The predictive value of IgE as biomarker in asthma.

BACKGROUND

The evidence for a causal relationship between allergens and asthma depends on epidemiologic findings showing a strong association between specific immunoglobulin E (IgE) antibodies or total IgE and asthma.

OBJECTIVE

To clarify the relationship between total serum IgE levels and asthma.

STUDY DESIGN

A cross-sectional study.

PATIENTS AND METHODS

A total of 562 asthmatic patients were included in the study, and their age range was from 17 to 52 years. The subjects included in the study were outpatients from the Asthma and Allergy Centre or Samara General Hospital outpatients Clinic. The diagnosis of asthma was performed by a specialist physician and was established according to the National Heart Blood and Lung Institute/World Health Organization (NHLBI/WHO) workshop on the Global Strategy for Asthma.

RESULTS

This study indicated that mean serum IgE level was 554 +/- 447 IU/mL in asthmatic patients, while that of the control population was 69 +/- 33 IU/mL. There was no overlap in the values of 95% confidence interval (CI) of higher control limit and lower asthmatic limit values. Addition of two standard deviations to the mean IgE value of the control group (134 IU/mL) does not overlap with the lower 95% CI of the asthmatic group. However, serum IgE was within normal values in 5.9% of asthmatic patients in our study population. There was an inverse correlation between serum IgE levels and forced expiratory volume in 1 second (FEV(1)) predicted percent for patients with asthma (r = -0.73, p < 0.0001). The predictive value of serum IgE in asthma was determined using Receiver Operating Characteristics (ROC) curve method. From the ROC curve, it can be seen that it is possible to get both high sensitivity and high specificity if the right cut-off value was chosen. In fact, a cut-off of 200 IU/mL would indicate sensitivity of 93% and specificity of 91% in this group of patients and control subjects. Following immunotherapy there was 36% reduction in total serum IgE level. The value of IgE was significantly reduced (p < 0.001) from 956 +/- 378 IU/mL at baseline to 613 +/- 194 IU/mL after treatment.

CONCLUSION

Serum IgE level was predictive in asthma, and it may be used to differentiate between asthmatic and non-asthmatic individuals in conjunction with other biomarkers. Specific immunotherapy reduced serum total IgE level in 36% of patients with asthma.