Endocrine Abstracts

Background: Glycemia point-of-care testing (POCT) is performed with fingerstick capillary whole-blood glucose measurement. These values correlate well with plasma glucose values. Hypoglycemia can be observed with POCT but should always be confirmed on plasma. True hypoglycemia must meet Whipple’s triad: signs/symptoms of hypoglycemia; low plasma glucose; improvement after glucose administration. Artifactual hypoglycemia is a discrepancy between POCT and plasma glucose and occurs in cases of decreased capillary flow.

Case Presentation: A 86-year-old woman was admitted because she fell in her nursing home. Primary assessment POCT measured a glucose of 20 mg/dl. There were no signs of hypoglycemia. Plasma glucose was 91 mg/dl. She had no history of diabetes mellitus. HbA1c measured 42 mmol/mol. C-peptide was never elevated. POCT was compared multiple times with plasma glucose and showed regular discrepancy. POCT using blood from the ear lobe however correlated strongly with plasma glucose. Clinical examination revealed sclerodactyly and Raynaud’s phenomenon. She had complaints of dysphagia and had facial telangiectasia. She had positive ANF-antibodies and anti-centromere antibodies. The patient was therefore diagnosed with CREST syndrome, the limited cutaneous variant of systemic sclerosis. Due to the sclerodactyly, capillary blood flow is decreased, therefore the rate of tissue glucose withdrawal is increased.

Conclusions: POCT is useful to check glucose values. However, artifactual hypoglycemia can occur in decreased capillary flow or increased glycolysis. Patients presenting with measured hypoglycemia but without symptoms of hypoglycemia do not fulfill Whipple’s triad and should raise suspicion for other etiologies. Connective tissue diseases such as systemic sclerosis can falsify capillary glucose.