New facts have recently enhanced interest in the topic of reference intervals. In particular, the International Organization for Standardization standard 15189, requesting that 'biological reference intervals shall be periodically reviewed', and the directive of the European Union on in vitro diagnostic medical devices asking manufacturers to provide detailed information on reference intervals, have renewed interest in the subject. This review presents an update on the topic, discussing the theoretical aspects and the most critical issues. The basic approach to the definition of reference intervals proposed in the original International Federation of Clinical Chemistry documents still remain valid. The use of data mining to obtain reference data from existing databases has severe limitations. New statistical approaches to discard outliers and to compute reference limits have been recommended. On the other hand, perspectives opened by the improvement in standardization through the implementation of the concept of traceability suggest new models to define 'common' reference intervals that can be transferred and adopted by different clinical laboratories in order to decrease the proliferation of different reference intervals not always justified by differences in population characteristics or in analytical methodology.

High-quality performance of medical devices for glucose monitoring is important for a safe and efficient usage of this diagnostic option by patients with diabetes. The mean absolute relative difference (MARD) parameter is used most often to characterize the measurement performance of systems for continuous glucose monitoring (CGM). Calculation of this parameter is relatively easy and comparison of the MARD numbers between different CGM systems appears to be straightforward on the first glance. However, a closer look reveals that a number of complex aspects make interpretation of the MARD numbers provided by the manufacturer for their CGM systems difficult. In this review, these aspects are discussed and considerations are made for a systematic and appropriate evaluation of the MARD in clinical trials. The MARD should not be used as the sole parameter to characterize CGM systems, especially when it comes to nonadjunctive usage of such systems.

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Self-monitoring of blood glucose (SMBG) both in insulintreated and non-insulin-treated people with diabetes is supported by recently published trials, reviews, meta-analyses, and guidelines. [1][2][3][4][5][6][7] SMBG is recommended to be performed in a structured approach. 2,5,8,9 It is reported to be only useful when blood glucose (BG) data are interpreted and utilized for immediate therapeutic actions. 3,4,[10][11][12][13] For instance, the need for adequate dosing of insulin heavily depends on reliable glucose information. 8 In particular, patients with insulintreated diabetes perform SMBG as a substantial element of daily management of diabetes.14,15 The term "BG system" denotes the combination of a BG meter and test strips, and both determine analytical performance. 8 The analytical and handling performance of BG systems has largely improved over the past decades. In addition, the implementation of inmeter safety features (ie, validity of test strips check) has further increased the safety of these devices. 16 Consequently, patients with appropriate training and a good performance of BG testing can typically rely on the precision of BG measurement results. However, in the daily practice a range of factors with potential impact on the reliability of BG measurement needs to be considered. In fact, this is an important aspect in field of point-of-care (POC) testing. 17 Members of the diabetes team and patients should be well informed about all factors potentially falsifying BG measurement results: human, meter-inherent, test-strip-inherent, environmental, physiological, and medication-related impact factors (Table 1).The risk of misinterpretation of BG readings can be minimized by detailed information on the factors potentially affecting BG measurement. Hence, the aim of this publication is to review the current knowledge on limitations and interferences significant for reliable BG testing.Nonetheless, due to the rapid technological progress, it should be kept in mind that performance of most more recent BG meters may not always be reflected by the reviewed literature, since it reports on data generated with older BG generations. 17 Moreover, it is important to note that some studies on limitations of BG meters were performed under extreme conditions which do not comply with the approved conditions of usage. AbstractIn general, patients with diabetes performing self-monitoring of blood glucose (SMBG) can strongly rely on the accuracy of measurement results. However, various factors such as application errors, extreme environmental conditions, extreme hematocrit values, or medication interferences may potentially falsify blood glucose readings. Incorrect blood glucose readings may lead to treatment errors, for example, incorrect insulin dosing. Therefore, the diabetes team as well as the patients should be well informed about limitations in blood glucose testing. The aim of this publication is to review the current knowledge on limitations and interferences in blood glucose testing with the perspective of the...

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