Introduction Patients with asthma are prone to recurrent infective exacerbations, due to viral or bacterial infections. We have previously presented retrospective data, demonstrating significantly reduced lung function in severe asthma patients with specific antibody deficiency. The prevalence and impact of specific antibody deficiency in this patient group is not known.
Aim We aimed to determine the prevalence of specific antibody deficiency and its association with markers of disease severity.
Methods We prospectively collected data from all new patients attending the regional severe asthma clinic. We recorded demographic details and markers of disease severity including: BTS treatment step, inhaled corticosteroid (ICS) dose, spirometry, blood and sputum eosinophil count, radiological findings such as bronchiectasis and bronchial wall thickening, exacerbations in the last year and ITU admissions. Specific antibody levels to Haemophilus Influenzae (Streptococcus Pneumoniae (<0.35 μg/ml to at least 6 of the 12 serotypes classed as deficient) were measured.
Results Data for 53 patients (39F), mean (SD) age 49.6 (15.9) years were available. Mean (SD) FEV1 was 69 (22)% predicted, ICS dose 1914 (1337) micrograms, and BMI 31.5 (8.6) kg/m2. All were at BTS step 3–5. Information on specific antibody levels was available for 43 and 45 patients for H Influenzae and S pneumoniae respectively and for both in 42 patients. Overall out of the 42 patients 35 (83%) were deficient to one or both the organisms. Of these 13 (31%) were deficient to H Influenzae alone, 5(12%) to S pneumoniae alone, and 17 (40.5%) to both. Looking at each organism separately 30 (70%) out of 43 were deficient to H Influenzae and 23 out of 45 (51%) were deficient to S pneumoniae. Of the 32 patients for whom data were available 20 (63%) had 7 or more exacerbations in the preceding year and two thirds of these had bronchial wall thickening on their CT scans. A third of patients (30%) reported at least one ITU admission. The presence of specific antibody deficiency did not correlate with any clinical or radiological findings.
Conclusion Specific antibody deficiency to H influenza and S pneumoniae is remarkably common in moderate to severe asthma. Further studies are required to determine the clinical significance of this finding.