Limited preanalytical requirements for insulin measurement

OBJECTIVES: To evaluate the stability of insulin in serum and plasma under conditions relevant for the transport of samples from outpatient clinics to a centralized laboratory. DESIGN AND METHODS: Venous blood samples were taken from 15 volunteers and processed either immediately or after storage at room temperature for 24 h. The effect of EDTA or sodium fluoride on insulin results was investigated. RESULTS: Insulin was found to be stable in EDTA-containing tubes at room temperature for at least 24 h, whereas significantly lower concentrations were found if samples without additives or potassium fluoride as an additive were used. CONCLUSIONS: If shipment of patients' samples for insulin measurement from an outpatient clinic to a centralized laboratory can be performed within 24 h, centrifugation and freezing of plasma is not required. These findings facilitate a widespread application of insulin measurements to characterize and follow-up individual insulin sensitivity.