Translation, validity and reliability of the Leicester cough questionnaire into Swedish in COPD

Background: Chronic cough is a common problem which causes substantial symptoms and decrease in health related quality-of-life, HRQL. The Leicester Cough Questionnaire, LCQ is a valid evaluation tool for HRQL in patients with chronic cough. Currently no specific cough questionnaire exists in Swedish. Aim: To translate LCQ into Swedish language and to test the validity and reliability of the Swedish version of the LCQ called LCQ-S, in patients with chronic obstructive pulmonary disease, COPD. Method: The original LCQ was translated into Swedish by a method which followed an established forward-backward procedure, including cross-cultural adaptation. LCQ-S was pretested for lingual problems, scaling and clinical properties (n= 29 patients with chronic cough). To test the final version of LCQ-S9s validity the St George9s Respiratory Questionnaire, SGRQ and the COPD Assessment test, CAT were used (n= 112 patients with COPD). To test reliability the LCQ-S was repeated (n=97). Results: The LCQ-S scores showed strong respectively moderate correlation with the CAT scores (-0,69) and the SGRQ scores (-0,55). The LCQ-S showed strong internal consistency (Cronbach9s alpha coefficient 0,97). All domains and total scores of LCQ-S had excellent test-retest reliability (ICC 2,1 >0.80). Standard error of measurement, SEM (SEM%) for the LCQ-S was 0,84 (5,15%). The smallest real difference, SRD (SRD%) was 2,33 (14,25%). A Bland Altman plot of LCQ-S scores repeated in the patients with stabile health (n=86) indicates no systemic change in the mean. Conclusion : The LCQ-S is a valid instrument to measure HRQL for chronic cough in patients with COPD and can be used in clinic settings.