Objective: This study examined the factor structures and reliabilities of the Asthma Control Test (ACT) and the Asthma Control Questionnaire (ACQ-7; ACQ-6) and the correspondence between them in assessing both level and change in asthma control. Methods: Lung function and questionnaire data for ACT and ACQ were assessed in 113 asthma patients at the beginning (T1) and the end (T2) of inpatient rehabilitation. Confirmatory factor analyses, composite reliability coefficients, Pearson correlations, Cohen’s Kappa and positive/negative agreements were computed. Results: Unidimensional factor structure was confirmed for ACT. For ACQ configural invariance (i.e. same factor structure) over time could not be established. Furthermore, in ACQ-7, FEV1 showed no relation to the latent factor. Reliability estimates were 0.86–0.88 (ACT), 0.88–0.92(ACQ-6) and 0.81–0.86 (ACQ-7). Pearson correlations between ACT and ACQ were between 0.75 and 0.90 and tended to be higher at T2. If the aim is to identify patients wit...

Asthma Control Test and Asthma Control Questionnaire: factorial validity, reliability and correspondence in assessing status and change in asthma control.

Purpose: Many methods have been developed to evaluate dry powder inhalation techniques and their efficiency for disease control in asthma patients. However, it is difficult to apply these methods to clinical practice and research. In this study, we introduce a simple new method that can be applied to dry powder inhalation techniques to evaluate their efficiency in clinical practice. Methods: Twenty volunteers were recruited to evaluate the reliability of this new method. One hundred one asthma patients who met the inclusion criteria participated in this study. A dark cloth covered the outlet of the inhaler during dry powder inhalation. The image formed by the inhalation process was evaluated using analysis software and converted into integrated optical density (IOD). Inhalation techniques were scored before and after inhalation technique training, and asthma control was evaluated using the Asthma Control Questionnaire (ACQ) before inhalation technique training. Results: The relative standard devi...

A New Quantitative Method for Evaluating Dry Powder Inhalation Efficiency in Asthma Patients

Background The Asthma Control Questionnaire (ACQ) is used to assess asthma symptom control. The relationship between the questionnaire items and symptom control has not been fully studied in severe asthmatic patients, and its validity for making comparisons between subgroups of patients is unknown. Methods Data was obtained from patients in the United Kingdom Severe Asthma Registry whose symptom control was assessed using the five-item ACQ (ACQ5) (n = 2,951). Confirmatory factor analysis determined whether a latent factor for asthma symptom control, as measured by the ACQ5, was consistent with the data. Measurement invariance was examined in relation to ethnicity, sex and age; this included testing for approximate measurement invariance using Bayesian Structural Equation Modelling (BSEM). The fitted models were used to estimate the internal consistency reliability of the ACQ5. Invariance of factor means across subgroups was assessed. Results A one-factor construct with residual correlations for the ACQ5 was an excellent fit to the data in all subgroups (Root Mean Square Error Approximation 0.03 [90%CI 0.02,0.05], p-close fit 0.93, Comparative Fit Index 1.00, Tucker Lewis Index 1.00}. Expected item responses were consistent for Caucasian and non-Caucasian patients with the same absolute level of symptom control. There was some evidence that females and younger adults reported wakening more frequently during the night than males and older adults respectively with the same absolute level of symptom control (p<0.001). However approximate measurement invariance was tenable and any failure to observe strong measurement invariance had minimal impact when comparing mean levels of asthma symptom control between patients of different sexes or ages. Average levels of asthma symptom control were lower for non-Caucasians (p = 0.001), females (p<0.01)and increased with age (p<0.01). Reliability of the instrument was high (over 88%) in all subgroups studied. Conclusion The ACQ5 is informative in comparing levels of symptom control between severe asthmatic patients of different ethnicities, sexes and ages. It is important that analyses are replicated in other severe asthma registries to determine whether measurement invariance is observed.

An examination of factorial invariance of the Asthma Control Questionnaire among adults with severe asthma

Purposes
To demonstrate the assessment of measurement invariance property in a health status instrument and to increase the awareness of its importance, we evaluate the measurement invariance of the Asthma Control Questionnaire (ACQ) across age and gender subgroups.

/pdf/use-of-factor-analysis-models-to-evaluate-measurement-5ln5ehhrsf.pdf

Use of factor analysis models to evaluate measurement invariance property of the Asthma Control Questionnaire (ACQ)

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Use of factor analysis models to evaluate measurement invariance property of the Asthma Control Questionnaire (ACQ)