Reliability and factor analysis of the Spanish version of the asthma control test

The Asthma Control Test (ACT) has been developed to evaluate asthma control and to reflect its nature. A Spanish version of the test has been widely disseminated to physicians, but it has not yet been validated.

To examine the psychometric properties of the Spanish version of the ACT.

A total of 322 asthmatic patients with a mean (SD) age of 43.8 (17.3) years (range, 12-84 years) with appropriate criteria for inclusion completed the ACT. Spirometric variables were measured and asthma severity was rated by physicians.

Internal consistency reliability was 0.79. The ACT showed weak correlation coefficients with forced expiratory volume in 1 second (FEV1) (p = 0.27; P = .01) and asthma severity (p = -0.19; P = .01). Almost 40% of patients with an FEV1 less than 60% of predicted rated their asthma as well or totally controlled; conversely, 70% of patients with asthma well or totally controlled showed an FEV1 less than 80% of predicted. The factor analysis revealed a 2-factor solution: the first component included the 5 items of the ACT (subjective component), and the second component included the spirometric measures (objective component). The 2-factor solution accounted for 66.2% of the total variance.

These data reveal a unidimensional structure of the ACT and do not support the use of this test without spirometry in the management of asthma. Spirometry provides important complementary information about asthma severity that may be used in conjunction with clinical assessments of controlto provide optimal management in many patients.