Serious long-term secondary effects of diabetes mellitus (for example blindness due to retinopathy) can be prevented only by keeping the blood sugar level within narrow limits, corresponding to those of a healthy person, at all times by means of exactly dosed administrations of insulin. For this reason, insulin-dependent diabetics need to measure their blood glucose concentration several times daily and self-administer the required quantity of insulin.
The optimal dosing of insulin administrations, in terms of quantity and frequency, cannot be derived without further ado from measuring values of the blood glucose concentration. In practical application, the selected dosing of insulin is based on the experience made by the attending physician or patient. Typically, a physician prepares for a diabetic a dosing scheme that predetermines not only the quantity and frequency of insulin administrations to meet the basic insulin need but also contains instructions as to how to dose additional insulin administrations in response to elevated measuring values of the blood glucose concentration and meals. In this context, insulin administrations for meeting the basic insulin needs are called basal rate and additional insulin administrations related to meals are called bolus dose.
The general dosing instructions according to which a diabetic determines the dosing of the insulin administrations to be administered taking into consideration measuring values of the blood glucose concentration is called adjustment.
Suboptimal adjustment of the dosing of insulin administrations cannot be detected without further ado even on the basis of a series of measuring values of the blood glucose concentration, since the blood glucose concentration is subject to strong variations throughout the day even in healthy individuals. The article of N. Weintrob et al. titled “Glycemic patterns detected by continuous subcutaneous glucose sensing in children and adolescents with Type 1 Diabetes Mellitus treated by multiple injections vs continuous subcutaneous insulin infusion”, Arch. Pediatr. Adolesc. 158, 677 (2004) follows the approach to assess continuously measured blood glucose concentrations with regard to the adjustment of dosing of insulin administration by means of time integrals of the blood glucose concentration.
In this procedure, an area above a base line that is predetermined by a threshold value of 180 mg/dl and below the blood glucose time curve is determined for a time period Δt of several days. This area is then divided by the time period Δt in order to obtain a parameter that characterizes a hyperglycemic disturbance of glucose metabolism. By the same procedure, a parameter characterizing hypoglycemic disturbances of glucose metabolism is determined by determining an area between a base line that is predetermined by a lower threshold value of 70 mg/dl and the blood glucose time curve for those times at which the blood glucose concentration is less than the respective threshold value.
The known method is called area-under-curve (AUC) calculation. A similar method for diagnosing diabetes is known from WO 2004/043230 A2. Herein, it is recommended to analyze, as a supplement, further features of a measured blood glucose concentration profile, for example the slope.
Methods of this type can be used to generally assess whether or not the insulin dosing of an insulin-dependent diabetic is adjusted well. However, it is essential for a specific recommendation concerning therapy or for optimization of adjustment to detect periods of glycemic instabilities in the glucose profile and their causal relationship to any insulin dosing or intake of food. In particular for persons with varying insulin sensitivity (so-called brittle diabetes), it is basically impossible to attain optimal adjustment of insulin dosing using known methods.