Asthma epidemiology review (February 16, 2010)

Recently-revised NIH guidelines encourage physicians to more closely monitor patients to ensure that treatments are controlling their symptoms and improving quality of life. The results has been growing interest in measures of asthma control yet relatively little work done to compare the various measures against other methods of classifying asthma. This week, JACI and ERJ published some important new articles that use data collected from therapy studies to examine asthma control and composite measures of asthma control, and their relationship to each other over time. I’ve also included a report of some surprising gender differences in the influence of socioeconomic variables on lung function decline.

Overall asthma control: The relationship between current control and future risk (E. Bateman et al. – JACI)

Very interesting retrospective analysis of five studies which examines the relationship between asthma control (assessed by questionnaire and guideline criteria) and the risk of future instability and exacerbations in asthma. Bateman and colleagues report that the percentage of patients achieving asthma control increased with time, irrespective of treatment, and not suprisingly, that asthma control score at baseline associated with exacerbation rates. In addition, the authors used Markov analysis to examine the transitional probability of change in control status throughout the studies. The finding: “A Controlled or Partly Controlled week predicted at least Partly Controlled asthma the following week (≥80% probability). The better the control, the lower the risk of an Uncontrolled week. The probability of an exacerbation was related to current state.”

Socioeconomic risk factors for lung function decline (Johannessen et al. – ERJ)

Interesting new report from a cohort study of more than 1,600 adults who performed spirometry in 1996-97 and again in 2003-6 that found gender-specific associations between different aspects of SES (socioeconomic status) and lung function decline. “Lower education and low occupational status were associated with larger male lung function decline…SES did not affect female lung function decline. However, marital status was a significant predictor; unmarried females had less decline than both married and widowed females” in both FEV1 and FVC.

Lessons learned from variation in response to therapy in clinical trials (Szefler and Martin – JACI )

“In the past, we viewed lack of response to asthma medications as a rare event. Based on recent studies, we now expect significant variation in treatment response for all asthma medications.” Szefler and Martin discuss how findings from multi-center asthma research networks (ACRN and CARE) are providing valuable new information about interindividual variability in response to a number of important controller medications. Using patient “characteristics, such as age and allergic status, and biomarkers, such as bronchodilator response, exhaled nitric oxide, and urinary leukotrienes,” can help physicians predict response and “personalize asthma treatment at the time of initiating long-term control therapy.”

Measuring asthma control: a comparison of three classification systems (O’Byrne et al. – ERJ)

In this paper, O’Byrne and colleagues compared three popular methods of assessing asthma control: The Asthma Control Questionnaire (ACQ-5) and two criteria based measures from the Global Initiative for Asthma (GINA) and Gaining Optimal Asthma ControL (GOAL) study. The review analyzed data from more than 8,000 subjects in three trials of the same asthma treatments. GINA and GOAL criteria provided similar assessments of asthma control, however, the ACQ-5 “detected clinically important improvements” in a large number of patients that according to other criteria remained uncontrolled. “ACQ-5 is more responsive to change in a clinical trial setting than a categorical scale.”