From September 2004 to September 2006, we developed a randomized study to demonstrate the validity of the self-administered version of the CRQ-SAS in a group of patients diagnosed with COPD before and after treatment with lung rehabilitation or liquid oxygen.

The patients were randomized in centralized blocks by one of the authors of the questionnaire in Canada (HS). They were given either the self-administered version of the CRQ-SAS or the CRQ-IA with the questions on dyspnea domain of the standardized version. The questionnaires were administered during the first week after selection (baseline) and then after finalizing the respiratory rehabilitation program or 2 months after initiating treatment with liquid oxygen (follow-up).

The protocol was approved by the ethics committee of the hospital and all the patients signed the informed consent.

The patients were selected consecutively from among the patients usually seen in our center who had been diagnosed with COPD in accordance with the criteria of the Global Initiative for Chronic Obstructive Lung Disease (GOLD)16 who had been proposed for either a respiratory rehabilitation program or for being treated with liquid oxygen.

We included patients whose mother tongue was Spanish who were under the age of 75 with a grade of dyspnea measured by the Medical Research Council (MRC)>2.17 The patients chosen had been clinically stable without episodes of exacerbation in the last month or without changes in the previous 4 months.

Excluded from the study were those patients with reading or writing difficulties, with osteomuscular, cardiac or respiratory (other than COPD) diseases that limited their exercise capacity.

The rehabilitation program included groups of 8–10 subjects each and had a duration of 8 weeks. The patients attended rehab for 3h, 3 days a week. The program consisted of:

• 1.

  Education about the disease and the treatment, with 4 sessions directed at patients and their family members.

• 2.

  Respiratory physiotherapy including directed ventilation and bronchial drainage (if indicated) techniques, as well as relaxation techniques.

• 3.

  Muscle training, including exercises for the upper and lower extremities and the respiratory muscles. The muscles of the upper limbs were exercised with weights (initially with 500g for each limb) in 30min sessions. The weight was increased by 1kg each week until the patients reached the maximum tolerable weight. The muscles of the lower extremities were exercised with a cycle ergometer, also in 30-min sessions, with an initial load representing 60% of the maximum load reached during an incremental effort test. The load was increased depending on the tolerance of the patient. For training the respiratory muscles, 15min sessions were carried out with a threshold valve device (Threshold, Respironics, Cedar Grove, New Jersey, USA), with an initial inspiratory pressure corresponding to 30% of the maximal inspiratory pressure, with increments depending on the patient's tolerance.

The patients who complied with the criteria for home oxygen therapy with liquid oxygen18 performed a baseline 6-min walk test (6MWT), breathing room air to demonstrate the need for oxygen. Later, successive 6MWTs were done to adjust the oxygen flow necessary to reach SpO2≥90%. Patients had a break of at least 30min between tests. The degree of dyspnea was evaluated by means of the Borg scale,19 both at the beginning and end of the test.

The validation of the original version with an interviewer of this questionnaire was done in collaboration by a group of Spanish pulmonologists with the original author (GG) and was demonstrated to be valid for evaluating the HRQL in COPD patients in our setting.4,8

The CRQ includes 20 questions, distributed into 4 domains: dyspnea (5 questions), fatigue (4 questions), emotional factor (7 questions) and disease control (4 questions). The dyspnea area of the CRQ-IA is individualized, allowing the patient to choose between the 5 activities that cause him/her the most dyspnea. In follow-up testing of the CRQ, the patient evaluated his/her level of dyspnea related with said activities. The responses for each area are quantified in a 7-point Likert scale. The sum of points for each domain is divided by the number of questions, obtaining a value between 1 and 7 for each. The evaluation of the resulting HRQL ranges from 1 (maximum affectation of the HRQL) up to 7 (no affectation). A change of 0.5 points or more per area is considered the minimal clinically significant change.20

The standardized dyspnea domain includes 5 questions that evaluate 5 activities that produce respiratory difficulties in most patients with COPD:

• 1.

  Feeling emotions, such as anger or disgust.

• 2.

  Personal hygiene (bathing, showering, eating or dressing).

• 3.

  Walking.

• 4.

  Performing routine daily activities (housework, shopping, errands, grocery shopping).

• 5.

  Participating in social activities (meeting with family, friends, neighbors or groups).

The other 3 domains (fatigue, emotional factor and disease control) have the same content as in the CRQ-IA, but they are self-administered. The quantification is done in the same way as the CRQ-IA.

The transcultural adaptation of the CRQ-SAS questionnaire was only done for the dyspnea domain, as in the rest of the domains the content had not been modified from the original questionnaire. For this process, the same method was followed as for the original CRQ-IA questionnaire.4,8

The variables used in the study were expressed as the mean and interquartile range as per description.

In order to calculate the mean difference between the baseline scores, the follow-up scores and the change between them, comparing the two different questionnaires (CRQ-SAS and CRQ-IA), the non-parametric Mann–Whitney test for independent samples was used due to the fact that the variables did not follow normal distribution. These are expressed as mean difference, as well as 95% confidence interval. This test was done to rule out the differences obtained in the scores having been due to chance.

For the construct and criteria validity, Spearman's correlation coefficient was calculated for the baseline scores (cross-sectional baseline), for the follow-up scores (cross-sectional follow-up) and for the change (longitudinal), for the different areas of the CRQ (SAS and IA), the SF-36 and the 6MWT.

To compare the sensitivity to changes of the CRQ-SAS and the CRQ-IA, the Wilcoxon test for paired samples was used. The results are expressed as means and 95% confidence interval. A change of 0.5 points or more, per area, was considered the minimal clinically significant change.20

All the analyses were done using the SPSS statistical program, version 15.0 (SPSS Inc., Chicago, IL, USA).

We developed the CRQ-SAS in order to facilitate its administration and comparison between different situations and patient groups. In previous studies,14,15 the CRQ-SAS shows adequate construct and criteria validity, with an expected but small reduction in the sensitivity to changes compared with the CRQ-IA. Likewise, in the study by Holger et al.15 it was demonstrated that the self-administered version of the dyspnea domain of the CRQ-SAS improves the criteria validity, maintains the construct validity but reduces the sensitivity to changes compared with CRQ-IA. The German version of the CRQ-SAS, like this present study, only analyzed the construct validity. The authors demonstrated a better longitudinal construct validity for the CRQ-SAS, represented by greater correlations between the scores for change of the CRQ and those of other instruments of validation.14 In our study, we observed good correlations for the scores of change with all the areas of the CRQ-SAS and only with the physical component of the SF-36, but not with the 6MWT.

Our study demonstrates higher correlations between the scores of change of the CRQ-SAS with the changes in the other validation instruments compared with those of the CRQ-IA. Once again, the CRQ-SAS presents a better longitudinal construct validity than the CRQ-IA. These results indicate that the standardization of the dyspnea domain does not compromise said validity.

It was observed that the individualized questions of the dyspnea domain showed a greater sensitivity to changes in the CRQ-IA than the standardized questions of the CRQ-SAS. These results are similar to our previous studies.12 One possible explanation for this fact would be that with CRQ-IA, the patients choose the activities that cause them dyspnea. Therefore, the patients may be more alert to the changes in these activities after treatment, more than to the changes produced in the standard activities of the CRQ-SAS, which probably are not are not familiar to them.

The main limitation of the use of the individualized dyspnea questions is that they make comparisons among populations difficult. However, they are closer to the daily activity of the patients.

The sensitivity to changes in the other domains was superior for the CRQ-SAS compared with the CRQ-IA. One possible explanation would be that it was due to the sample size or simply to chance.

In summary, the Spanish version of the CRQ-SAS shows a moderate validity and a good sensitivity to changes, particularly for the areas of fatigue and emotional factor. However, although the sensitivity to changes for CRQ-SAS is clearly acceptable, in the individualized area of dyspnea of the CRQ-IA the sensitivity is higher.

Given our results, our opinion is that researchers should choose the CRQ version depending on the sample size with which they are working. For studies with extensive series, it would be preferable to choose the CRQ-SAS due to the fact that it is self-administered because the CRQ-IA requires a trained interviewer, despite both tools demonstrating equally excellent properties for measurement over time. Perhaps the optimal situation would be to use the CRQ-SAS but, for the individualized dyspnea domain, use the CRQ-IA given its greater sensitivity to changes, keeping in mind that comparisons could not be made between populations or treatments in the area of dyspnea, although they could in other domains.

In conclusion, the Spanish version of the CRQ-SAS is valid for evaluating the HRQL of COPD patients. The correlations with other instruments provide construct and criteria validity, as well as good sensitivity to changes.