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.

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.