Asthma: acute exacerbation: relapse was more likely in frequent attenders.

Clinical bottom line (level 1b)

  1. Relapses were common in the next 10 days in children discharged home following an episode of acute asthma.
  2. Patients with frequent visits to the emergency department were at increased risk of relapse (NNF = 4 for unknown) (for four or more previous visits).
  3. Patients who received short-acting theophyllines in the emergency department were at reduced risk of relapse (NNF = 5 for 10 unknown) .
  4. A clinical prediction rule did not usefully help identify patients at risk.
Ducharme and Kramer: Journal of Clinical Epidemiology 1993; 46 (12): 1395-1402
Expires November 2002

The study

Inception cohort study with objective outcomes, adjusted for confounding factors, validated in an independent set of patients.

Setting: emergency department, university hospital, Canada

314 patients (aged range 1 to 18 years, 65% male) children ) with acute asthma subsequently discharged from emergency department (defined as signs and symptoms of respiratory obstruction with clinical improvement with nebulised beta-agonists)

Excluded if
  • cystic fibrosis, bronchopulmonary dysplasia, cardiac disease or suspicion of foreign body aspiration
  • initial visit a relapse
  • more than two attendances within ten days



    • Factors studied:
  • 10 or more ED visits in past year (versus zero visits)
  • 7-9 visits
  • 4-6 visits
  • 1-3 visits
  • short-acting theophylline in the emergency department in adequate dosage (versus none)
  • short-acting theophylline in the emergency department in suboptimal dosage


    • All patients received albuterol 0.1 mg/kg to a maximum of 5 mg hourly or more with or without steroids, and other bronchodilators.

    Logistic regression analysis was performed on risk factors.

    ?100% followed for 10 days
    Outcomes studied:
  • relapse repeat emergency department visit for asthma

      • derivation set: 211 patients (aged mean 7.3; 62% male)
      • validation set: 103 patients (aged mean 7.6; 68% male)

    The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    relapse 10 days 96/314 31%
    (26% to 36%)

    prognostic factor for
    relapse     		time to outcome control rate (%) adjusted OR
    (95% CI)    		 NNF+
    (95% CI)
    10 or more ED visits in past year ? 33/211
    (16%)     		4.1
    (1.4 to 11.5)     		4
    (2 to 25)
    7-9 visits ? 2.9
    (1.3 to 6.2)     		5
    (3 to 26)
    4-6 visits ? 2.0
    (1.2 to 3.4)     		9
    (4 to 38)
    1-3 visits ? 1.4
    (1.1 to 1.8)     		20
    (10 to 76)
    short-acting theophylline in the emergency department in adequate dosage ? 116/211
    (55%)     		0.4
    (0.2 to 0.8)     		-5
    (-3 to -18)
    short-acting theophylline in the emergency department in suboptimal dosage ? 0.6
    (0.5 to 0.9)     		-8
    (-6 to -38)

    • clinical prediction rule: positive if: four or more visits to emergency department and no use of theophylline in department
    • derivation set:
      • sensitivity 73%; specificity 53%
      • LR+ 1.6; LR- 0.51
    • validation set:
      • specificity 73%; specificity 50%
      • LR+ 1.5; LR- 0.54
    • There was not enough data available to calculate the confidence intervals.

    Comments

    1. Significant changes have occurred in asthma management since this study - for example few patients were sent home on steroids unlike more current practice. This may explain the relatively high relapse rate.
    2. It has become unusual to prescribe short-acting theophylline in emergency care setting, and their effect may be very different when steroids have been given.

    Citation

    1. Ducharme FM, and Kramer MS: Relapse following emergency treatment for acute asthma: can it be predicted or prevented?. Journal of Clinical Epidemiology 1993; 46 (12): 1395-1402
    Search Terms: reference from acute asthma chapter in Lee, Hsu, Stasior: Quick Consult Manual to Evidence-based medicine: publ. Lippincott-Raven 1997
    Contributor: Chris Ball and Clare Wotton, November 2000
    Reviewer: Mitsuhiro Kamei

    Clinical Question.
    Patient children with acute asthma
    Intervention or Exposure risk factors
    Outcome relapses