Difference in Glucose Values Obtained from Point of Care Glucose Meters and Laboratory Analysis in Critically Ill Patients

ABSTRACT

By Anjannette Cook, RN, BSN, Delyla Laughlin, RN, Margery Moore, RN, BSN, Doreen North, RN, Kathleen Wilkins, RN, BA, BSN, Gay Wong, RN, BSN, Allyson Wallace-Scroggs, RN, MSc, and Lisa Halvorsen, RN, PhD, APRN-BC.

Background Blood for glucose analysis is often obtained interchangeably from indwelling catheters and fingersticks.

Objectives To determine the level of agreement between glucose values obtained by laboratory analysis and with a pointof-care device for blood from 2 different sources: fingerstick and a central venous catheter.

Methods A method-comparison design was used. Point-of-care values for blood from fingersticks and catheters were compared with laboratory values for blood from catheters in a convenience sample of 67 critically ill patients. The effects of hematocrit level and finger edema on differences in glucose values between the

2 methods were also evaluated. A t test was used to determine differences in glucose values obtained via the 2 methods. Differences and limits of agreement were also calculated.

Results Laboratory glucose values for blood from a catheter differed significantly from point-of-care values for blood from the catheter (t1,66 = -9.18; P < .001) and from a fingerstick (t1,66 =6.53; P < .001). Glucose values for the 2 methods differed by 20mg/dL or more for 1 of 6 patients (15%) for catheter samples and for 1 of 5 (21%) for fingerstick samples. Point-of-care glucose values for fingerstick and catheter samples did not differ (P = .98). Hematocrit level significantly explained the difference in glucose values between the 2 methods for both catheter (R2 = 0.288;

P < .001) and fingerstick (R2 = 0.280; P = .02) samples.

Conclusions Use of a commonly used point-of-care device when precise glucose values are needed may lead to faulty treatment decisions. (American Journal of Critical Care. 2009;18:65-72)

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