Methods:The clinical records of 1,136 adult patients with suspected asthma, for whom test data for serum IgA level and methacholine-AHR were available, were reviewed retrospectively. The AHR/allergy indices were compared among patient groups with low (<140 mg/dL, Group I), intermediate (140-280 mg/dL, Group II), or high (≥280 mg/dL, Group III) IgA levels in serum.
Results: The rate of skin sensitization to HDM progressively decreased from 30.0% in Group I (n=139) to 26.8% and 18.5% in Groups II (n=684) and III (n=313), respectively (P=0.003). Although both the HDM sensitization degree and the IgA level were significantly related to age, the adjusted odds ratio (OR) of association of a high IgA level (≥280 mg/dL) with HDM sensitization was significant (0.617, 95% CI: 0.415-0.916, P=0.017). Among younger subjects (≤45 years of age) with AHR (n=234), the prevalence of moderate/severe AHR progressively decreased from 70.6% in Group I (n=34) to 52.3% and 47.1% in Groups II (n=149) and III (n=51), respectively (P=0.045). A low IgA level (<140 mg/dL) was a significant risk factor for moderate/severe AHR (OR 2.306, 95% CI 1.049-5.071, P=0.038).
Conclusion: Sensitization to HDM and methacholine-AHR were significantly associated with low serum IgA levels in suspected asthmatics, even when those levels were normal.