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(Chest. 2003;123:42-48.)
© 2003 American College of Chest Physicians

Questions on Life Satisfaction for Adolescents and Adults With Cystic Fibrosis*

Development of a Disease-Specific Questionnaire

Lutz Goldbeck, PhD; Tim G. Schmitz, PhD; Gerhard Henrich, PhD and Peter Herschbach, PhD

* From the University Clinic of Child and Adolescent Psychiatry/Psychotherapy (Dr. Goldbeck), Ulm; Children’s Hospital Schwabing (Dr. Schmitz), Technical University, Munich; and Institute and Outpatient Clinic for Psychosomatic Medicine (Drs. Henrich and Herschbach), Psychotherapy and Medical Psychology, Clinic Right of Isar, Munich, Germany.

Correspondence to: Lutz Goldbeck, PhD, Universitätsklinik und Poliklink für Kinder- und Jugendspsychiatrie/Psychotherapie, Steinhövelstr. 5, D89075 Ulm, Germany; e-mail: lutz.goldbeck{at}medizin.uni-ulm.de


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 References
 
Study objectives: The development and psychometric properties of an additional disease-specific module of the Questions on Life Satisfaction for adolescents and adults with cystic fibrosis (FLZM-CF) are described. The Questions on Life Satisfaction (FLZM) instrument allows the respondent to rate the subjective importance and her/his satisfaction with different domains of life.

Methods: A preliminary 16-item version of the scale was employed in a study with 243 German patients with cystic fibrosis (CF) [16 to 58 years of age; FEV1, 15 to 121% of predicted], together with the "general life satisfaction" module and the "satisfaction with health" module of the FLZM. Item elimination according to the principle of least common variance resulted in the final nine-item version.

Results: Cronbach {alpha} for the FLZM-CF was 0.80; the split-half reliability was 0.72. Convergent validity of the scale was indicated by Pearson correlations of r = 0.75 with the generic satisfaction with health scale of the FLZM, r = 0.30 with FEV1%, and r = - 0.26 with daily time for home therapy. The scale discriminated significantly between patients with and without need for assistance in daily life and between patients with and without a partner.

Conclusions: The FLZM-CF is a reliable and valid instrument, and it is short enough to be used as screening instrument. The combination of generic and disease-specific scales within the FLZM allows comprehensive measurement of life satisfaction for patients with CF who are > 15 years old.

Key Words: adolescents and adults • cystic fibrosis • disease-specific questionnaire • life satisfaction • quality of life


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 Conclusion
 References
 
Recent progress in medical treatment has prolonged life expectancy for patients with cystic fibrosis (CF) into adulthood. The median survival rate is approximately 33 years,1 and it is still increasing. Therefore, patients with CF face the same developmental hurdles as their healthy peers: detachment from their parents, graduation from school, finding a job, establishing a partnership, and integration into society.2 3 In contrast to healthy individuals, patients with CF have to cope with multiple disease-related stressors and restrictions and are required to accomplish a time-demanding therapy every day. Facing an uncertain prognosis involves permanent emotional distress; they fear a worsening of their disease, and they hope for a final cure in new therapies or successful lung transplantation.4 5 6 7

Health-related quality of life (QL) is considered as a key concept in evaluating therapy efficiency and in describing the situation of the individual patient, especially in the case of a chronic disease as CF.8 There is an ongoing discussion about different ways of measuring health-related QL in patients with CF.9 The multiple dimensions of the construct require comprehensive measures that can be expressed as QL profiles.10 As generic questionnaires allow comparisons between patients with different diseases and with healthy control subjects, disease-specific instruments might be more valid for examining the situation of patients with a chronic disease and more sensitive for changes in their health status.11 With CF patients, both generic and disease-specific questionnaires have been applied.12 13 14 15 16 17 18 19 20 21 22

Another way of measuring subjective QL is to assess life satisfaction. A generic life satisfaction instrument has been presented by Henrich and Herschbach23 (Questions on Life Satisfaction [FLZM]). The FLZM was developed as a multidimensional generic questionnaire that allows the respondent to rate her/his satisfaction with each of 16 domains of daily life in relation to the subjective importance of each domain. Eight general dimensions of life satisfaction are measured: friends/acquaintances, leisure time/hobbies, general health, income/financial security, occupation/work, housing/living conditions, family life/children and partner relationship/sexuality. Eight dimensions are health related without reference to disease-specific problems: physical condition/fitness, ability to relax, energy/zest for life, mobility, vision and hearing, freedom from anxiety, freedom from aches and pain, and independence from help/care. First, the respondent rates the subjective importance of each dimension on scales from 1 (not important) to 5 (extremely important). Second, the present satisfaction with each of these dimensions is rated, again on 5-point scales (1 = dissatisfied, to 5 = very satisfied). The weighted scores are calculated by the following formula: weighted satisfaction = (importance rating - 1) x [(2 x satisfaction rating) - 5]. Two sum scores are computed by adding the eight health-related and the eight general satisfaction scores. In a previous study, good reliability and validity of the FLZM has been reported with an adolescent and adult CF population.9 24

As the generic FLZM does not assess CF-specific aspects of life satisfaction, it was the aim of this study to develop an additional disease-specific scale of the FLZM for adolescents and adults with CF (FLZM-CF). This instrument was constructed according to the same assessment principles as the generic FLZM modules, ie, as importance x satisfaction ratings.


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 Conclusion
 References
 
The development of the FLZM-CF was an iterative process. After item generation, a preliminary version of the scale was tested. Some items were reworded to improve intelligibility, and the scale was reduced to a 16-item version. Then this version was tested in a study with 243 adolescents and adults with CF. The final 9-item version is the result of further item reduction and psychometric testing of the 16-item version. The development of the questionnaire was done in German, the final version of the FLZM-CF was then translated into English by means of independent forward-backward translations. This method guarantees semantic convergence of the German and English version of the instrument. Patients participating in the pilot study needed approximately 5 min on average to complete the 16-item version, and together with the generic FLZM modules it took up to 10 min. The questionnaire has a clear written instruction (see Appendix) and can be filled in by the patients themselves without assistance of medical staff.

Item Generation
The content validity of the items of the new instrument was established using multiple methods. In a previous study, we conducted interviews with adolescent and adult CF patients about their living circumstances and their QL.24 As a result of this study, we were able to describe specific dimensions and problems of living with CF. Additional information on CF-specific QL issues was obtained from the literature on the subject and from interviews with members of a multiprofessional team working with CF outpatients and inpatients. The format of the questions (first step, importance of a domain; second step, satisfaction with this domain) and the time frame (past 4 weeks) were assimilated to the generic FLZM modules.

Sample
With the help of the German Cystic Fibrosis Association, all 750 patients >= 16 years old being registered in the mailing list of the association were asked to participate in the study. Together with a newsletter from the association, the patients received a written explanation of the study together with the questionnaire. Two hundred forty-eight patients filled in the questionnaire at home and sent it back anonymously to the study center (response rate, 33%), together with data on their medical and social situation. Limited resources did not allow us to maximize participation by reminding the nonresponders to send back their questionnaires. Five responders < 16 years old were excluded from the study. The sample characteristics of the remaining 243 participants are demonstrated in Table 1 . Due to the indirect sampling procedure, we had to rely on self-report data on educational level, and the literacy of the participants could not be tested. The anonymous way of recruiting the participants for our study did not allow group comparisons with nonparticipating individuals. Therefore a possible self-selection bias has to be considered. We compared the medical data of our sample with the data of 1,208 patients > 17 years old from the German medical CF register25 and found similar levels of FEV1% (mean, 57.2%; SD, 25.0%), colonization with Pseudomonas aeruginosa (72.2%), and body mass index (BMI) [mean, 20.1; SD, 2.8]. Therefore, in terms of medical status, our sample can be considered representative of those CF patients in Germany who are followed up regularly by specialized outpatient clinics.


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  		Table 1.. Sample Characteristics (n = 243)

 
Statistical Procedure
Means and SDs were calculated for the importance scores, the satisfaction scores, and for the weighted scores of each item. To avoid insensitive or nonspecific items, floor and ceiling effects of the weighted dimensions were determined by examining the percentage of minimum and maximum scorers. Several statistical procedures were performed to reduce the complexity of the questionnaire without a significant loss of validity: Spearman rank intercorrelations with the items of the generic FLZM scales were computed in order to examine the degree of convergence. Items with the most common variance with the generic items and scales of the FLZM were eliminated, as the FLZM-CF was intended to represent those domains of living with CF that are not well represented in the generic scales. A factor analysis on the 12 x 12 intercorrelation matrix of the remaining items with an eigenvalue criterion > 0.5 was performed, followed by varimax rotation, to identify the "purest" items. If more than one item loaded > 0.50 on one factor, the item with the lower loading was excluded from the scale.

The reliability of the final nine-item scale was determined by Cronbach {alpha} and a split-half reliability coefficient (odd/even method). The validity of the scale was tested using Spearman correlations of the weighted sum score with the generic scales of the FLZM, with FEV1% and BMI as objective parameters of health, and with time for daily therapy as a measure of the intensity of home therapy. Additional validity tests were performed by comparing the mean scores on the new scale (t tests for independent samples, analyses of variance [ANOVAs]) of known groups (patients with and without need of assistance in daily life; patients with and without a partner; patients with FEV1 > 70%, 40 to 70%, or < 40% of the predicted; patients with their own lungs or after lung transplantation).


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 Conclusion
 References
 
The number of missing data were far below 1%, indicating good practicability and intelligibility of the questionnaire. The distribution of the weighted scores of the 16-item version indicated no relevant floor or ceiling effects. Therefore, none of the original items had to be excluded from the scale. Furthermore, item intercorrelations between the weighted scores of the FLZM-CF and the weighted scores of the generic FLZM scales were analyzed. One item (present course of the disease) was excluded due to a correlation of > 0.70—indicating > 50% common variance—with a single item of the FLZM general life satisfaction scale (present health status). Three items (freedom of traveling, activities with friends, plans for the future) were excluded due to correlations of > 0.65 with one of the total scores of the generic FLZM scales.

The factor analysis of the remaining 12 x 12-item intercorrelation matrix of the FLZM-CF led to an eight-factor solution, explaining 87% of the total variance. The scree plot revealed one main factor responsible for most of the total variance. The loading matrix of the eight-factor solution after varimax rotation is shown in Table 2 . Since we intended to reduce the scale to those items with the greatest independence from each other, we decided to eliminate all items that showed second-rank loadings on another factor (attractiveness, attachment/intimacy, and coping with the disease). The dyspnea item was not excluded because of its face validity for the situation of patients with CF, although it is obviously not independent from the items disadvantage and sleep.


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  		Table 2.. Loading Matrix of the FLZM-CF Items After Factor Analysis and Varimax Rotation*

 
Means, SDs, and percentage of minimum and maximum scorers for the total sample of 243 patients are demonstrated in Table 3 . Only items of the final nine-item version were included in this table.


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  		Table 3.. Means and SDs in the FLZM, Percentage of Minimum and Maximum Scorers, Item-Scale Correlations/Cronbach {alpha}*

 
The internal consistency of the scale is indicated by item-scale correlations of between r = 0.31 and r = 0.61, and by Cronbach {alpha} of 0.80. The split-half reliability (odd/even method) is 0.72. Cronbach {alpha} is 0.73 for the general life satisfaction scale, and 0.85 for the general health satisfaction scale.

Convergent validity of the FLZM-CF is indicated by Spearman correlations of 0.75 with the FLZM general health sum score and of 0.66 with the FLZM general life satisfaction total score (Table 4 ). Correlations of 0.30 with the FEV1% and 0.26 with the time for daily home therapy demonstrate further validity of the instrument. No significant correlations could be found between the FLZM-CF total score and BMI or age. According to the results of an ANOVA (low/medium/high educational level), no significant effect of education on the disease-specific life satisfaction could be demonstrated. With the exception of the dyspnea item (male patients were more satisfied with their freedom from dyspnea and coughing than female patients (mean difference, 3.3; t = 3.3, p = 0.001), no significant gender differences appeared in the FLZM-CF.


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  		Table 4.. FLZM Scale Intercorrelations and Correlations of the FLZM Scales With Pulmonary Function (FEV1%), BMI, and Daily Time for Home Therapy

 
Discriminant ability of the FLZM-CF could be demonstrated by mean comparisons between subgroups of patients. As expected, patients with good or sufficient pulmonary function (FEV1 >= 70%) scored significantly higher on the FLZM-CF than patients with moderate or severe restrictions (FEV1 < 70%) [mean difference, 20.1; t = 3.9, p < 0.001). Patients who had undergone heart-lung transplantation (n = 6) scored significantly higher on the FLZM-CF than patients with their own organs (mean difference, 44.0; t = 2.8, p = 0.006). Patients living in a partnership reported a higher disease-related life satisfaction than patients without a partner (mean difference, 15.2; t = 3.1, p = 0.002). Based on the self-report of the patients, we distinguished between patients without need of assistance in daily life, with some need of assistance, and with a need of permanent assistance. The ANOVA with the FLZM-CF total score as dependent variable revealed a strong significant effect of the patients’ independence from help (F = 13.6, p < 0.001).

Figure 1 displays the mean scores of the study group in the final FLZM-CF. The study participants reported the most satisfaction with their eating, with the integration of their therapy into daily routine, with their sleep, and with their freedom from abdominal complaints. They were less satisfied with experiencing disadvantage due to CF and with their pulmonary symptoms (dyspnea/cough). Medium weighted satisfaction is indicated on the dimensions being needed and being understood by others.



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  		Figure 1.. Disease-specific life satisfaction as measured by the FLZM-CF (group means, n = 243 adolescents and adults with CF). The distances from the center point indicate the weighted share of each item, the marked tract represents the total disease-specific life satisfaction within the study group.

 

   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
Conclusion
 References
 
As a combination of generic and disease-specific modules, the FLZM allow a multidimensional assessment of a patient’s satisfaction with various domains of life in relation to their subjective importance. Eight domains of general life satisfaction, eight domains of general health-related satisfaction, and nine domains of CF-related life satisfaction can be integrated into a comprehensive profile of life satisfaction. The new disease-specific scale covers a broad range of physical and psychosocial aspects of living with CF, which are not represented in generic QL instruments. The main potential benefit of the FLZM compared with other QL measures is its comprehensiveness, brevity, and the weighting procedure that allows the respondent to indicate the subjective importance of specific life domains.

The FLZM-CF has sufficient psychometric properties in terms of internal consistency and validity. Life satisfaction as a multidimensional psychological construct of subjective health only partly overlaps with parameters of objective health. Therefore the convergence between the FLZM scores and the FEV1% is limited. The low correlation between these variables may also be explained by the limited reliability of FEV1 as a measure of disease severity in CF.26 27 Further studies should investigate the external validity of the FLZM-CF by comparisons with more reliable measures of objective health and with standard measures of mental health and well-being. Due to the cross-sectional design of our study, we are not yet able to report on the sensitivity of the FLZM-CF for changes in the patients’ health status. This aspect should be investigated in longitudinal studies, for example by repeated assessment of life satisfaction with the FLZM-CF and simultaneously the assessment of pulmonary function. Moreover, sample effects in our study should be controlled for in future investigations with other CF populations. So far, we have not observed patients with difficulty answering the FLZM. It seems to be an easily applicable instrument. The high nonresponse rate in our study may be explained with the indirect and anonymous sampling procedure that excluded any personal contact between the investigator and the patient.


   Conclusion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
References
 
In summary, the results of this study indicate good practicability, reliability and construct validity of the method, although further external validation is needed. In combination with the generic modules of the FLZM, the FLZM-CF is a comprehensive and brief instrument for evaluating patients’ subjective perspectives on their lives. Software for the computer-assisted assessment with the FLZM is also available. This modification of the method increases the economy and practicability of QL assessment in clinical practice. The questionnaire can be used both for clinical and research purposes. As a screening method supplementing the conversation of the physician with the individual patient, the questionnaire could help to identify patients who need support in specific domains. As a research instrument, the questionnaire might be useful in evaluating the impact of new therapy strategies on the subjective health of patients with CF. In the future, more therapy studies examining possible adverse effects on QL are needed. If the improvement of life satisfaction is considered equally important to improving the medical status, QL assessment should become a routine procedure in clinical practice and research with CF patients.


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  		Table A1.. CF-Specific Module to the FLZM

 

   Footnotes
 
Abbreviations: ANOVA = analysis of variance; BMI = body mass index; CF = cystic fibrosis; FLZM = Questions on Life Satisfaction; FLZM-CF = disease-specific scale of the Questions on Life Satisfaction for adolescents and adults with cystic fibrosis; QL = quality of life

Received for publication November 21, 2001. Accepted for publication July 30, 2002.


   References
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 References
 

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