title: Reliability of point-of-care capillary blood glucose measurements in the critical value range.
abstract: BACKGROUND
  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.
  
  
  OBJECTIVE
  To evaluate the reliability of POCG measurements in critical, high (>600 mg/dL) and low (<40 mg/dL) ranges.
  
  
  METHODS
  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 (±15 mg/dL of low and ±20% 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 = .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.
authors: From the Department of Pathology and Laboratory Medicine, Southern Arizona VA Healthcare System (Drs Schifman, Nguyen, Ms Page), and the Department of Pathology, University of Arizona (Drs Schifman, Nguyen).
authors: Ron B
authors: RB
authors: Schifman
authors: Tan T
authors: TT
authors: Nguyen
authors: Susan T
authors: ST
authors: Page
mesh_terms: D000208:Acute Disease; D001774:Blood Chemical Analysis / Q000295:instrumentation* / Q000592:standards / Q000706:statistics & numerical data; D001786:Blood Glucose / Q000032:analysis*; D060166:Capillary Tubing; D016638:Critical Illness; D048909:Diabetes Complications / Q000097:blood / Q000175:diagnosis; D003920:Diabetes Mellitus / Q000097:blood; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000175:diagnosis; D007003:Hypoglycemia / Q000097:blood / Q000175:diagnosis; D019095:Point-of-Care Systems / Q000592:standards / Q000706:statistics & numerical data*; D011786:Quality Control; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D001786:Blood Glucose