Capillary blood tests measure whole blood glucose as opposed to venous samples which measure plasma glucose. It is used for the care of people with diabetes, as a monitoring tool, giving a guide to blood glucose levels, at a specific moment in time. Capillary blood glucose monitoring was first established in the 1970s using glucometers. With time, the use of glucometers has become easier and faster, with much smaller blood samples, yielding results in a matter of seconds. Today they are used routinely in health care, for the easier achievement of glycaemic targets and diabetic emergencies. Without such technology, intensive glucose control including insulin pump therapy would not have become a reality. Glucometers have also relieved a great amount of anxiety over the management of hypoglycaemia. Today however, we rely so much on capillary blood glucose measurements forgetting its limitations. This article will discuss the pitfalls and limitations of capillary blood glucose monitoring (1, 2). Accuracy goals for home glucose monitorsThe goals for glucometer accuracy have been quite variable. Clarke et al. proposed an accuracy grid to establish a more expansive set of goals for glucometer usage taking into account clinical accuracy, defined as within 20% of the laboratory glucose (3). For glucose levels above 75 mg/dl, the International Organization for Standardization (ISO) recommends a goal for glucometer error of within 20% when compared with a reference glucose sample, but for glucose levels less than 75 mg/dl, the goal is for 95% of readings to be within 15 mg/dl of the reference. The U.S. Food and Drug Administration goal for glucometers is within 20% of the reference value, when glucose is greater than 100 mg/dl and within 20 mg/dl when glucose is less than 100 mg/dl (4, 5).Although there is no universally binding standard, guidelines issued by ISO are widely acknowledged. Assuming a meter meets the ISO guideline, then a true glucose level of 55 mg/dl could in fact yield a reading of as low as 40 or as high as 70 mg/dl. It could be particularly hazardous in a patient with hypoglycaemia unawareness who would consider the reading of 70 mg/dl as reassuring for a true value of 55 mg/dl, which needs prompt corrective action. At the other end of the spectrum, a true value of 350 mg/dl might register as low as 280 or as high as 420 mg/dl. This could have some consequences, especially in intensive care situations, where insulin infusion algorithms aim at achieving tight glycaemic control (4).

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A right homogeneous adrenal tumor was found incidentally, during abdominal computed tomography in a 72-year-old female patient, presenting with hypertension of 2 years duration. She had an elevated Aldosterone: Renin Ratio (ARR) and primary hyperaldosteronism was confirmed with a fludrocortisone suppression test. Plasma basal cortisol and adrenocorticotropic hormone (ACTH) levels were normal, but the plasma cortisol concentration could not be suppressed with dexamethasone. Therefore, an adrenal cortical adenoma with primary hyperaldosteronism and subclinical hypercortisolism was suspected. Urinary total metanephrines and vanillylmandelic acid (VMA) levels were also marginally elevated, indicating the possibility of a pheochromocytoma. After right adrenalectomy, the tumour was histologically demonstrated to be a pheochromocytoma, and the levels of all three hormone groups viz corticosteroid, mineralocorticoid and metanephrine levels normalized, indicating the possibility of a cosecretory small adrenocortical microadenoma.

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Suren to some of us and Rama to others was certainly one of the outstanding physicians of our time. Born to a well known Tamil hindu family, he had his early education at CMS Ladies College Colombo and then Royal College Colombo.