Chronic Respiratory Questionnaire

The CRQ is divided into the four domains of fatigue, emotional function, mastery and dyspnoea. Patients answer to each of the 20 questions on a seven points scale expressing the degree of disability from 1 (maximum impairment) to 7 (no impairment). The standardised dyspnoea domain comprises five items concerning activities that cause shortness of breath in some patients with COPD as previously described.[18,19] When applicable we trained all interviewers in the use of this instrument in identical fashion to ensure consistent application following the recommendations of the developer of the original CRQ (GHG).

Translation and instrument development

We followed a sequential forward and backward translation approach (applied in patient group 1) (see figure ​figure11).[20] Two translators independently translated the English interviewer administered CRQ (CRQ-IA) and self-administered CRQ (CRQ-SA) as well as the individual and standardised dyspnoea items into German. In a Consensus Meeting with the translators, two pulmonologists and a methodologist agreed on first German versions for these formats. We then pilot tested these versions in 10 patients of group 1 to identify difficulties in understanding. In addition, we tested various possible wordings of items, answer choices and instructions if the translation team considered more than one possible version. An English translator with experience in biomedical sciences but unaware of the original English CRQ performed a back translation of the German CRQ formats into the source language (English). A team of McMaster University investigators compared the back translation with the English CRQ to check for conceptual discrepancies.

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Figure 1

Flow diagram of the development process of the German CRQ

After administration of the CRQ to an additional 23 patients in group 1, the translation team discussed the comments from these patients and decided in consensus on modifications. Finally, we recruited another 11 patients (belonging to group 1) to investigate whether these changes were appropriate.

Instrument testing

To allow comparisons between the different administration formats of the German CRQ, we validated them concurrently in two randomised studies. In the first study we randomly assigned 80 patients to either the CRQ-IA group (n = 40) or CRQ-SA group (n = 40). All patients completed the individualised and standardised dyspnoea items. To eliminate order effects we also randomised the order of administration (first individualised, then standardised or vice versa). We assessed all patients within 3 days after enrolment in any of the four rehabilitation programs.

In the second randomised study, we used the same randomisation procedure and included 38 stable patients (group 3). These patients completed the CRQ twice, ten days apart. These patients were blinded to their previous scores at the follow-up interview and did not undergo any therapy changes.

We generated two separate randomisation lists by computer (one for group 2 and one for group 3) in blocks of four per centre. Allocation of patients to either the CRQ-IA or CRQ-SA was concealed using a central telephone system. The site investigators, who were unaware of details on block randomisation, contacted the study coordinator (MP) by telephone for each patient who had given informed consent to receive the group assignment. The study coordinator registered the patient's initials, gender and date of birth to verify if all patients were allocated correctly. All local ethics committees approved the study protocol and patients provided informed consent prior to participation in the study.

Validation instruments to assess cross-sectional validity of the CRQ

Patients performed a six-minute walking test to assess functional exercise capacity at the beginning and end of the rehabilitation. In addition, we used a modified Borg scale in German[21] to assess the intensity of perceived dyspnoea at the end of the six-minute walking test. The Borg scale consisted of a scale labelled from 0 to 10 and with verbal descriptors. Zero represented "no dyspnoea at all" and 10 "very, very severe dyspnoea". We used two additional instruments to assess HRQL: The German self-administered SF-36 Health Survey[22] and the Feeling Thermometer (FT). The SF-36 is a generic instrument for assessment of HRQL and assesses 8 subscales of HRQL. Other investigators used the SF-36 in trials with COPD patients participating in respiratory rehabilitation.[23] The FT is an anchor based visual analogue scale from 0 to 100 where 0 (dead) represents the worst and 100 (full health) the best health state. Accumulating evidence suggests that the FT works well as a HRQL instrument in various groups of patients, including patients with COPD [24-26]. All these outcome measures were taken at the same time as the CRQ administration, i.e. at the beginning and end of the rehabilitation.

Internal consistency and cross-sectional validity (group 2)

Nine patients did not complete the study for the following reasons: five withdrew for non-specified reasons (one patient in CRQ-IA group and four in CRQ-SA group) and two patients did not meet the a priori inclusion criteria upon review of their baseline data (one patient in each group with FEV₁/FVC > 70%). In addition, two patients of the CRQ-SA group discontinued the rehabilitation program shortly after admission (one patient had an acute exacerbation requiring inpatient care and the other went home shortly after beginning of the rehabilitation). We excluded these two patients because we had decided a priori to include only patients with complete validation data in the analysis. The baseline characteristics of these two patients did not differ from the included patients. Thus, we analysed data from 38 patients of the CRQ-IA group and 33 patients of the CRQ-SA group. The patients of the two groups (CRQ-IA and CRQ-SA) were similar at baseline: Mean age was 67.4 years (SD 8.7) in the CRQ-IA and 67.7 (SD 8.3) in CRQ-SA group, FEV1/FVC predicted was 48.5% (SD 13.3) in the CRQ-IA and 49.9% (SD 10.5) in the CRQ-SA group and the average smoking history was 44.9 pack years (26.1) in the CRQ-IA and 46.8 (27.6) in the CRQ-SA group.

Crohnbach's alpha for baseline data were between 0.73 and 0.89 for both administration formats and met our a priori defined requirements for adequate internal consistency reliability (table ​(table2).2). For the CRQ-IA, corrected item-total correlations for baseline data were for all but one item above 0.32 (table ​(table3).3). Item 9 ("How often during the last two weeks have you felt embarrassed by your coughing or heavy breathing?") had a very low item-total correlation of -0.03. If this item was deleted internal consistency reliability would be markedly improved (0.86). Corrected item-total correlations tended to be higher for the CRQ-SA (0.37–0.85). As for the CRQ-IA item 9 showed the lowest corrected item-total correlation but was considerable higher compared with the CRQ-IA (0.37).

Correlations with other validation measures were generally higher for the standardised dyspnoea questions compared to the individualised questions and for the self-administered compared to the interviewer-administered dyspnoea questions, respectively (table ​(table4).4). The correlations of the CRQ-SA dyspnoea domain with the FT, the SF-36 Mental Health and Vitality Index were higher than those of the CRQ-IA.

For the fatigue domain, the correlations were similar for the CRQ-IA and CRQ-SA except for the correlations with the six-minute walking test, which was significant higher for the CRQ-IA (table ​(table5).5). We did not observe statistically significant differences between the CRQ-IA and CRQ-SA for the correlations of the emotional function and mastery domain.