Accuracy of an Electrochemical Sensor for Measuring Capillary Blood Ketones by Fingerstick Samples During Metabolic Deterioration After Continuous Subcutaneous Insulin Infusion Interruption in Type 1 Diabetic Patients

Abstract

OBJECTIVE—This study was designed to test the accuracy of capillary ketonemia for diagnosis of ketosis after interruption of insulin infusion. RESEARCH DESIGN AND METHODS—A total of 18 patients with type 1 diabetes treated by external pump were studied during pump stop for 5 h. Plasma and capillary ketonemia and ketonuria were determined every hour from 7:00 a.m. (time 0 min = T0) to 12:00 p.m. (time 300 min = T300). Plasma β-hydroxybutyrate (β-OHB) levels were measured by an enzymatic end point spectrophotometric method, and capillary β-OHB levels were measured by an electrochemical method (MediSense Optium meter). Ketonuria was measured by a semiquantitative test (Ketodiastix). Positive ketosis was defined by a value of ≥0.5 mmol/l for ketonemia and ≥4 mmol/l (moderate) for ketonuria. RESULTS—After stopping the pump, concentrations of β-OHB in both plasma and capillary blood increased significantly at time 60 min (T60) compared with T0 (P < 0.001), reaching maximum levels at T300 (1.30 ± 0.49 and 1.23 ± 0.78 mmol/l, respectively). Plasma and capillary β-OHB values were highly correlated (r = 0.94, P < 0.0001). For diagnosis of ketosis, capillary ketonemia has a higher sensitivity and negative predictive value (80.4 and 82.5%, respectively) than ketonuria (63 and 71.8%, respectively). For plasma glucose levels ≥250 mg/dl, plasma and capillary ketonemia were found to be more frequently positive (85 and 78%, respectively) than ketonuria (59%) (P = 0.017). The time delay to diagnosis of ketosis was significantly higher for ketonuria than for plasma ketonemia (212 ± 67 vs. 140 ± 54 min, P = 0.0023), whereas no difference was noted between plasma and capillary ketonemia. CONCLUSIONS—The frequency of screening for ketosis and the efficiency of detection of ketosis definitely may be improved by the use of capillary blood ketone determination in clinical practice.