Case-control study of severe life threatening asthma (SLTA) in adults: demographics, health care, and management of the acute attack

Background-Severe life threatening asthma (SLTA) is important in its own ri ght and as a proxy for asthma death. In order to target hospital based inte rvention strategies to those most likely to benefit, risk factors for SLTA among those admitted to hospital need to be identified. A case-control stud y was undertaken to determine whether, in comparison with patients admitted to hospital with acute asthma, those with SLTA have different sociodemogra phic and clinical characteristics, evidence of inadequate ongoing medical c are, barriers to health care, or deficiencies in management of the acute at tack. Methods-Seventy seven patients with SLTA were admitted to an intensive care unit (pH 7.17 (0.15), Paco(2) 10.7 (5.0) kPa) and 239 matched controls (by date of index attack) with acute asthma were admitted to general medical w ards. A questionnaire was administered 24-48 hours after admission. Results-The risk of SLTA in comparison with other patients admitted with ac ute asthma increased with age (odds ratio (OR) 1.04/year, 95% CI 1.01 to 1. 07) and was less for women (OR 0.36, 95% CI 0.20 to 0.68). These variables were controlled for in all subsequent analyses. There were no differences i n other sociodemographic features. Cases were more likely to have experienc ed a previous SLTA (OR 2.04, 95% CI 1.20 to 3.45) and to have had a hospita l admission in the last year (OR 1.86, 95% CI 1.09 to 3.18). There were no differences between cases and controls in terms of indicators of quality of ongoing asthma specific medical care, nor was there evidence of disproport ionate barriers to health care. During the index attack cases had more seve re asthma at the time of presentation, were less likely to have presented t o general practitioners, and were more likely to have called an ambulance o r presented to an emergency department. In terms of pharmacological managem ent, those with SLTA were more likely to have been using oral theophylline (OR 2.14, 95% CI 1.35 to 3.68) and less likely to have been using inhaled c orticosteroids in the two weeks before the index attack (OR 0.69, 95% CI 0. 47 to 0.99). While there was no difference in selfmanagement knowledge or b ehaviour scores, those with SLTA were more likely to have inappropriately u sed oral corticosteroids during the acute attack (OR 2.09, 95% CI 1.02 to 4 .47). Conclusions-In comparison with those admitted to hospital with acute severe asthma, patients with SLTA were indistinguishable on sociodemographic crit eria (apart from male predominance), were more likely to have had a previou s SLTA or hospital admission in the previous year, had similar quality ongo ing asthma care, had no evidence of increased physical, economic or other b arriers to health care, but had demonstrable deficiencies in the management of the acute index attack. Educational interventions, while not losing sig ht of the need for good quality ongoing care, should focus on providing ind ividual patients with better advice on self-management of acute exacerbatio ns.