Bronchial Reactivity 8-15 Years after Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Infection (LRI)

Abstract 1007 Poster Session IV, Tuesday, 5/4 (poster 88)

Objective: To determine the present levels of respiratory function (and airway reactivity) of subjects hospitalized with RSV LRI in the Washington Metropolitan area between 1983-1990.

Persons and Methods: Subjects < 1 year of age admitted with RSV LRI were identified by chart review, age at time of diagnosis, and duration of symptoms prior to hospitalization. Patients with ongoing need for intubation and mechanical ventilation were excluded. In addition to a questionnaire detailing the use of asthma meds, ER visits, home conditions, parents with history of asthma, use of asthma meds, crowding index, smoking, pets, CHD, BPD, apnea, ICU admissions; participants had pulmonary function tests (PFT) including methacholine challenge (MC). PFT's included FVC₁, FEV₁, FEV₁/FVC, FEF_25-75% compared to standard for age, height, and gender. Interpretation: FEV₁/FVC > 80% and FVC > 80 % of predicted, normal/mild; FEV₁/FVC > 60% and FVC < 80% predicted, moderate; FEV₁/FVC < 60%, severe. MC nl if < 20% drop in FEV₁ at all concentrations; mild reactivity if < 20% FEV drop at 25 mg/ml, moderate drop at 1.25-10 mg/ml (4-dose steps) and severe reactivity drop at < 0.6 mg/ml (4-dose steps). If the baseline FEV₁ < 70% predicted, no MC test was conducted. Patients with FEV₁ < 70% of predicted were given bronchodilator aerosol and classified as severely reactive if response ≤15%. All data was evaluated blindly by pulmonologists. Statistics were obtained by McNemar Test. Results: Thus far, 54 patients ages 8-15 years (mean age 11 years), male/female ratio 1:1 have completed PFT, 4 (7%) had moderate to severe changes in baseline pulmonary function. However, 30 (56% versus greater than 12.5% expected population reactivity) had shown increased reactivity on MC (Exact p value 2×10^-4 versus post MC). Patients with a family history of asthma also showed a similar pattern of MC bronchial reactivity 19/29 (66%) compared to abnormal baseline PFT 3/26, 12% (Exact p value 9×10^-2). Those without family history showed similar trends 1/24 (4%) with abnormal PFT at baseline versus 12/25 (48%) on challenge (Exact p value 1.8×10^-3). Conclusions: RSV may predispose to bronchial reactivity including those without a family history of asthma. This reactivity is not readily apparent without a provocative challenge.

Supported in part by a grant from ICN Pharmaceuticals, Costa Mesa, California.