Predicting future risk of asthma exacerbations using individual conditional probabilities

J Allergy Clin Immunol. 2011 Jun;127(6):1494-502.e3. doi: 10.1016/j.jaci.2011.01.018. Epub 2011 Feb 18.


Background: Determination of future risk of exacerbations is a key issue in the management of asthma. We previously developed a method to calculate conditional probabilities (π) of future decreases in lung function by using the daily fluctuations in peak expiratory flow (PEF).

Objective: We aimed to extend calculation of π values to individual patients, validated by using electronically recorded data from 2 past clinical trials.

Methods: Twice-daily PEF data were analyzed from 78 patients with severe (study A) and 61 patients with poorly controlled (study B) asthma. For each patient, the π value was calculated from 5000 PEF data points simulated based on the correlation and distribution properties of observed PEF. Given an initial PEF, the π value was defined as the probability of a decrease in PEF to less than 80% of predicted value on 2 consecutive days within a month. These probabilities were then compared with actual occurrences of such events and clinically defined exacerbations within the following month.

Results: π Values were related to actual occurrences of decreases in PEF (adjusted R(2) > 0.800 for both studies). Every increase of 10% in π value was associated with an odds ratio of having a future exacerbation of 1.24 (95% CI, 1.07-1.43) for study A and 1.13 (95% CI, 1.02-1.26) for study B, with better sensitivity and specificity than clinic-measured FEV(1).

Conclusion: These results from 2 independent datasets with differing asthmatic populations and differing exacerbation criteria provide support that clinically relevant quantification of individual future risk of exacerbations is possible.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Asthma / etiology*
  • Asthma / physiopathology*
  • Asthma / therapy
  • Disease Progression
  • Effect Modifier, Epidemiologic
  • Female
  • Humans
  • Male
  • Middle Aged
  • Peak Expiratory Flow Rate*
  • Predictive Value of Tests
  • Probability
  • Recurrence
  • Retrospective Studies
  • Risk Factors
  • Young Adult