Detection of nocturnal hypoglycemia in insulin-treated diabetics by a skin temperature--skin conductance meter.

The efficacy and credibility of a skin temperature--skin conductance meter (Teledyne Sleep Sentry) for detecting hypoglycemia was studied during night-time in 22 adult insulin-treated diabetics. Capillary blood glucose concentration was measured 99 times (when the alarm sounded, in case of hypoglycemic symptoms, and at 3 a.m.). Hypoglycemia was defined as a capillary blood glucose concentration of less than or equal to 3 mmol/l. Blood glucose was measured 61 times in connection with sounding of the alarm and 38 times without the alarm sounding. At 3 a.m. the Sleep Sentry sounded the alarm 22 times, of which hypoglycemia was present 6 times giving a diagnostical specificity or diagnostical true positive rate of 0.27 (95% confidence limits 0.11-0.50). In 35 of 38 cases of no alarm the blood glucose was greater than 3 mmol/l, giving a diagnostical sensitivity of 0.92 (95% confidence limits 0.79-0.98). The Sleep Sentry sounded the alarm in 6 of 9 cases of hypoglycemia, giving a nosological sensitivity of 0.67 (95% confidence limits 0.30-0.93). The Sleep Sentry did not sound the alarm in 35 of 51 cases of non-hypoglycemia, giving a nosological specificity of 0.69 (95% confidence limits 0.54-0.81). In other words, the Sleep Sentry detects about 2/3 of blood glucose values less than or equal to 3 mmol/l, but in addition it sounds a false alarm in 2/3 of the cases.