Reliability and valididty of the Chronic Respiratory Disease Questionnaire. Martin LL. Validity and reliability of a quality-of-life instrument. The chronic respiratory disease questionnaire. Clin Nurs Res ;
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For this reason, it is important to evaluate the outcomes of various interventions to ensure that patients are receiving the most efficient and best available care. Recently, clinicians and payers are recognizing that physiological measures do not necessarily relate to function, and functional outcomes need to be measured independently.
HRQL is commonly assessed through self or interviewer administered questionnaires, and may be discriminative evaluating cross-sectional differences between patients at a single point in time or evaluative measuring longitudinal changes within patients over a period of time. This paper describes the current research regarding the reliability, validity, responsiveness, minimally clinical important difference, and suggested use of the Chronic Respiratory Disease Questionnaire in clinical practice.
Based on these interviews, items were rated on their importance and grouped into 1 of 4 categories: dyspnea, fatigue, emotional function, and mastery, or a feeling of control over the disease.
Items within the dyspnea domain varied extensively, so the developers of the tool individualized this section, requesting patients to determine the 5 most important activities in their life that are affected by dyspnea. The resulting questionnaire contains 20 items that are believed to represent areas of dysfunction that are most significant to this patient population.
All questions were pretested to finalize structure and wording. Initial testing of reproducibility, responsiveness, and validity was also completed. Subsequent versions of the test have been developed to improve time and ease of administration.
All subsequent versions were developed in coordination with the original author, 7 , 8 and psychometric properties were evaluated and compared to the original CRQ. The use of any format of the CRQ does require a license agreement.
In studies of the CRQ, mean patient age has typically been reported around 67 years; 3 , 11 , 12 however, patients as young as 35 have been studied. Each domain includes 4 to 7 items, with each item graded on 7-point Likert scale; item scores within a domain are summated to provide a total score for each domain. The 4 domains are scored separately and can illustrate changes in individual domains of HRQL.
The original interviewer administered CRQ requires 20 to 25 minutes for the first administration and 10 to 15 minutes for each follow up visit. According to the office of the developer, written communication, October, using the CRQ-IAS, in which the dyspnea section is also standardized, reduces the administration time to 8 minutes.
The self administered CRQ is a written version of the tool that the patient completes independently; the wording, content, structure and scoring are exactly consistent with the original version. Furthermore, with a standardized dyspnea scale, the time to complete the questionnaire ranged from 5 to 8 minutes. Reliability, or reproducibility, can be determined in 3 ways: intra-rater, inter-rater, and test-retest. Test-retest reliability of the CRQ has been found to be high.
Guyatt et al 2 the authors of the CRQ, established the test-retest reliability of the tool prior to its release. They administered the questionnaire 6 times in a 2-week interval to 25 patients with stable COPD. They found that mean scores were similar in all 4 domains over all administrations, and there did not appear to be a tendency for either improvement or decline. From these results, the researchers concluded that the CRQ has excellent reliability.
Martin 11 found high test-retest reliability for only 3 of the 4 domains of the CRQ. Pearson correlation coefficients were used to determine consistency over time of both individual item scores and domain total scores. Individual item scores were examined using the Kendall tau correlation coefficient. In the dyspnea and mastery domains, only one item was found to lack significant correlation over time.
In the emotional function domain, 2 of the 7 items were found to lack significant correlation. In the fatigue domain, which was not reliable as a whole, 3 of the 4 individual items showed insignificant correlation.
Harper et al 13 also examined CRQ measurements in clinically stable patients over time. He found no evidence of bias in either the initial 6 month period or a second 6 month period. Lower correlation scores were noted in the second 6 month period; however, they were not significant enough to indicate that bias existed between assessments. Wijkstra et al 10 found that the internal consistency of the dyspnea domain to be much lower than the other 3.
ICCs of short term reliability ranged from 0. This degree of test-retest reliability has been shown for both the individualized and standardized forms of the CRQ. The limited availability of literature regarding intra-rater and inter-rater reliability indicates the need for further research in these areas.
The evidence has shown that the CRQ is a valid tool to assess health related quality of life in patients with chronic respiratory disease.
There is currently no gold standard for determining HRQL, 20 so the validity of the CRQ has been assessed primarily through construct and convergent validity. Construct validity was maximized during the original development of the questionnaire by using a multistep process to determine and incorporate the significant aspects of HRQL that are affected by pulmonary disease.
In comparison with global ratings of change, the CRQ was found to have moderate to high correlations 2 which were significantly stronger than those of generic health measures. Guyatt et al 21 determined that the CRQ dyspnea domain had a correlation of 0. Both the mastery and emotional domains were found to be moderately correlated with the global rating of dyspnea with r values of 0.
Functional measures were also well correlated with CRQ change scores. Singh et al 5 reported improvements in the treadmill endurance test were correlated to improvements in the CRQ total score and improvements in the domain scores of dyspnea, fatigue, and mastery. Fatigue domain scores also improved as shuttle walk test scores improved. Six minute walk test scores, however, were found to be only weakly correlated with all domains of the CRQ.
Correlations of 0. The CRQ also correlates well with generic measures. Wijkstra 10 determined that significant correlations exist between the CRQ fatigue domain and the depression and somatisation domain of the Symptom Checklist 90 SCL Other domains of the CRQ including emotion and mastery significantly correlated with somatisation, anxiety, and depression domains of the SCL However, correlations between the CRQ and other specific measures of pulmonary disease were found to be significantly higher than correlations with generic measures.
Validity was determined to be strong; no statistically significant difference between the 2 instruments was found in the fatigue and mastery domains, and the small mean differences found in the dyspnea 0. Although the authors determined that the self-administered version of the CRQ perceives analogous levels of mastery, emotional function, and fatigue, they state that the different versions of the test should not be used interchangeably. The validity of the CRQ is strengthened by the study performed by Shawn et al 14 which found statistically significant differences in CRQ scores between patients who had a relapse of their pulmonary condition and those who did not.
Further, Harper et al 13 reported that CRQ scores remained stable over time in clinically stable patients while CRQ scores improved in patients who were expected to have clinical improvements.
There was good agreement between the predicted and actual correlations in both these cases. In a study by Redelmeier et al, 24 CRQ score differences were also found to be moderately correlated with subjective comparison ratings made by patients regarding themselves and others.
The evidence has shown the CRQ to be a valid test of HRQL, with moderate to strong correlations with global ratings as well as both generic and disease specific convergent measures. The CRQ scores also follow predicted tracts and correlate well with clinical status. The fact that correlations with physiologic measures are not strong suggests that HRQL instruments such as the CRQ may provide additional information that should be used alongside physiologic tests in determining the health status of a patient.
When less responsive tools are used, it is likely that the treatment effects can be underestimated. In both studies, the CRQ was used to evaluate patients who were predicted to improve with initiation or modification of treatment.
In the first assessment, the tool was administered to 13 patients all diagnosed with chronic lung disease and the patients were then reassessed 2 to 6 weeks later after treatment had been initiated.
The developers found that the CRQ scores at the follow-up assessment were, to a large extent, better than at the initial distribution of the questionnaire, even though spirometry values were only slightly improved. This indicates that the CRQ was able to detect the change in patient condition that occurred with treatment.
In the second responsiveness assessment, the developers administered the CRQ in conjunction with other questionnaires. Twenty-eight patients with chronic lung disease received initial and follow-up questionnaires 2 weeks later after treatment had been initiated. Again, considerable improvements in the scores were seen in all domains of the original version.
Consistently, the CRQ has been shown to be more responsive than other measures. Guyatt et al 2 found that the CRQ has similar responsiveness to the Transitional Dyspnea Index and superior responsiveness to the Rand dyspnea questionnaire, the oxygen cost diagram, and the Rand physical and emotional function questionnaires.
In fact, Guyatt et al 20 demonstrated that the dyspnea domain of the CRQ was the only HRQL instrument that showed statistically significant responsiveness when tested over 2 known interventions in reducing dyspnea in day-to-day activities.
The total domain and the emotion domain scores were determined to be the most responsive to these changes. Puhan et al 12 used standardized response means SRMs to assess the responsiveness of the CRQ opposed to the t-test because it is independent of sample size.
In comparison to the other domains, the dyspnea domain had larger SRMs indicating that this individual dyspnea domain was more responsive than the other domains, and the standardized dyspnea domain was determined to be more responsive than the preference-based and generic tools that were also assessed in the study. Aaron et al 14 used the responsiveness statistic to assess the sensitivity.
From these results, the researchers concluded that the CRQ was responsive across all domains for detecting short-term changes. These lower baseline scores and greater sensitivity of the self-report questionnaire can be attributed to the fact that patients are more likely to report the severity of the impairment when asked to fill out the questionnaire in private, as opposed to being asked by the interviewer. Williams et al 26 used standardized response means to assess the sensitivity and also found the CRQ-SR to be highly sensitive across all domains of the questionnaire indicating that it is able to detect changes following a treatment program.
They also found that the baseline scores for the self-reported test were significantly lower across all domains than for the interviewer-administered questionnaire. Minimally clinically important difference MCID is a resource available to gauge if a patient deems intervention effective or not. This property can also aid researchers when gathering resources to conduct studies by enabling them to calculate appropriate sample sizes. Other useful means of the measure are interpreting studies that show significant findings and improvement of expressing results.
The 3 studies included: 31 patients participating in an inpatient pulmonary rehabilitation program, a trial examining effects of inhaled salbutamol and oral theophylline in 24 patients, and a trial of digoxin in 20 patients with heart failure. After their second visit, patients from each study were asked to report global ratings of change in shortness of breath on daily activities, level of fatigue, and emotional status.
A mean change per question of 0. One hundred twelve patients participated in the study. When all 4 of the domains were included, the MCID was 0. The researchers estimated that on average, scores on the CRQ needed to change by about 0.
Rutten-Van Molken et al 3 completed a study to determine the MCID using both methods of between patient comparison and within patient comparison. He also found that the MCID correlated with a change of 0.
Wyrwich et al 15 used triangulation methods to identify clinically important differences based on both patient and primary care provider PCP perceived differences. Patients were administered the CRQ before pulmonary rehab and again every 2 months after baseline.
The PCPs assessed the patients at baseline and at all follow-up visits throughout the year. They were also contacted following each office visit. The researchers found that according to the patient, a point decrease in a specific domain score of the CRQ reflected small declines in HRQL, and that according to both patients and PCPs, a point increase on the domain scores of the CRQ reflected a small, but clinically important improvement in HRQL.
The expert panel recommended that MCID be associated with a change greater than 2 points in the domain score. In general, patient determined clinically important differences were associated with smaller changes in CRQ domain scores than those determined by the expert panel and PCPs.
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