Asthma: acute exacerbation: relapse could be predicted.

Clinical bottom line (level 1b)

  1. Nearly half of adult patients who visited hospital with an exacerbation of asthma had a relapse within eight weeks.
  2. Patients with acute severe asthma were more likely to suffer a relapse in the next 8 weeks, if they had any of the following:
    • 3 or more ED visits within the last 6 months (NNF = 5 for 8 weeks)
    • difficulty performing work or other activities due to physical health within last 4 weeks (NNF = 6 for 8 weeks)
    • left hospital within 24 hours without achieving 50% predicted PEFR (NNF = 6 for 8 weeks)
  3. The more risk factors patients had, the greater their risk of relapsing.
McCarren et al: Journal of Clinical Epidemiology 1998; 51 (2): 107-118
Expires November 2002

The study

Inception cohort study with objective outcomes, adjusted for confounding factors, not validated in an independent set of patients.

Setting: university hospital, USA

284 patients (aged mean 35 years, 60% male) acute severe asthma (presenting PEFR 27% predicted)

Excluded if
  • discharged from emergency department within three hours
  • imminent danger of respiratory failure
  • <18 or >55 years old
  • pO 2 = 55 mmHg, pCO 2 = 45 mmHg
  • PEFR = 80 l/mmHg after first beta-agonist treatment
  • factors suggesting COPD (asthma onset after 45 and = 20 pack-year history of smoking)
  • emergency department documented best PEFR less than their discharge criteria (usually 50% predicted)
  • pregnancy
  • diagnosis of pneumonia, congestive heart failure or restrictive lung disease



    • Factors studied:
  • relapse
  • 3 or more visits to ED within last 6 months
  • difficulty performing work or other activities due to physical health within last 4 weeks
  • left before 24 hours without achieving 50% predicted PEFR


    • All patients had nebulised beta-agonists and steroids in hospital, and were discharged home on theophyllines, beta-agonists and steroid metered-dose inhalers, and 9 to 11 days of oral steroids.

    Multivariate regression analysis was used to adjust for confounding factors.

    86% followed for 8 weeks
    Outcomes studied:
  • relapse

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    relapse 8 weeks 128/284 45%
    (39% to 51%)

    prognostic factor for
    relapse     		time to outcome control rate (%) adjusted OR
    (95% CI)    		 NNF+
    (95% CI)
    3 or more visits to ED within last 6 months 8 weeks /
    (41%)     		2.3
    (1.6 to 3.4)     		5
    (3 to 9)
    difficulty performing work or other activities due to physical health within last 4 weeks 8 weeks /
    (70%)     		2.7
    (1.6 to 4.3)     		6
    (5 to 11)
    left before 24 hours without achieving 50% predicted PEFR 8 weeks /
    (16%)     		2.6
    (1.6 to 4.1)     		6
    (4 to 14)

    • Risk factors and relapse rates:
      • 3 risk factors: prevalence 4.6%: relapse 100% (95% CI: 79% to 100%)
      • 2 risk factors: prevalence 32%: relapse 63% (95% CI: 53% to 73%)
      • 1 risk factor: prevalence 49%: relapse 32% (95% CI: 24% to 39%)
      • 0 risk factors: prevalence 14%: relapse 14% (95% CI: 3.8% to 26%)

    Comments

    1. Patients were urban, poor and mainly African-American.
    2. Clinical prediction rule created, which needs to be validated in an independent set of patients.
    3. Merely identifying a group is pointless - this needs to spur clinicians on to further action in decreasing the number of relapses in the highest risk group.

    Citation

    1. McCarren M, McDermott MF, Zalenski RJ, et al: Prediction of relapse within eight weeks after an acute asthma exacerbation in adults. Journal of Clinical Epidemiology 1998; 51 (2): 107-118
    Search Terms: acute asthma in Cochrane
    Contributor: Chris Ball and Clare Wotton, June 2000
    Reviewer: Jean-Blaise Wasserfallen

    Clinical Question.
    Patient acute severe asthma
    Intervention or Exposure risk factors
    Outcome relapse