The German adaptation of the Cambridge pulmonary hypertension outcome review (CAMPHOR)
© Cima et al.; licensee BioMed Central Ltd. 2012
Received: 4 May 2012
Accepted: 21 August 2012
Published: 13 September 2012
Individuals with precapillary pulmonary hypertension (PH) experience severely impaired quality of life. A disease-specific outcome measure for PH, the Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR) was developed and validated in the UK and subsequently adapted for use in additional countries. The aim of this study was to translate and assess the reliability and validity of the CAMPHOR for German-speaking populations.
Three main adaptation stages involved; translation (employing bilingual and lay panels), cognitive debriefing interviews with patients and validation (assessment of the adaptation’s psychometric properties). The psychometric evaluation included 107 patients with precapillary PH (60 females; age mean (standard deviation) 60 (15) years) from 3 centres in Austria, Germany and Switzerland.
No major problems were found with the translation process with most items easily rendered into acceptable German. Participants in the cognitive debriefing interviews found the questionnaires relevant, comprehensive and easy to complete. Psychometric analyses showed that the adaptation was successful. The three CAMPHOR scales (symptoms, activity limitations and quality of life) had excellent test-retest reliability correlations (Symptoms = 0.91; Activity limitations = 0.91; QoL = 0.90) and internal consistency (Symptoms = 0.94; Activity limitations = 0.93; QoL = 0.94). Predicted correlations with the Nottingham Health Profile provided evidence of the construct validity of the CAMPHOR scales. The CAMPHOR adaptation also showed known group validity in its ability to distinguish between participants based on perceived general health, perceived disease severity, oxygen use and NYHA classification.
The CAMPHOR has been shown to be valid and reliable in the German population and is recommend for use in clinical practice.
Precapillary pulmonary hypertension (PH) consists of the WHO clinical classes 1 and 4, i.e. pulmonary arterial hypertension (PAH) and chronic thromboembolic PH (CTEPH). Despite many new therapeutic options (with the exception of patients with operable CTEPH) life expectancy is still dramatically shortened[1–3]. Hence, the search for new therapies is on-going, and multiple trials are underway or being planned. One of the main problems of planning such large trials is the absence of an ideal endpoint. Invasive haemodynamic parameters are considered to represent hard endpoints, which are optimal for phase II trials. However, it is not feasible to perform these measurements repeatedly in everyday clinical practice. Most trials now rely on the 6-minute walking distance (6MWD) as the primary endpoint. However, this test has many flaws including disagreement about the normal values, the quality with which it is conducted, high standard deviation of distances walked and large minimally important difference of over 40 meters. In reality, exercise testing does not provide an accurate reflection of how patients really feel.
As a consequence, quality of life (QoL) has emerged as a potentially important endpoint. Most clinical studies to date have used generic patient-reported outcome measures such as the SF-36[6–9], the EuroQol[9, 10] or the Nottingham Health Profile. However, generic instruments generally have a low responsiveness, particularly with PH patients. For instance, the minimally important difference of the SF-36 domains range between 13 and 25 points on a 100-point scale. This implies that scores have to improve by up to 25 points before the change is noticeable by patients. Some trials have applied a modified version of the Minnesota Living with Heart Failure (MLWHF) questionnaire[13, 14]. Although this has been shown to have a reasonable performance[15, 16] it was not designed for patients with PH.
Given the impact of PH on morbidity, comprehensive disease-specific measures that directly address PH characteristics are needed. The Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR) was designed as a disease-specific measure to assess both health-related QoL (symptoms and activity limitations) and QoL in patients diagnosed with PH. It is an evaluation tool designed for use in clinical trials and clinical practice. The present paper describes the translation and validation of the CAMPHOR for use in German speaking countries. A successful adaptation will provide a valid and reliable outcome measure for use in PH clinical practice and clinical trials at German speaking centres.
The adaptation of the CAMPHOR questionnaire was conducted in the three German-speaking countries; Austria, Germany and Switzerland. The process consisted of three main stages; translation (by means of bilingual and lay panels), cognitive debriefing interviews with patients to determine face and content validity and validation by means of a clinic visit and postal survey. Ethics committee approval was obtained from each participating centre and written informed consent was obtained from all participants.
Step 1: Translation process
The bilingual translation panel involved a group of 2 Austrian, 3 German and 4 Swiss participants (7 females and 2 males with a median age of 47 and a range of 30 to 62 years) with good competence in both English and German who had the latter as their primary language. They were asked to consider the UK CAMPHOR instructions and items with the following requirements in mind; capturing the same concepts as the UK English version and producing a comprehensible and acceptable formulation of the concepts. Each item was discussed until agreement was reached. Where consensus could not be reached alternative versions of the item were taken forward for consideration by the lay panel.
A separate lay translation panel consisted of 1 Austrian, 2 German and 3 Swiss non-bilingual participants (3 females and 3 males; median age 27 ranging from 18 to 76 years). The purpose of this second panel was to ensure that the wording of items was appropriate for future respondents with average educational achievement. Participants were presented with the translations made by the bilingual panel and asked to comment on these in terms of comprehension and acceptability. In particular, they were asked to decide whether phrasing and language were acceptable or whether these should be changed to make the items more ‘natural’ while maintaining their original meaning. Where necessary they were also asked to choose between alternative translations that the bilingual panel had produced.
Step 2: Cognitive debriefing interviews
Cognitive debriefing interview panel (n = 12)
Validation sample (n = 107)
22 − 80
Married/living as married (%)
Living alone (%)
Not working (%)
Step 3: Validation
Validation sample; disease information (n = 107)
Cause of PH
Idiopathic PAH (%)
Associated PAH (%)
Duration of PH (years)
Hospital admission in last year due to PH
6 Min Walk Test (metres)
Perceived general health
Very good/Good (%)
Very poor/ Poor (%)
Perceived severity of PH
No symptoms (%)
Very & Quite severe (%)
NYHA functional class was determined at the outpatient visit (Class 1, no functional limitation; Class 2, slight functional limitation; Class 3, marked functional limitation; Class 4, inability to perform functions without symptoms).
Patients also completed the Nottingham Health Profile (NHP;).
The CAMPHOR was then administered on two occasions by mail approximately two weeks apart.
Data are presented as means and standard deviations (SD) for illustrative purposes. Non-parametric statistical tests were used throughout the analyses due to the ordinal nature of the measures employed. All statistical tests were two-tailed with a P value of < .05 indicating statistical significance. Internal consistency of the CAMPHOR adaptations was evaluated by determining Cronbach’s alpha coefficients. The relatedness of individual items to the overall score was also assessed using the corrected item-total correlation coefficients. Test-retest reliability (patient-specific agreement between the two repeated administrations) was examined using Spearman’s rank correlations. Construct validity was assessed with the NHP as the comparator instrument.
Known-group validity (ability to distinguish between groups of patients who differed according to some known factor) was tested for:
Perceived general health (very good/good; fair; poor/very poor)
Perceived PH severity (No symptoms/mild; Moderate; Quite severe/very severe)
Oxygen use (yes / no)
NYHA class (NYHA I and II versus NYHA III and IV)
The CAMPHOR was originally developed and validated in the United Kingdom. It has subsequently been adapted for use in the US, Canada (French and English), Australia / New Zealand and Sweden. It consists of a 25-item symptoms scale (scored 0–25), a 15-item functioning scale (scored 0–30) and a 25-item QoL scale (scored 0–25). For all scales, a low score indicates a better status. All language versions have been shown to have good internal consistency, reproducibility and validity[26–28].
Nottingham Health Profile
The NHP is a 38-item measure of perceived distress that has been widely used in health research. It consists of six sections that assess; energy level, pain, emotional reactions, sleep, social isolation and physical mobility. All sections are scored 0 to 100 with a low score indicating good health status.
The NHPD is a 24-item unidimensional scale of impairment embedded in the NHP.
No major difficulties were experienced during the translation process and most items in the questionnaire were translated without difficulty. Agreement was generally reached with little panel discussion. However, a small number of phrases required more extensive discussion. For example, “glücklich” was chosen instead of “zufrieden” for “happy” since the latter was considered to be closer to “satisfied” than “happy”. “Mein Zustand belastet mich” was preferred to “Mein Zustand nimmt mich mit” for “It gets me down” because the former was thought to represent the burden of the disease better. “Zur Zeit” was favoured over “zum jetzigen Zeitpunkt” for “at the moment”, as the latter was believed to be more accurate.
Cognitive debriefing interviews
The CAMPHOR was completed in a median of 15 (range 7 to 25) minutes. Based on their responses participants found the questionnaire to be clear, unambiguous, comprehensive and easy to complete. Only minor difficulties were reported. For example, one patient had difficulty understanding one of the items and another thought that a different item was not relevant. None of the patients judged the questionnaire to be inappropriate or difficult to answer. Three patients thought that an additional item should be added to the questionnaire. Each suggested a different item and none were relevant to the content of the scales. No changes were required to the questionnaire as a result of the cognitive debriefing interviews. However, despite the instructions, only two respondents checked that they had answered all questions after completing the measure. Consequently, the instructions were highlighted in an attempt to overcome this oversight.
One-hundred and seven participants were recruited at Time 1. At Time 2, 97 of these (90.7%) completed and returned the questionnaires.
Participant details are shown in Table1. Individual country sample sizes were insufficient to permit assessment of the national psychometric properties separately and the samples were merged for the analysis. Disease information for the sample is shown in Table2.
Questionnaire descriptive scores
The missing response rate at the item level on both the CAMPHOR and NHP varied between 2 and 3%.
Questionnaire descriptive scores Time 1 (n = 107)
% scoring minimum
% scoring maximum
Internal consistency and reproducibility
Internal consistency and reproducibility of the CAMPHOR scales adaptations (n = 107)
Convergent validity CAMPHOR scales and NHP sections (n = 107)
6 Minute Walk Test (meters)
Association of CAMPHOR scores with demographic factors
There were no significant differences in mean CAMPHOR scores related to gender with the exception of the Activity limitations scale where females scored higher than males (means = 9.3 and 7.8 respectively, p < .05). Older individuals (above median age) scored higher on the Symptoms scale than younger respondents (means = 5.9 and 9.1 respectively, p < .05) and Activity limitations scale (means = 6.7 and 10.9 respectively, p < 0.001). There were no differences in CAMPHOR scale scores related to duration of PH.
Known group validity
CAMPHOR scale scores by disease factors (n = 100-102)
Perceived general health
Perceived severity of PH
No symptoms / mild
Quite / very severe
The results showed that the adaptation of the CAMPHOR for use with German speaking participants was successful. Few problems were encountered during the translation process. All participants in the cognitive debriefing panel reported that the measure was easy to complete and that it covered important aspects of their experience of PH.
All scales in the CAMPHOR had good internal consistency and reproducibility. The CAMPHOR showed expected levels of association with the different NHP sections. Further evidence of the validity of the German CAMPHOR was shown by its ability to distinguish between groups known to differ by perceived disease severity, general health and oxygen use. Importantly, clinical validity was also demonstrated; CAMPHOR scores were moderately related to the 6MWT and were able to distinguish between NYHA classifications. On the basis of these findings clinicians working in the three German-speaking nations can have confidence in CAMPHOR scale scores.
One of the strengths of the study is that it tested the CAMPHOR in 3 German-speaking countries. In all these countries written German is the same modern Standard German known as High German (Hochdeutsch). Most non-German researchers may not consider the differences between the German speaking nationalities and assume that an adaptation in one country will be suitable for all German speakers. However, the language used in the CAMPHOR is, intentionally, as informal as possible and it is possible that this could have led to differences in wording in the different countries. Variations between the German dialects are considerable and often only the neighbouring dialects are mutually intelligible. Low German, most Upper German and even some Central German dialects when spoken in their purest form are not intelligible to people who only know standard German. The German dialects of South Tyrol have been influenced by local Romance languages with many words borrowed from Italian. Furthermore, there is no standard Swiss German. Valais German differs markedly from Bernese German. Hence, adapting the CAMPHOR in relatively central cities in the three countries should guarantee a broad understandability.
The sample included in this study appeared to be less severe than those commonly included in clinical trials and in the UK validation survey. However, this study was designed to test the performance of the German CAMPHOR rather than to report on the impact of PH on QoL. Future studies can be undertaken to relate PH variables to QoL.
Increasingly, health authorities are conducting economic evaluations in health care. High-cost orphan diseases like PH are prone to careful scrutinisation. The preferred methodology is cost utility analysis (CUA) whereby the benefits of health care interventions are measured according to quality adjusted life years (QALYs). Due to their lack of sensitivity and relevance, the commonly used generic preference based measures of health status may be inappropriate for some specific clinical conditions such as PH. The CAMPHOR Utility Index embedded in the CAMPHOR QoL scale permits derivation of PH-specific utility scores. In contrast to traditional outcomes, such as NYHA functional class, 6MWD and generic QoL instruments, it has been shown to be valid and responsive to change. Further studies testing the use of the CAMPHOR utility index with German speaking PH patients would be beneficial.
In conclusion, the current study shows that the German translation of the CAMPHOR is a valid and reliable instrument for assessment of health-related QoL and QoL in patients with precapillary PH. Its use in clinical practice can be recommended.
The CAMPHOR is a copyrighted instrument that is available free of licensing fees for use by clinicians and researchers in non-commercial studies. A small administrative fee is charged for such use. Readers interested in using the CAMPHOR should contact Stephen McKenna on firstname.lastname@example.org orhttp://www.galen-research.com
1Department für Innere Medizin, Schwerpunkt Pneumologie, Universitätsklinik, Innsbruck, Austria. 2Galen Research Ltd, Manchester, UK.3Pulmonary Hypertension Program, University Hospital, Zurich, Switzerland.4Thoraxklinik, Universitätsklinikum, Heidelberg, Germany.
- Humbert M, Sitbon O, Yaïci A, Montani D, O'Callaghan DS, Jaïs X, Parent F, Savale L, Natali D, Günther S, Chaouat A, Chabot F, Cordier JF, Habib G, Gressin V, Jing ZC, Souza R, Simonneau G, French Pulmonary Arterial Hypertension Network: Survival in incident and prevalent cohorts of patients with pulmonary arterial hypertension. Eur Respir J 2010, 36: 549–55. 10.1183/09031936.00057010View ArticlePubMedGoogle Scholar
- Shapiro S, Traiger GL, Turner M, McGoon MD, Wason P, Barst RJ: Sex differences in the diagnosis, treatment, and outcome of patients with pulmonary arterial hypertension enrolled in the registry to evaluate early and long-term PAH disease management (REVEAL). Chest 2011, 141(2):363–373.View ArticlePubMedGoogle Scholar
- Condliffe R, Kiely DG, Gibbs JS, Corris PA, Peacock AJ, Jenkins DP, Hodgkins D, Goldsmith K, Hughes RJ, Sheares K, Tsui SS, Armstrong IJ, Torpy C, Crackett R, Carlin CM, Das C, Coghlan JG, Pepke-Zaba J: Improved outcomes in medically and surgically treated chronic thromboembolic pulmonary hypertension. Am J Respir Crit Care Med 2008, 177: 1122–1127. 10.1164/rccm.200712-1841OCView ArticlePubMedGoogle Scholar
- McLaughlin VV, Badesch DB, Delcroix M, Fleming TR, Gaine SP, Galiè N, Gibbs JS, Kim NH, Oudiz RJ, Peacock A, Provencher S, Sitbon O, Tapson VF, Seeger W: End points and clinical trial design in pulmonary arterial hypertension. J Am Coll Cardiol 2009, 54: S97-S107. 10.1016/j.jacc.2009.04.007View ArticlePubMedGoogle Scholar
- Benza RL, Miller DP, Gomberg-Maitland M, Frantz RP, Foreman AJ, Coffey CS, Frost A, Barst RJ, Badesch DB, Elliott CG, Liou TG, McGoon MD: Predicting survival in pulmonary arterial hypertension: insights from the Registry to Evaluate Early and Long-Term Pulmonary Arterial Hypertension Disease Management (REVEAL). Circulation 2010, 122: 164–172. 10.1161/CIRCULATIONAHA.109.898122View ArticlePubMedGoogle Scholar
- Galiè N, Olschewski H, Oudiz RJ, Torres F, Frost A, Ghofrani HA, Badesch DB, McGoon MD, McLaughlin VV, Roecker EB, Gerber MJ, Dufton C, Wiens BL, Rubin LJ: Ambrisentan for the treatment of pulmonary arterial hypertension: results of the ambrisentan in pulmonary arterial hypertension, randomized, double-blind, placebo-controlled, multicenter, efficacy (ARIES) study 1 and 2. Circulation 2008, 117: 3010–3019. 10.1161/CIRCULATIONAHA.107.742510View ArticlePubMedGoogle Scholar
- Jaïs X, D'Armini AM, Jansa P, Torbicki A, Delcroix M, Ghofrani HA, Hoeper MM, Lang IM, Mayer E, Pepke-Zaba J, Perchenet L, Morganti A, Simonneau G, Rubin LJ: Bosentan for treatment of inoperable chronic thromboembolic pulmonary hypertension: BENEFiT (Bosentan Effects in iNopErable Forms of chronIc Thromboembolic pulmonary hypertension), a randomized, placebo-controlled trial. J Am Coll Cardiol 2008, 52: 2127–2134. 10.1016/j.jacc.2008.08.059View ArticlePubMedGoogle Scholar
- Simonneau G, Rubin LJ, Galiè N, Barst RJ, Fleming TR, Frost AE, Engel PJ, Kramer MR, Burgess G, Collings L, Cossons N, Sitbon O, Badesch DB, PACES Study Group: Addition of sildenafil to long-term intravenous epoprostenol therapy in patients with pulmonary arterial hypertension: a randomized trial. Ann Intern Med 2008, 149: 521–530.View ArticlePubMedGoogle Scholar
- Galiè N, Brundage BH, Ghofrani HA, Oudiz RJ, Simonneau G, Safdar Z, Shapiro S, White RJ, Chan M, Beardsworth A, Frumkin L, Barst RJ: Tadalafil therapy for pulmonary arterial hypertension. Circulation 2009, 119: 2894–2903. 10.1161/CIRCULATIONAHA.108.839274View ArticlePubMedGoogle Scholar
- Olschewski H, Simonneau G, Galiè N, Higenbottam T, Naeije R, Rubin LJ, Nikkho S, Speich R, Hoeper MM, Behr J, Winkler J, Sitbon O, Popov W, Ghofrani HA, Manes A, Kiely DG, Ewert R, Meyer A, Corris PA, Delcroix M, Gomez-Sanchez M, Siedentop H, Seeger W: Inhaled iloprost for severe pulmonary hypertension. N Engl J Med 2002, 347: 322–329. 10.1056/NEJMoa020204View ArticlePubMedGoogle Scholar
- Barst RJ, Rubin LJ, Long WA, McGoon MD, Rich S, Badesch DB, Groves BM, Tapson VF, Bourge RC, Brundage BH, Koerner SK, Langleben D, Keller CA, Murali S, Uretsky BF, Clayton LM, Jöbsis MM, Blackburn SD, Shortino D, Crow JW, for the Primary Pulmonary Hypertension Study Group: A comparison of continuous intravenous epoprostenol (prostacyclin) with conventional therapy for primary pulmonary hypertension. The Primary Pulmonary Hypertension Study Group. N Engl J Med 1996, 334: 296–302. 10.1056/NEJM199602013340504View ArticlePubMedGoogle Scholar
- Gilbert C, Brown MC, Cappelleri JC, Carlsson M, McKenna SP: Estimating a minimally important difference in pulmonary arterial hypertension following treatment with sildenafil. Chest 2009, 135: 137–142. 10.1378/chest.07-0275View ArticlePubMedGoogle Scholar
- McLaughlin VV, Benza RL, Rubin LJ, Channick RN, Voswinckel R, Tapson VF, Robbins IM, Olschewski H, Rubenfire M, Seeger W: Addition of inhaled treprostinil to oral therapy for pulmonary arterial hypertension: a randomized controlled clinical trial. J Am Coll Cardiol 2010, 55: 1915–1922. 10.1016/j.jacc.2010.01.027View ArticlePubMedGoogle Scholar
- Simonneau G, Barst RJ, Galie N, Naeije R, Rich S, Bourge RC, Keogh A, Oudiz R, Frost A, Blackburn SD, Crow JW, Rubin LJ: Continuous subcutaneous infusion of treprostinil, a prostacyclin analogue, in patients with pulmonary arterial hypertension: a double-blind, randomized, placebo-controlled trial. Am J Respir Crit Care Med 2002, 165: 800–804.View ArticlePubMedGoogle Scholar
- Cenedese E, Speich R, Dorschner L, Ulrich S, Maggiorini M, Jenni R, Fischler M: Measurement of Quality of Life in pulmonary hypertension and its significance. Eur Respir J 2006, 28: 808–815. 10.1183/09031936.06.00130405View ArticlePubMedGoogle Scholar
- Chen H, De Marco T, Kobashigawa EA, Katz PP, Chang VW, Blanc PD: Comparison of cardiac and pulmonary-specific quality-of-life measures in pulmonary arterial hypertension. Eur Respir J 2011, 38: 608–616. 10.1183/09031936.00161410PubMed CentralView ArticlePubMedGoogle Scholar
- McKenna SP, Doughty N, Meads DM, Doward LC, Pepke-Zaba J: The Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR): A measure of health-related quality of life and quality of life for patients with pulmonary hypertension. Qual Life Res 2006, 15: 103–115. 10.1007/s11136-005-3513-4View ArticlePubMedGoogle Scholar
- ATS: Statement:guidelines for the six-minute walk test. Am J Respir Crit Care Med 2002, 166: 111–117.View ArticleGoogle Scholar
- Wilsher M, Good N, Hopkins R, Young P, Milne D, Gibson A, Suppiah R, Ly J, Doughty R, Dalbeth N: The six-minute walk test using forehead oximetry is reliable in the assessment of scleroderma lung disease. Respirology 2012, 17(4):647–652. May 10.1111/j.1440-1843.2012.02133.xView ArticlePubMedGoogle Scholar
- Goldman MD, Marrie RA, Cohen JA: Evaluation of the six-minute walk in multiple sclerosis subjects and healthy controls. Mult Scler 2008, 14(3):383–390. Apr 10.1177/1352458507082607View ArticlePubMedGoogle Scholar
- Sciurba F, Criner GJ, Lee SM, Mohsenifar Z, Shade D, Slivka W, Wise RA: National Emphysema Treatment Trial Research Group. Six-minute walk distance in chronic obstructive pulmonary disease: reproducibility and effect of walking course layout and length. Am J Respir Crit Care Med 2003, 167: 1522–1527. 10.1164/rccm.200203-166OCView ArticlePubMedGoogle Scholar
- Gomberg-Maitland M, Huo D, Benza RL, McLaughlin VV, Tapson VF, Barst RJ: Creation of a model comparing 6-minute walk test to metabolic equivalent in evaluating treatment effects in pulmonary arterial hypertension. J Heart Lung Transplant 2007, 26: 732–738. 10.1016/j.healun.2007.04.013View ArticlePubMedGoogle Scholar
- Oudiz RJ, Barst RJ, Hansen JE, Sun XG, Garofano R, Wu X, Wasserman K, et al.: Cardiopulmonary exercise testing and six-minute walk correlations in pulmonary arterial hypertension. Am J Cardiol 2006, 97: 123–126. 10.1016/j.amjcard.2005.07.129View ArticlePubMedGoogle Scholar
- The Criteria Committee of the New York Heart Association: Nomenclature and Criteria for Diagnosis of Diseases of the Heart and Great Vessels. 9th edition. Little, Brown & Co, Boston, Mass; 1994:253–256.Google Scholar
- Hunt SM, McEwen J: McKenna SP. Croom Helm, Measuring Health Status London; 1986.Google Scholar
- Gomberg-Maitland M, Thenappan T, Rizvi K, Chandra S, Meads DM, McKenna SP: United States validation of the Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR). J Heart Lung Transplant 2008, 27: 124–130. 10.1016/j.healun.2007.10.004View ArticlePubMedGoogle Scholar
- Coffin D, Duval K, Martel S, Granton J, Lefebvre MC, Meads DM, Twiss J, McKenna SP: Adaptation of the Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR) into French-Canadian and English-Canadian. Can Respir J 2008, 15: 77–83.PubMed CentralPubMedGoogle Scholar
- Ganderton L, Jenkins S, McKenna SP, Gain K, Fowler R, Twiss J, Gabbay E: Validation of the Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR) for the Australian and New Zealand population. Respirology 2011, 16: 1235–1240. 10.1111/j.1440-1843.2011.02030.xView ArticlePubMedGoogle Scholar
- McKenna SP, Hunt SM, Tennant A: The development of a patient-completed index of distress from the Nottingham Health Profile: A new measure for use in cost-utility studies. Br J Med Econ 1993, 6: 13–24.View ArticleGoogle Scholar
- McKenna SP, Ratcliffe J, Meads DM, Brazier JE: Development and validation of a preference based measure derived from the Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR) for use in cost utility analyses. Health Qual Life Outcomes 2008, 6: 65. 10.1186/1477-7525-6-65PubMed CentralView ArticlePubMedGoogle Scholar
- Meads DM, McKenna SP, Doughty N, Das C, Gin-Sing W, Langley J, Pepke-Zaba J: The responsiveness and validity of the CAMPHOR Utility Index. Eur Respir J 2008, 32: 1513–1519. 10.1183/09031936.00069708View ArticlePubMedGoogle Scholar
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