[Influence of age on blood glucose levels: percentile reference intervals determined on ambulatory patients]

Data of routine chemical and hematological laboratory tests regarding outpatients were collected in four different hospitals of the provinces of Ferrara, Rovigo and Bologna. Data of about 1500 subjects per hospital were cumulated without preliminary selection of patients; sex, age and pregnancy status were also recorded. At the end of the collection, the second (and third) record of the same patient was discarded; only those referring to the first examination were retained. In this report we consider only the values of the blood sugar level which were obtained by enzymatic methods. Descriptive statistics and regression analysis were performed utilizing a CDC CYBER 70/76 computer. The means and the variances of the data collected at the four hospital laboratories were very similar (Tab 1). The interlaboratory analysis of variance was poorly significant. All frequency distributions were leptocurtic and skewed to the right (Fig. 1). The blood sugar level tend to increase with age (Tab. 2). This correlation is graphically depicted in a two-dimensional plot (Fig 2) in which the regression line and the 2, 5 and 97,5 percentile levels corrected for age were also reported. We think that this diagram may be more helpful to the clinicians interpreting laboratory results than the usual "normal values".