Comparison of Glucose Point-of-Care Values With Laboratory Values in Critically Ill Patients

Shearer, Anna RN
Boehmer, Marilyn RN, BA, CCRN
Closs, Melanie RN, BSN
Dela Rosa, Rosalina RN, BSN, CCRN
Hamilton, Jean RN, CCRN
Horton, Karen RN, BSN
McGrath, Rose RN
Schulman, Christine RN, MS, CNS, CCRN

About the Authors
Anna Shearer, Marilyn Boehmer, Melanie Closs, Rosalina Dela Rosa, Jean Hamilton, Karen Horton, and Rose McGrath are staff nurses in the intensive care unit at Providence St Vincent's Medical Center, Portland, Oregon. Christine Schulman is a clinical nurse specialist and consultant in Portland, Oregon.

Corresponding author: Anna Shearer, RN, Intensive Care Unit, Providence Saint Vincent's Medical Center, 9205 SW Barnes Rd, Portland, OR 97225 (e-mail: [email protected]).

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FINANCIAL DISCLOSURES None reported.

American Journal of Critical Care 18(3):p 224-230, May 2009. | DOI: 10.4037/ajcc2009448

Background

Blood from central venous or arterial catheters as well as from fingersticks is often used for point-of-care glucose testing.

Objectives

To compare glucose values obtained with a pointof-care device for catheter and fingerstick blood samples with values obtained by clinical laboratory analysis of a catheter blood sample.

Methods

A method-comparison design was used. Point-of-care values for fingerstick and catheter blood samples were compared with laboratory values for blood from catheters in a convenience sample of 63 critically ill patients. Device bias and precision were calculated and graphed according to the Bland-Altman method, and a t test was used to determine differences in glucose values for the 2 methods.

Results

Laboratory glucose values for blood from a catheter sample differed significantly from point-of-care values for blood from a fingerstick (t_1,61 = 5.01; P < .001) and from a catheter (t_1,61 = 3.91; P < .001). Bias and precision for the pointof-care device was large (fingerstick, 8.7 and 13.7; catheter, 7.0 and 14.0); 20% of the values differed from the laboratory glucose values by more than 20 mg/dL. Point-of-care glucose values for fingerstick and catheter samples did not differ (P = .41).

Conclusions

Glucose values obtained with a point-of-care device differ significantly from those obtained by laboratory analysis. The magnitude of these differences calls into question the widespread practice of using point-of-care glucose testing to guide insulin titration for tight glucose control. Errors in dosing could easily be made because of the large bias and precision associated with a point-of-care device. (American Journal of Critical Care. 2009;18:224–230)