The present study was designed to determine the IgE cut-off values for allergic and non-allergic asthma by the receiver operating characteristic analysis.

A prospective study was conducted on 149 asthma patients (99 allergic, 50 non-allergic) and 50 controls in GATA Haydarpaşa Hospital, Department of Allergy, between January 2005 and December 2006. Participants were evaluated for atopic allergic disease (asthma) and then skin was tested using the prick test method. The receiver operating characteristic (ROC) analysis was carried out to determine and calculate the cut-off points for patients with allergic and non-allergic asthma. The cut-off point was determined by means of likelihood ratio statistic.

The median total IgE levels of allergic (207 (20-962) U/ml) and non-allergic (40 (6.80-882) U/ml) asthma patients were significantly higher than the controls (26 (2-220) U/ml) (p<0.001). The cut-off point of total IgE for discriminating allergic and non-allergic from controls was 220 (sensitivity: 48.0%; specificity: 98.0%) and 176 (sensitivity: 20.0%; specificity: 96.0%) in patients with asthma, respectively. The total IgE cut-off value for allergic asthmatic vs. non-asthmatic patients was 442 (sensitivity: 17.0%; specificity: 96.0%) based on likelihood ratio statistic. The sensitivity values of total IgE were low, while the specificity values were considerably high.

In summary, the obtained results points out that total IgE level cut-off points may be helpful for discriminating allergic from non-allergic patients with asthma.