The Po River Delta epidemiological survey: Reference values of total serumIgE levels in a normal population sample of North Italy (8-78 yrs)

The aim of this paper was to define, for the first time in Italy, normal le vels of total serum IgE in a general population sample of North Italy. Tota l serum IgE in 1905 subjects, living in Po Delta area (near Venice), were m easured by PRIST method. Normal values were derived from 558 subjects witho ut asthma and/or asthmatic/rhinitic symptoms, noncurrent smokers, skin pric k-test negatives ('normals'). Cut-off values to differentiate 'normals' fro m the remaining part of the sample ('others'), from asthmatic, and from rhi nitic subjects, were established with the IgE value midway between the uppe r limit of the 95% confidence intervals (CI) of the geometric mean for 'nor mals' and the lower limit for 'others', asthmatics, and rhinitics, respecti vely. Geometric mean of normal children-adolescents was 45 kU/L (SD: 2.6; 9 5% CI: 38-63). In normal adults geometric mean was 29 kU/L (SD: 3.3; 95% CI : 25-40) in males and 19 kU/L (SD: 3.8; 95% CI: 16-22) in females. The diag nostic sensitivity of IgE test was low, while the specificity was very high . A good positive predictive value in discriminating 'normals' from 'others ' was found, on the contrary, we found a good negative predictive value in discriminating 'normals' from asthmatics or from rhinitics. In conclusion, our results confirm that it is necessary to provide separate total serum Ig E reference values for what concerns age in children-adolescents and in adu lts, and gender, in adults. Low serum IgE are helpful to exclude allergic a sthma or rhinitis level of total.