Fingerstick artefactual hypoglycaemia in a patient suffering from Systemic Sclerosis and Raynaud's syndrome

Abstract

Artefactual hypoglycaemia has been defined as a discrepancy between different laboratory measurements and actual blood glucose, regardless of symptoms. Our case illustrates this diagnosis trap. We report the case of a 59 year-old woman, whose glycaemia levels, measured by fingerstick blood glucose, were found to be low (between 34 and 70 mg/dl) on several samples contrasting with normal levels in control venous samples. The fortuitous discovery of low glycaemias was not associated with clinical hypoglycaemia symptoms. The patient had a history of Raynaud's syndrome related to Systemic Sclerosis. The result of cortisol investigations was normal. The ultrasound exam showed a normal pancreas and a fatty liver. The oral hyperglycaemia showed a slight functional hyperinsulinism. The fast test was not in favour of an insulinoma. The artefactual hypoglycaemia reported in this patient with Raynaud's syndrome and systemic sclerosis was due to a low capillary blood glucose level caused by a reduced capillary flow and capillary alterations. As venous access can be difficult in patients with systemic sclerosis, several teams propose the earlobe as an alternative site for the glucose measurements. The lack of clinical symptoms associated with hypoglycaemias measured by fingerstick should be interpreted with caution, depending on the clinical context. In case of doubt, hypoglycaemias should be confirmed by a venous measure, which remains the gold standard. It is important to take into account the patient's history, which can be a cause of artefactual hypoglycaemia.