Individual validity of patient reported outcomes: The use of the Clinical COPD Questionnaire (CCQ) in primary care
Jan Willem Herman Kocks, Department of general practice, University Medical Center Groningen
4 December 2009
Individual validity of patient reported outcomes: The use of the Clinical COPD Questionnaire (CCQ) in primary care
JWH Kocks, T. van der Molen
Department of General practice, University Medical Center Groningen, Groningen, The Netherlands
JWH Kocks – j.w.h.kocks@med.umcg.nl – corresponding author T van der Molen – t.van.der.molen@med.umcg.nl
Abstract Response to Ställberg et al. Health and Quality of Life Outcomes 2009,7:26
Dear Editor,
With great interest we have read the article by Ställberg and colleagues[1] describing the validation of the Clinical COPD Questionnaire (CCQ) in primary care. As developer (TvM) and researcher (JWHK) of the CCQ we like to thank the authors for performing a study so relevant for clinical practice, but also like to comment on two essential results and interpretations by the authors. The authors use a different approach than commonly to determine the stability of the patient reported outcomes (test-retest reliability). Based on statistical analyses alone the authors conclude that the CCQ reliability might not be sufficient for individual patient monitoring.
The test-retest reliability is assesed using the St. George’s respiratory questionnaire (SGRQ) as indication for stability. The authors state in the discussion that they choose a long time- interval of: ??? to determine the test-retest reliability. A long time-interval indeed minimizes the problem of recall bias[2], but adds difficulty determining the stability using the intra class coefficient. The authors choose an other widely used health status questionnaire to determine change. The use of the SGRQ as method to determine stability raises two issues: 1. the cut off point of 4 points as the minimal clinically important difference is mainly based on the effectiveness of medication in a one year trial, which may not be sufficient bases to use it as a stability measure[3] and 2. The timeframe on which SGRQ “stability” was determined is “lately” as the authors describe in their methods. We suggest for future studies the use of the commonly used Global Rating of Change scale (GRC) in a shorter timeframe.
The authors state that the CCQ’s reliability may not be sufficient for the monitoring of individual patients. The result of the crohbach’s alpha (0.85) and the intra class coefficient (0.85) found in the study are indeed below the suggested threshold of 0.9 for individual monitoring. In previous studies the crohnbach’s alpha and the ICC’s of the CCQ were higher 0.89 to 0.99[4,5]. In the previous paragraph we already discussed the validity of the method to determine the ICC. Taken this into account to our opinion the authors can therefore not justify the conclusion on the individual patient monitoring in this specific study. Next to the statistical grounds, we previously proposed a new method to determine the individual validity of patient reported outcomes[6]. In short, we suggest to determine the concordance between the patient score and an in-depth interview with the patient. We performed a study using this method for the CCQ and the concordance (Lin’s concordance correlation confident (CCC)) in 44 patients was 0.88 (submitted). These results together with the feasibility to use in routine practice, we suggest the CCQ can be used in monitoring individual patients next to clinical trials and quality of care monitoring.
Authors contributions JWHK and TvdM have written this letter together.
Reference List
1. Stallberg B, Nokela M, Ehrs PO, Hjemdal P, Jonsson EW: Validation of the clinical COPD Questionnaire (CCQ) in primary care. Health Qual Life Outcomes 2009, 7: 26. 2. Stull DE, Leidy NK, Parasuraman B, Chassany O: Optimal recall periods for patient-reported outcomes: challenges and potential solutions. Curr Med Res Opin 2009, 25: 929-942. 3. Schunemann HJ, Griffith L, Jaeschke R, Goldstein R, Stubbing D, Guyatt GH: Evaluation of the minimal important difference for the feeling thermometer and the St. George's Respiratory Questionnaire in patients with chronic airflow obstruction. J Clin Epidemiol 2003, 56: 1170-1176. 4. Damato S, Bonatti C, Frigo V, Pappagallo S, Raccanelli R, Rampoldi C et al.: Validation of the Clinical COPD questionnaire in Italian language. Health Qual Life Outcomes 2005, 3: 9. 5. Molen van der T, Willemse BW, Schokker S, Ten Hacken NH, Postma DS, Juniper EF: Development, validity and responsiveness of the Clinical COPD Questionnaire. Health Qual Life Outcomes 2003, 1: 13. 6. van der Molen T, Kocks JW: Do health-status measures play a role in improving treatment in chronic obstructive pulmonary disease? Expert Opin Pharmacother 2006, 7: 57-61.
Competing interests
Competing interests The authors declare no competing interests. TvdM, with others, has developed the Clinical COPD Questionnaire.
Individual validity of patient reported outcomes: The use of the Clinical COPD Questionnaire (CCQ) in primary care
4 December 2009
Individual validity of patient reported outcomes: The use of the Clinical COPD Questionnaire (CCQ) in primary care
JWH Kocks, T. van der Molen
Department of General practice, University Medical Center Groningen, Groningen, The Netherlands
JWH Kocks – j.w.h.kocks@med.umcg.nl – corresponding author
T van der Molen – t.van.der.molen@med.umcg.nl
Abstract
Response to Ställberg et al. Health and Quality of Life Outcomes 2009,7:26
Dear Editor,
With great interest we have read the article by Ställberg and colleagues[1] describing the validation of the Clinical COPD Questionnaire (CCQ) in primary care. As developer (TvM) and researcher (JWHK) of the CCQ we like to thank the authors for performing a study so relevant for clinical practice, but also like to comment on two essential results and interpretations by the authors. The authors use a different approach than commonly to determine the stability of the patient reported outcomes (test-retest reliability). Based on statistical analyses alone the authors conclude that the CCQ reliability might not be sufficient for individual patient monitoring.
The test-retest reliability is assesed using the St. George’s respiratory questionnaire (SGRQ) as indication for stability. The authors state in the discussion that they choose a long time- interval of: ??? to determine the test-retest reliability. A long time-interval indeed minimizes the problem of recall bias[2], but adds difficulty determining the stability using the intra class coefficient. The authors choose an other widely used health status questionnaire to determine change. The use of the SGRQ as method to determine stability raises two issues: 1. the cut off point of 4 points as the minimal clinically important difference is mainly based on the effectiveness of medication in a one year trial, which may not be sufficient bases to use it as a stability measure[3] and 2. The timeframe on which SGRQ “stability” was determined is “lately” as the authors describe in their methods. We suggest for future studies the use of the commonly used Global Rating of Change scale (GRC) in a shorter timeframe.
The authors state that the CCQ’s reliability may not be sufficient for the monitoring of individual patients. The result of the crohbach’s alpha (0.85) and the intra class coefficient (0.85) found in the study are indeed below the suggested threshold of 0.9 for individual monitoring. In previous studies the crohnbach’s alpha and the ICC’s of the CCQ were higher 0.89 to 0.99[4,5]. In the previous paragraph we already discussed the validity of the method to determine the ICC. Taken this into account to our opinion the authors can therefore not justify the conclusion on the individual patient monitoring in this specific study. Next to the statistical grounds, we previously proposed a new method to determine the individual validity of patient reported outcomes[6]. In short, we suggest to determine the concordance between the patient score and an in-depth interview with the patient. We performed a study using this method for the CCQ and the concordance (Lin’s concordance correlation confident (CCC)) in 44 patients was 0.88 (submitted). These results together with the feasibility to use in routine practice, we suggest the CCQ can be used in monitoring individual patients next to clinical trials and quality of care monitoring.
Authors contributions
JWHK and TvdM have written this letter together.
Reference List
1. Stallberg B, Nokela M, Ehrs PO, Hjemdal P, Jonsson EW: Validation of the clinical COPD Questionnaire (CCQ) in primary care. Health Qual Life Outcomes 2009, 7: 26.
2. Stull DE, Leidy NK, Parasuraman B, Chassany O: Optimal recall periods for patient-reported outcomes: challenges and potential solutions. Curr Med Res Opin 2009, 25: 929-942.
3. Schunemann HJ, Griffith L, Jaeschke R, Goldstein R, Stubbing D, Guyatt GH: Evaluation of the minimal important difference for the feeling thermometer and the St. George's Respiratory Questionnaire in patients with chronic airflow obstruction. J Clin Epidemiol 2003, 56: 1170-1176.
4. Damato S, Bonatti C, Frigo V, Pappagallo S, Raccanelli R, Rampoldi C et al.: Validation of the Clinical COPD questionnaire in Italian language. Health Qual Life Outcomes 2005, 3: 9.
5. Molen van der T, Willemse BW, Schokker S, Ten Hacken NH, Postma DS, Juniper EF: Development, validity and responsiveness of the Clinical COPD Questionnaire. Health Qual Life Outcomes 2003, 1: 13.
6. van der Molen T, Kocks JW: Do health-status measures play a role in improving treatment in chronic obstructive pulmonary disease? Expert Opin Pharmacother 2006, 7: 57-61.
Competing interests
Competing interests
The authors declare no competing interests. TvdM, with others, has developed the Clinical COPD Questionnaire.