Accuracy and precision of four main glucometers used in a Sub-Saharan African Country: a cross-sectional study

Introduction capillary glucose measurement using point-of-care glucometers is an essential part of diabetes care. We determined the technical accuracy, clinical accuracy and precision of commonly available glucometers against standard spectrophotometry in Cameroon. Methods a sample of four glucometers was selected. In the 108 diabetic and non-diabetic participants, blood glucose values obtained by glucometers were compared to the reference laboratory method to determine their technical and clinical accuracies. Precision was determined by repeated measurements using standard solutions of different concentrations. Results accu-Chek® Active, CodeFree™, Mylife™ Pura™ and OneTouch® Ultra® 2 values had correlation coefficients of 0.96, 0.87, 0.97 and 0.94 respectively with reference values, and biases of 18.7%, 29.1%, 16.1% and 13.8% respectively. All glucometers had ≥ 95% of values located within the confidence limits except OneTouch® Ultra®2. Accu-Chek® Active, CodeFree™, Mylife™ Pura™ and OneTouch® Ultra® 2 had 99%, 93.1%, 100% and 98.0% of values in Parke's zones A and B. The coefficients of variation of the glucometers were all below 5% at all standard concentrations, except for Accu-Chek® Active for glucose concentrations at100 and 200mg/dL. Conclusion no glucometer met all the international recommendations for technical accuracy. Accu-Chek™ Active and Mylife™, Pura™ met the International Organization for Standardization 2013 recommendations for clinical accuracy based on Parke's consensus error grid analysis. All glucometers assessed except Accu-Chek® Active showed a satisfactory level of precision at all concentrations of standard solutions used.


Introduction
The growing diabetes epidemics worldwide and in sub-Saharan Africa (SSA) poses diagnostic and management challenges [1]. Selfmeasurement and monitoring of blood glucose (SMBG) using pointof-care (POC) glucometers is an essential component of diabetic management and follow-up [2]. There is strong evidence that rigorous glycaemic control can in the long-run cost-effectively reduce the complications associated with type 2 diabetes [3]. The American Diabetes Association (ADA) recommends and promotes SMBG using glucometers in order to allow patients living with diabetes to achieve and maintain desired glycaemic targets [4]. Glucometers are very useful in timely diagnosis of acute diabetes complications, especially hypoglycaemia and hyperglycaemia which can contribute to higher morbidity and mortality [5]. Owing to the wide acceptance and use of POC glucometers in different settings, there is a competition-driven development by manufacturers in both meter and test strips technology. These innovations have allowed for greater reliability of results when compared to the reference laboratory method.
Nonetheless, there are differences in performance across these monitoring devices. These have prompted the need to develop standard performance guidelines to guide manufacturers on the minimum requirements for these glucometers [6][7][8] and this shall apply to at least 95% of results [6]. Many recent studies have highlighted the limitations of most glucometers in meeting these recommendations [9][10][11], very few of which were carried out in SSA [12]. Because of limited resources in most SSA countries,  [13]. This was compared to the American Diabetes Association (ADA) standard of a bias of < 5% being acceptable [14,15]. The agreement between the two measurements (that is, the glucometer and reference readings) at any given level was then examined using Bland-Altman plots [16]. Glycaemic values were also evaluated in the and 0% in other zones. The precision of glucometers was determined by the calculation of the coefficients of variation (CV) that was further compared to the ISO criteria. The CV was computed as the standard deviation divided by the mean and expressed as a percentage [13].
A CV of less than 5% was considered as being precise [19].  Pura™ yielded the highest proportion within the two ranges (Table 3).  CodeFree TM , because they may result in the use of higher doses of hypoglycaemic agents. Also, the glucometers may fail to identify hypoglycaemia due to overestimation of blood glucose levels.

Clinical accuracy of glucometers
Regarding the statistically significant difference between women and men in the correlation between reference values and values provided by all glucometers, we speculate that they may be due to the influence of body creams and lotions used by Cameroonian women, which may contain contaminants that interact with capillary glucose measurement [26]. The following potential limitations of our study should be considered when interpreting and generalizing our findings.
Firstly, ISO recommendations were meant for self-testing. Hence, the assessment of the accuracy by a medically trained person can potentially overestimate the accuracy of the glucometers when compared to self-testing. Secondly, although all participants carefully washed their hands before capillary glucose measurement, all potential interferences to glucometer readings may not have been eliminated. Also, the investigator performing capillary glucose measurements was not blinded to the meter being used.
Nevertheless, the reference values were made available only after the completion of all glucometer-based glucose determination. Finally, measurements in the hypoglycaemic range could not be carried out; hence, performance of the glucometers could not be assessed at all glycaemic ranges. Despite these potential limitations and unlike other studies that have been carried out on glucometers, we used very exhaustive analytical methods and endeavoured to compare the findings of our study to recommendations of more than one international body.

Conclusion
In conclusion, based on the extensive comparisons conducted in this study, no glucometer met all the required international  Failure of glucometers to comply with the norms will lead to erroneous management of diabetic patients.

What this study adds
 This study is one of the first of its kind in Cameroon that seeks to determine the accuracy and precision of four commonly used glucometers in Cameroon when compared to reference laboratory method;  This study gives suggestions based on our results for which glucometers might be better for Cameroon.

Competing interests
The authors declare no competing interests.

Authors' contributions
Simeon-Pierre Choukem: conception and design of the study, data collection, data interpretation, drafting and review of the manuscript.        OneTouch ® Ultra ® 2) and the reference method, glucometer values minus reference value for each participant (y-axis) is plotted against the mean of the two measurements (x-axis) and are represented by the black dots; the horizontal doted blue line through zero is the line of perfect agreement between the two measurements; the parallel solid black line is the mean bias; the green colour band around the solid black line is the standard error around the mean bias estimates, while the shaded area represents the 95% confidence intervals; the linear curve of best fit is also shown (broken oblique blue line) OneTouch ® Ultra ® 2), Zone A: results given by the glucometer are clinically accurate within+/-20% of the reference; zone B: the error of the results given by the glucometer is above 20%, but would lead to minor or no treatment error; zone C: results given by the glucometer would begin to lead to treatment decisions opposite to that called for by the real blood glucose levels; zone D: results given by the glucometer lead to a failure to detect and treat errors; zone E: results given by the glucometer lead to erroneous treatment of hypo or hyperglycemia