ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 64 035 | DOI: 10.1530/endoabs.64.035

CREST syndrome diagnosed because of faulty point-of-care glycaemia: a case report

Mertens Jonathan1, Haddad Maryam1 & de Block Christophe2

1Department of Geriatrics, ZNA Campus Stuivenberg, Antwerp, Belgium; 2Department of Endocrinology, UZA, Edegem, Belgium.

Background: Glycaemia point-of-care testing (POCT) is performed with fingerstick capillary whole-blood glucose measurement. These values normally 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 defined as a discrepancy between POCT and plasma glucose measurements1. This can occur in cases of decreased capillary flow which leads to deceleration of glucose transit through tissues and consequently increased extraction by the tissues1,2

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. However, the patient expressed no clinical signs of hypoglycemia. Plasma glucose measurement was 91 mg/dl. She had no history of diabetes mellitus, nor of malignancy or auto-immune disease. 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. Raynaud Phenomenon and sclerodactyly is associated with artifactual hypoglycemia1,3,4,5. Further work-up for systemic disease revealed she had complaints of dysphagia. She featured facial telangiectasia. She had positive ANF-antibodies and anti-centromere antibodies. The patient was therefore clinically 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 increased3,5.

Conclusions: POCT is useful to check glucose values. However, artifactual hypoglycemia can occur in settings of 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 are rare but can falsify capillary glucose. Serum glucose must be compared with POCT to objectify true hypoglycemia.

References: 1. Valentina D. Tarasova, Mohsen Zena, Marc Rendell. Artifactual Hypoglycemia: An Old Term for a New Classification. Diabetes Care May 2014, 37(5) e85–e86; DOI: 10.2337/dc13-2891.

2. McGuire EA, Helderman JH, Tobin JD, Andres R, Berman M. Effects of arterial versus venous sampling on analysis of glucose kinetics in man. J Appl Physiol 1976;41:565–573.

3. Bishay RH, Suryawanshi A. Artifactual Hypoglycaemia in Systemic Sclerosis and Raynaud’s Phenomenon: A Clinical Case Report and Short Review. Case Rep Endocrinol. 2016;2016:7390927. doi:10.1155/2016/7390927.

4. El Khoury, Marc & Yousuf, Farheen & Martin, Vincent & Cohen, Robert (2008). Pseudohypoglycemia: A cause for Unreliable Finger-Stick Glucose Measurements. Endocrine Practice: Official Journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists. 14. 337–9.

5. Fleischmajer R, Perlish JS. Capillary alterations in scleroderma. Journal of the American Academy of Dermatology, 1980;2(2):161–170.

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