Background A small proportion of patients with long standing severe asthma develop irreversible airway obstruction (persistent airflow limitation (PAL)). There is no agreed definition of PAL in children, but pragmatically, most would define it as post steroid, post-bronchodilator FEV₁ percent predicted <80% or Z score less than −1.96, with normative data from appropriate reference populations despite optimal therapy. However, there is no agreement on the dose, duration or route of administration of steroids to determine the optimal spirometry that a child can achieve.

Hypothesis A single intramuscular dose of triamcinolone and acute bronchodilator are insufficient to determine optimal lung function and reliably diagnose PAL. The aim of this study was to determine whether forced expired volume in 1 second (FEV₁) 2–4 weeks after a single dose of triamcinolone and acute bronchodilator administration reflect the best obtained in the following year in patients with severe, therapy resistant asthma.

Patients and Methods 39 children age 5–16 received triamcinolone; the FEV₁ was measured before the treatment, after triamcinolone and during the 12-month period. The highest follow-up FEV₁ was compared with post-steroid post-post-bronchodilator FEV₁.

Results In the year following the 1st dose of triamcinolone 25 (64%) of 39 patients exceeded their immediate post-steroid trial target lung function by >9% predicted. 13 out of 39 patients (33.3%) achieved FEV₁ of >80% predicted at the 1st follow-up. If the diagnosis of PAL had been made just on the steroid trial, 16 patients would have been wrongly given this label; only 10 children were ultimately diagnosed with PAL. 13 of 39 patients received multiple (2–4) doses in 4 weeks intervals and only in 9 of them only the data was analysable. In this small group, the median and interquartile range of FEV₁ were significantly higher (75 vs 68 and 38.75 vs 17) following the 3^rd dose of triamcinolone than after the 1^st.

Conclusion Reliance on a single dose of triamcinolone plus acute administration of ß-2 agonist will lead to an overdiagnosis of PAL in children with severe asthma.