Rapid onset asthma: a severe but uncommon manifestation.

BACKGROUND Studies of asthma death and severe life threatening asthma (SLTA) include reports of patients who had rapid onset asthma. A study was undertaken to determine the relative frequency of rapid (< 6 hours duration) and slow (> or = 6 hours) onset attacks in patients admitted to hospital with acute severe asthma, and to establish whether those with rapid onset asthma differ in terms of risk factors for asthma morbidity and mortality such as indices of asthma severity/control, socioeconomic factors, health care, and psychological factors. METHODS A cross sectional study was performed on 316 patients aged 15-49 years admitted with acute severe asthma and interviewed within 24-48 hours of admission. RESULTS Patients underestimated the duration of the index attack. Only 27 (8.5%) were classified as rapid onset. There were more men in the rapid onset group than in the slow onset group (52% versus 26%), and there was evidence of socioeconomic advantage in the patients with rapid onset attacks. The rapid onset group had more previous episodes of SLTA and were more likely to present with SLTA, but there was no difference in length of stay in hospital. The rapid onset group were less likely to have presented to a GP during the index attack and were more likely to have used ambulance services. There was no difference between the groups in any psychological or health care measure. CONCLUSIONS Rapid onset attacks are an important but uncommon manifestation of asthma that are more likely to present with SLTA in patients who are more likely to have had previous SLTA. Male subjects are at increased risk of rapid onset attacks, and socioeconomic disadvantage, deficiencies in health care (ongoing and acute), and psychological factors are no more common in these patients than in those with attacks of slow onset. These data are consistent with the hypothesis that there is a small proportion of patients with rapid onset severe asthma who do not have the usual risk factors associated with asthma morbidity or mortality, and thus require different management strategies.