Precision and accuracy: comparison of point-of-care and laboratory glucose concentrations in cardiothoracic surgery patients.
BACKGROUND
There have been variable results on the practice of tight glycemic control, and studies have demonstrated that point-of-care (POC) glucometers have variable accuracy.


OBJECTIVE
The purpose of this study was to determine the difference between blood glucose concentrations obtained from POC glucometers as compared with laboratory results in cardiothoracic surgery (CTS) patients.


METHODS
This was a descriptive study on a convenience sample of 46 CTS patients. A single sample of arterial blood was collected and analyzed at the bedside with the POC glucometer and in the laboratory to obtain a serum glucose concentration and hematocrit (Hct). A paired t test was used to compare the mean differences along with Spearman ρ correlation to examine the relationship between difference scores and Hct.


RESULTS
The POC glucose was significantly higher than the laboratory result (t = 8.5, P < .001) with a mean of 12.3 (SD, 9.8) mg/dL. Spearman ρ correlation between the difference scores and Hct was -0.43, P = .003. Using a tercile split, groups with Hct of less than 26% (n = 16) and greater than 29% (n = 15) were identified. The unpaired t test on the mean difference scores of these 2 groups was t = -2.7, P < .01, with an overall mean difference 8.6 mg/dL (95% confidence interval, -15 to -2.2). The mean difference was 16.3 in the low-Hct group and 7.8 in the high-Hct group.


CONCLUSIONS
Point-of-care glucometer results differ significantly from laboratory glucose concentrations, with the difference widening as the Hct decreases. This raises the concern about using POC devices to provide tight glycemic control in CTS patients.
Cardiac and Surgical Intensive Care Unit at Oregon Health & Science University, Portland, Oregon 97239, USA. denfeldq@ohsu.edu
Quin E
QE
Denfeld
Teresa T
TT
Goodell
Kelly N
KN
Stafford
Steve
S
Kazmierczak
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001786:Blood Glucose / Q000032:analysis*; D006348:Cardiac Surgical Procedures; D019411:Clinical Laboratory Techniques; D016638:Critical Illness; D005260:Female; D006400:Hematocrit; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011182:Postoperative Care; D012494:Sampling Studies
D001786:Blood Glucose