were within the ±20% of the true value even though patients took short cuts. The study highlighted that patients were not always calibrating meters due to the price of strips and the use of expired control solutions (Alto et al, 2002). Overall, the blood glucose values obtained in this study were clinically useful (Alto et al, 2002). On the other hand, another study “The accuracy of home glucose meters in hypoglycemia” concluded that some meters were inaccurate in reporting hypoglycaemia (Aydoqdu et al, 2010).
There is evidence that home glucose meters are associated with inaccuracies. These inaccuracies maybe due to software problems associated with the meters or due to the operator. The operator plays a very important role in the accuracy of home glucose monitoring. The operator should follow the manufacturer advice about use, technique, storage and calibration of meters to achieve optimum results. Diabetes UK (2014) and the FDA (2014) encourage patients to check accuracy of home glucose meters by comparing to results of blood processed in a laboratory (Collazo – Clavell, 2012). ISO has tightened requirements in 2013 for home glucose meters to ensure higher accuracy for all new meters.
Diabetes UK (2014)– “Blood Glucose Meter Guide” [Online]. Available at: http://www.diabetes.org.uk/ (Accessed 23 March 2014)
FDA (2014) – US Food and Drug Administration, ‘Medical Devices’, Blood Glucose Monitoring Devices’. [Online]. Available at: http://www.fda.gov/ (Accessed 23 March 2014)
Nipro Diagnostics (2011) “Accuracy Study of Blood Glucose Monitoring Systems” http://www.niprodiagnostics.com/ (Accessed 23 March 2014)
Bode, B.W, (2007) “The Accuracy and Interferences in Self-monitoring of Blood Glucose”, Blood Glucose monitoring, US Endocrine Disease, pp. 46 -48. [Online]. Available at: http://www.touchendocrinology.com/ (Accessed 30 March 2014)
MHRA (2013) ‘Medical Devices Alert’ Home use blood glucose meters: Lifescan OneTouch Verio Pro; Lifescan OneTouch Verio IQ (MDA/2013/022 [online]. Available at: http://www.mhra.gov.uk/ (Accessed 23 March 2014)
MHRA(2014) ‘Medical Device Alert’ FreeStyle Mini® and FreeStyle® blood glucose monitoring systems manufactured by Abbott Diabetes Care (MDA/2014/009)[Online].Available at: http://www.mhra.gov.uk/ (Accessed 24 March 2014)
ISO (2013) “More accurate self-testing results for diabetes patients with new ISO standard” [Online]. Available at: http://www.iso.org/ (Accessed 23 March 2014)
AADE (2013) ‘American Association of Diabetes Educators’ Practice Advisory Blood Glucose Meter Accuracy [Online. Available at: http://www.diabeteseducator.org/ (Accessed 24 March 2014)
Alto, W.A., Bryson, P, Kindig, J, Meyer, D, and Schneid. J (2002) ‘Assuring the Accuracy of Home Glucose Monitoring’, Journal of the American Board of Family Medicine 15(1). [Online]. Available at: http://www.medscape.com/ (Accessed 30 March 2014)
Aydoqdu, A, Erbil, M.K, Kilic, S, Kutlin, M, Serdar, M, Sonmez, A, Tapan, S, Taslipinar, A, Uckaya, S, Yazici, M, Yilmaz, M.I, and Yilmaz, Z (2010) ‘The accuracy of home glucose meters in hypoglycemia’ Diabetes Technol Ther 12(8), pp. 619-26. PubMed. [Online]. Available at: http://www.ncbi.nlm.nih.gov/ (Accessed 30 March 2014)
Collazo – Clavell, M (2012) ‘Diseases and Conditions’, Sometimes my blood glucose monitor seems to give incorrect readings. What can I do to make sure the measurement is accurate? Mayo Clinic [Online]. Available at: http://www.mayoclinic.org/ (Accessed 30 March 2014)