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An empirical comparison of the St George 's Respiratory Questionnaire ( SGRQ ) and the Chronic Respiratory Disease Questionnaire ( CRQ ) in a clinical trial setting . BACKGROUND The Chronic Respiratory Questionnaire ( CRQ ) and the St George 's Respiratory Questionnaire ( SGRQ ) are the two most widely used quality of life questionnaires in chronic obstructive pulmonary disease ( COPD ) . A study was undertaken to compare directly the self-administered version of the CRQ and the SGRQ with respect to feasibility , internal consistency , validity , and sensitivity to changes resulting from bronchodilator therapy . METHODS One hundred and forty four patients with moderate or severe COPD were randomly assigned to receive three months of treatment with either salmeterol , salmeterol + ipratropium bromide , or placebo . Quality of life was measured at baseline and after 12 weeks of treatment . RESULTS The proportions of missing values per patient were low for both questionnaires ( 0.54 % for the CRQ and 2 % for the SGRQ ) . The internal consistency was good for both questionnaires ( Cronbach 's alpha coefficients > /= 0.84 for the CRQ and > /= 0.76 for the SGRQ ) . Factor analysis confirmed the original domain structure of the CRQ but not of the SGRQ . Correlations with forced expiratory volume in one second ( FEV ( 1 ) ) % predicted and peak expiratory flow rate ( PEFR ) were low for both questionnaires but better for the SGRQ than for the CRQ . The ability to discriminate between subjects with different levels of FEV ( 1 ) was somewhat better for the SGRQ . The correlations with symptom scores were comparable for both questionnaires . Cross sectionally , the scores of the two questionnaires were moderately to highly correlated ( coefficients ranged from 0.35 to 0.72 ) . Longitudinally , these correlations were lower ( coefficients ranged from 0.17 to 0.54 ) but were still significant . The CRQ total and emotions score and the SGRQ symptoms score were the most responsive to change . The SGRQ symptoms domain was the only domain where the improvement in patients receiving combination treatment crossed the threshold for clinical relevance . CONCLUSIONS Since this analysis of reliability , validity , and responsiveness to change did not clearly favour one instrument above the other , the choice between the CRQ and the SGRQ can be based on other considerations such as the required sample size or the availability of reference values .
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Intervention_Pharmacological
salmeterol
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Intervention_Pharmacological
salmeterol
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Intervention_Pharmacological
ipratropium bromide
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Intervention_Control
placebo
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Outcome_Physical
Quality of life
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Outcome_Physical
proportions of missing values
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Outcome_Other
internal consistency
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Outcome_Physical
( FEV ( 1 ) ) %
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Outcome_Physical
peak expiratory flow rate ( PEFR )
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Outcome_Physical
FEV ( 1 )
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Outcome_Other
CRQ total and emotions score
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Outcome_Physical
and the
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Outcome_Other
SGRQ symptoms score
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Outcome_Physical
SGRQ symptoms domain
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Participant_Condition
( COPD ) .
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Participant_Condition
One hundred and forty four patients with moderate or severe COPD