Reliability of Point-of-Care Capillary Blood Glucose Measurements in the Critical Value Range

Abstract

Context.-Point-of-care glucose (POCG) testing on capillary blood specimens is central to maintaining glycemic control in patients with diabetes. Although there are known performance issues with POCG methods, especially for maintaining tight glucose control, there is little information about the accuracy of results in the critical ranges that may involve life-threatening conditions.Objectives.-To evaluate the reliability of POCG measurements in critical, high (.600 mg/dL) and low (,40 mg/dL) ranges.Design.-One-year retrospective analysis of POCG (ACCU-CHEK glucose meter, Roche Diagnostics Corporation, Indianapolis, Indiana) results for routine patient care were obtained. The frequency and accuracy of repeat testing after critical POCG results was analyzed. A convenience sample of noncritical capillary POCG measurements retested on venous blood specimens by another point-of-care device (RAPIDPoint 405 analyzer, Siemens Medical Solutions USA, Malvern, Pennsylvania) was also evaluated.Results.-Critical values were observed in 2.4 per 1000 POCG tests (256 of 105,928; 0.24%), with the highest rate (76 of 2289; 3.32%) from the emergency department. Twice as many critical high values as critical low values were seen. Nearly 80% of critical POCG tests (204 of 256) were repeated within 10 minutes. Of these 204 repeat measurements, 112 (54.9%) met accuracy criteria (615 mg/dL of low and 620% of high initial values). Accuracy was significantly higher when retesting was performed on the same meter or by the same operator (P .05).Comparison of capillary and venous POCG testing of noncritical results showed no significant difference (P ¼ .95), with 89.8% (125 of 139) meeting accuracy criteria.Conclusions.-POCG measurements in the critical range are frequently erroneous, which is likely caused by preanalytic factors associated with sampling capillary blood. POCG testing practices should include retesting to confirm critical results.(Arch Pathol Lab Med. 2014;138:962-966; doi: 10.5858/ arpa.2013-0455-OA) P oint-of-care glucose (POCG) testing on capillary blood specimens is performed for maintaining glycemic control and for detecting acute hypoglycemic and hyperglycemic conditions. Preanalytic factors, such as hypoxia, anemia, interfering substances, and specimen type, have been shown to affect the accuracy of POCG measurements. [1][2][3][4][5] There is limited information, however, about the reliability of POCG measurements in the critical high and low ranges. That knowledge is important because accurate testing and prompt reporting of critical values is an important patient safety goal. 6A previous study 7 has shown that POCG measurements in critical high and low ranges were frequently erroneous when reevaluated by measuring another capillary or venous blood specimen. However, there is little other information about optimal POCG test performance or practices for accurately detecting critical results. For example, retesting is generally not necessary for checking the accuracy of critical values obtained from clinical laboratory ...

Point-of-Care Glucose Critical Values: A Q-Probes Study Involving 50 Health Care Facilities and 2349 Critical Results

“…Previous studies conducted in single institutions using similar criteria have shown comparable discrepancy rates when critical POCG measurements were repeated. [7][8][9] In comparison, significant error rates for critical glucose measurements performed in 86 clinical laboratories on venous blood specimens was only 0.5% (13 of 2517). 11 Interestingly, rates of repeat testing were not significantly higher among participants with retesting procedures, suggesting that this factor did not affect practice.…”

“…We used 10 minutes as the time limit for retesting because other studies have used 5 to 10 minutes and, in practice, most repeat measurements are completed within the first few minutes. [7][8][9] Additional work is needed to standardize confirmation methods that include optimal time for retesting and criteria used to interpret results. The type of specimen (capillary, venous, or either) specified for retesting varied widely among those with retesting procedures, although in practice, capillary blood was used about 76% of the time.…”

“…A previous study showed that only about 25% of operators encountered a critical POCG result during a 1-year period. 7 Thus, the likelihood of POCG operators measuring a critical result is relatively infrequent compared with that of core laboratory technologists, who manage critical results every day. Thus, it would be expected that most POCG operators would have little experience with critical POCG results.…”

“…Among the few studies involving critical values with POCG methods, all have raised concerns about risks from erroneous measurements. [6][7][8][9] In contrast, glucose or other test results in the critical value range from specimens tested by clinical laboratories are rarely inaccurate. 10,11 These observations have important implications because testing conditions and reliability of point-of-care tests may require different operational and management strategies than those applied to clinical laboratory testing.…”

Utility of point‐of‐care vs reference laboratory testing for the evaluation of glucose levels

“…Over the past few decades, diagnostic technologies have become cheaper, easier to handle, and in some cases more accurate, thus enabling physicians to make informed decisions about treatment, specialty referral and hospital admission [5]. There is a wide range and growing number of point-of-care and handheld devices or portable analysers, which provide rapid 'on-site' glucose levels to help maintain glycaemic control and to detect acute hypoglycaemic and hyperglycaemic conditions [6] through glucose oxidase or glucose 1-dehydrogenase methodology [7]. In addition to their current use by patients, these may have the potential to improve outcomes in primary care by optimizing clinical decisions, reducing referrals, reducing hospitalization time, improving efficiency of care, and decreasing costs [8].…”