Design and baseline characteristics of the epidemiology and natural history of asthma: Outcomes and Treatment Regimens (TENOR) study: a large cohort of patients with severe or difficult-to-treat asthma

Ann Allergy Asthma Immunol. 2004 Jan;92(1):32-9. doi: 10.1016/S1081-1206(10)61707-3.


Background: Patients with severe and difficult-to-treat asthma represent a small percentage of asthma patients, yet they account for much of the morbidity, mortality, and cost of disease. The goal of The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens (TENOR) study is to better understand the natural history of asthma in these patients.

Objective: To describe the methods and baseline characteristics of the TENOR study cohort.

Methods: The TENOR study is a 3-year, multicenter, observational study of patients with severe or difficult-to-treat asthma. From January through October 2001, more than 400 US pulmonologists and allergists enrolled patients. Patients 6 years or older who were considered to have severe or difficult-to-treat asthma by their physicians were eligible. Patients have been receiving care for 1 year or more, have a smoking history of 30 pack-years or less, and have current high medication or health care utilization in the past year. Data are collected semiannually.

Results: A total of 4,756 patients enrolled and completed a baseline visit. Overall, 73% of the TENOR study patients are adults, 10% are adolescents, and 16% are children. According to physician evaluation, 48% of patients have severe asthma, 48% have moderate asthma, 3% have mild asthma, and 96% have difficult-to-treat asthma. Severe asthmatic patients have the highest health care utilization in the past 3 months (P < .001).

Conclusions: The TENOR study is the largest cohort of patients with severe or difficult-to-treat asthma. Although patients are equally divided into moderate or severe asthma categories, most are considered difficult-to-treat. The TENOR study highlights the lack of control in moderate-to-severe asthma and provides a unique opportunity to examine factors related to health outcomes in this understudied population.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Anti-Asthmatic Agents / therapeutic use*
  • Asthma / drug therapy
  • Asthma / epidemiology*
  • Asthma / physiopathology*
  • Child
  • Delivery of Health Care
  • Demography
  • Disease Management
  • Female
  • Health Surveys*
  • Humans
  • Immunoglobulin E
  • Male
  • Prospective Studies
  • Research Design*
  • Respiratory Function Tests
  • Self Care
  • Severity of Illness Index
  • Surveys and Questionnaires


  • Anti-Asthmatic Agents
  • Immunoglobulin E