Case Study

4 downloads 172 Views 487KB Size Report
Physical Examination: The patient had cachexia and obtundation, with multiple decubitus ulcers, dry mucous membranes, and discolored cold fingers. His rectal ...
Case Study Discrepant Glucose Results between Capillary and Venous Blood in an 83-Year-Old White Man Lauren M. Mika, RN, BSN, CEN,1 Maria K. Guyette, MD, MPPM,1,2 Gina Pillage, BS, MT, CHT,4 Kenichi Tamama, MD, PhD3,4,5,* Lab Med Fall 2014;45:e156-e157 DOI: 10.1309/LMT5E3T4VRUNFLCS

ABSTRACT Herein, we present a case of pseudohypoglycemia induced by hypothermia in an 83-year-old white man in whom glucose levels between venous and capillary blood were discrepant. Although pseudohypoglycemia has been reported in the literature, it is underrecognized among health care professionals and laboratorians. Health care professionals may encounter pseudohypoglycemia using glucose meters; the potentially inaccuracy of glucose meter results for critically ill patients has been intensely debated recently. Thus, this article should be educational for the point-of-care community. Keywords: glucose, glucose meter, capillary blood, hypothermia, Raynaud phenomenon, pseudohypoglycemia

Clinical History Patient: 83-year-old white man.

History of Present Illness: The patient was brought into the Emergency Department due to altered mental status and poor oral intake. Past Medical History: Dementia. Physical Examination: The patient had cachexia and obtundation, with multiple decubitus ulcers, dry mucous membranes, and discolored cold fingers. His rectal temperature was 34.0°C. Principle Laboratory Findings: Initially, we noted discrepant glucose levels between capillary and venous blood from the patient (using the glucose meter Precision Xceed Pro, Abbott Laboratories, Abbott Park, IL for the former and the automated analyzer UniCell DxC800; Beckman Coulter Inc, Brea, CA for the latter; Table 1). However, we no longer observed this discrepancy after resolution of hypothermia and administration of 2 ampules of 50% dextrose in the Emergency Department.

Questions 1. Did the glucose meter work properly or did it provide erroneous results? 2. If the glucose meter worked properly, what was the underlying cause of the discrepant glucose results between capillary and venous blood? Abbreviations: FDA, United States Food and Drug Administration; QC, quality control 1 Emergency Department, University of Pittsburgh Medical Center Shadyside Hospital, Pittsburgh, PA Departments of 2Emergency Medicine and 3Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA 4 Clinical Laboratories, University of Pittsburgh Medical Center Presbyterian and Shadyside Hospitals, Pittsburgh, PA 5 McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA

*To whom correspondence should be addressed. [email protected]

e156  

Lab Medicine  Fall 2014  |  Volume 45, Number 4

Possible Answers 1. Possible inaccuracy of glucose meter results for critically ill patients has been pointed out previously.1-3 Indeed, the United States Food and Drug Administration (FDA) has emphasized that none of the blood glucose monitoring systems on the market today has regulatory clearance for use in critically ill patients.4,5 In this case, the discrepant readings between the

www.labmedicine.com

Case Study

capillary glucose level via the glucose meter and the venous glucose level via the automated analyzer were diminished within 14 hours, along with the resolution of hypothermia. The performance of the glucose meter used in this case was validated in the daily quality control (QC) procedures. Thus, malfunctioning of the glucose meter is highly unlikely in this case. 2. Raynaud phenomenon involves excessive vasoconstriction with cold temperature, emotional stress, and comorbid conditions, resulting in discoloration of the skin, commonly in the fingers and toes. Pseudohypoglycemia for capillary blood has been reported for patients with Raynaud phenomenon,6-8 presumably because of the prolonged blood transit time in the vasoconstricted capillaries, which increases glucose consumption within the capillary blood.8 This patient had hypothermia-induced Raynaud phenomenon. In this case, although the glucose meter itself was working properly, we obtained inaccurate glucose readings because we used, for analysis, blood from the highly vasoconstricted capillaries (due to Raynaud phenomenon) of the patient. Laboratorians and health care professionals should be aware of the limitations of glucose testing of capillary blood using glucose meters, especially in the critical care setting.

Table 1. Discrepant Glucose Levels in Capillary and Venous Blooda Glucose Level, mg/dL Time After Initial Presentation

Capillary

Venous

0h 6h 14 h

23 56 268

113 321 276

a The capillary glucose level was analyzed via glucose meter (Precision Xceed Pro, Abbott Laboratories, Abbott Park, IL); the venous glucose level was analyzed via automated analyzer (UniCell DxC800; Beckman Coulter Inc, Brea, CA).

Financial or Personal Conflicts of Interest None reported.  LM

References 1. Rebel A, Rice MA, Fahy BG. The accuracy of point-of-care glucose measurements. J Diabetes Sci Technol. 2012;6:396-411. 2. Pitkin AD, Rice MJ. Challenges to glycemic measurement in the perioperative and critically ill patient: a review. J Diabetes Sci Technol. 2009;3:1270-1281. 3. Inoue S, Egi M, Kotani J, Morita K. Accuracy of blood-glucose measurements using glucose meters and arterial blood gas analyzers in critically ill adult patients: systematic review. Crit Care. 2013;17:R48. doi: 10.1186/cc12567. 4. United States Department of Health and Human Services/Food and Drug Administration. Draft guidance for industry and FDA staff: total product life cycle for portable invasive blood glucose monitoring systems. United States Department of Health and Human Services. Food and Drug Administration Web site; 1996.

www.labmedicine.com

5. United States Department of Health and Human Services. Food and Drug Administration. Blood glucose monitoring test systems for prescription point-of-care use: draft guidance for industry and Food and Drug Administration staff. United States Department of Health and Human Services/Food and Drug Administration Web site; 2014.Accessed at: http://www.fda.gov/downloads/MedicalDevices/ DeviceRegulationandGuidance/GuidanceDocuments/UCM380325. pdf. Retrieved October 16, 2014. 6. Atkin SH, Dasmahapatra A, Jaker MA, Chorost MI, Reddy S. Fingerstick glucose determination in shock. Ann Intern Med. 1991;114:1020-1024. 7. Rushakoff RJ, Lewis SB. Case of pseudohypoglycemia. Diabetes Care. 2001;24:2157-2158. 8. El Khoury M, Yousuf F, Martin V, Cohen RM. Pseudohypoglycemia: a cause for unreliable finger-stick glucose measurements. Endocr Pract. 2008;14:337-339.

Fall 2014  |  Volume 45, Number 4  Lab Medicine  e157