The European Organization for Research and treatment of cancer approach to quality of life assessment: guidelines for developing questionnaire modules

The EORTC Study Group on Quality of Life (the Study Group) has adopted a modular approach to quality of life (QOL) assessment in cancer clinical trials. A core instrument—the QLQ-C30—has been designed to cover a range of QOL issues relevant to a broad spectrum of cancer patients. It is intended that this QLQ-C30 be supplemented by more specific subscales (modules) to assess aspects of QOL of particular importance to specific subgroups of patients. Since individual members of the Study Group were to be involved in module development, guidelines were required to standardize the module development process in order to ensure uniformly high quality across modules. These guidelines are presented in this paper. The term module is defined, the composition of modules is outlined, and the criteria used to develop modules are specified. The module development process, consisting of four phases (generation of relevant QOL issues, operationalization of the QOL issues into a set of items, pretesting the module questionnaire, and large-scale field-testing) is described in detail. Further, issues related to cross-cultural instrument development, and the need for monitoring the module development process from within the Study Group are discussed. Finally, experiences with developing two site-specific modules (i.e., for head and neck, and breast cancer), are presented and the extent to which the guidelines meet practical requirements is discussed. The guidelines appear to provide a practical tool for module construction, that can facilitate the development of a comprehensive system for assessing the QOL of cancer patients internationally.This work was supported, in part, by grants from the Dutch Cancer Society (NKI 90-A), the Imperial Cancer Research Fund (ICRF), and the Norwegian Cancer Society.     

Quality of life in elderly subjects with pain in the hip or knee

This study examines the quality of life (QOL) of community living elderly people aged 55-74 with chronic, episodic or sporadic pain in the hip or knee and of a reference group without pain (total n=306). Firstly, it was hypothesized that the experienced QOL is lower in people with more chronic pain. Secondly, the potential mediating and moderating roles of disability and of coping with problems in general on the relationship between pain chronicity and QOL were assessed. A Visual Analogue Scale was used to assess global QOL. Physical as well as psychosocial disability was assessed with the Sickness Impact Profile (SIP). Coping with problems in general was assessed with the Utrecht Coping List. As expected, a significantly lower QOL was found in people with more chronic pain (p=0.045). The difference in QOL between the group with chronic pain and a reference group without pain was 10%. A multivariate regression model showed that physical and especially psychosocial disability are mediators in the relationship between pain chronicity and QOL and that seeking social support as a coping style is a more important predictor of the experienced QOL than either pain chronicity or physical disability. No moderating role of the style of coping with problems was found.     

Assessment of quality of life in later life: Development and validation of the QuiLL

The aim was to develop a quality of life (QOL) instrument, informed by older people, carers and professionals in older peoples services, for use by community care staff as part of their assessment, care-planning and outcome monitoring procedures. The multi-phase development project involved: qualitative interviews to generate the item pool; pre-testing; preliminary field-testing; and final testing in a community survey and in health and social care settings. The process was informed by over 100 interviews with older people, carers, professionals, academics and policy-makers. Two products emerged following data-reduction: a research instrument (64 items), and a shorter assessment tool suitable for routine use in clinical, therapeutic or case-management practice (27 items, taking 7–15 min to complete). A community survey using the research instrument achieved a 71 response rate (n=249). Ninety six percent of people found the domain content of the assessment tool relevant, and 80 considered the items covered were important. Both instruments have good internal consistency (=0.85). Inter-rater reliability was good for research staff, but poor between them and operational staff. Little objective change took place during the 3-month follow-up study, but where it did the direction was consistent with subjective change. The instrument needs to be applied in different contexts to assess interventions of known impact. Together with daily living and health status measures it can form part of a comprehensive assessment for older people.     

Appraisal assessment in patient-reported outcome research: methods for uncovering the personal context and meaning of quality of life

Background

Recent work on patient-reported outcomes (PROs) focuses on precise, brief measures, which generally convey little about what an individual’s rating actually means. Individual differences in appraisal are important and relevant to PRO research. This paper highlights the advantages of integrating appraisal assessment into clinical research.

Methods

The most comprehensive method for assessing appraisal, the quality of life (QOL) Appraisal Profile, includes open-ended and multiple choice questions to assess four appraisal parameters: frame of reference, sampling of experience, standards of comparison, and combinatory algorithm. We illustrate with empirical findings four classes of investigation that would benefit from appraisal assessment: methodological, interpretation of change, the backstory of resilience, and clinical applications.

Results

A methodological investigation of HIV/AIDS patients revealed a range of cognitive schemas induced by the then-test response shift detection method, only 15% of which reflected the presumed process invoked. In this same study and in a study of people with multiple sclerosis (MS), interpretation of change in positive versus negative mental-health response shifts was characterized by different appraisal processes. In studying resilience in MS patients, patients with more reserve-building activities were more likely to use appraisals that emphasized the positive and more controllable aspects of their illness experience, as compared to lower-reserve patients. In underserved cancer patients, the QOL Appraisal Profile was used as a clinical interview to articulate current concerns and for personalized treatment decision-making to reduce burden and promote adherence.

Conclusions

Integrating appraisal assessment can provide a more textured, person-centered understanding of person-factors not captured by standard PROs.

     

A descriptive analysis of quality of life using patient-reported measures in major depressive disorder in a naturalistic outpatient setting

Purpose

Major depressive disorder (MDD) negatively impacts different aspects of an individual’s life leading to grave impairments in quality of life (QOL). We performed a detailed analysis of the interaction between depressive symptom severity, functioning, and QOL in outpatients with MDD in order to better understand QOL impairments in MDD.

Methods

This cross-sectional study was conducted with 319 consecutive outpatients seeking treatment for DSM-IV-diagnosed MDD at an urban hospital-based outpatient clinic from 2005 to 2008 as part of the Cedars-Sinai Psychiatric Treatment Outcome Registry, a prospective cohort study of clinical, functioning, and patient-reported QOL outcomes in psychiatric disorders using a measurement-based care model. This model utilizes the following measures: (a) Depressive symptom severity: Quick Inventory of Depressive Symptomatology-Self Report (QIDS-SR); (b) Functioning measures: Global Assessment of Functioning (GAF), Sheehan Disability Scale (SDS), Work and Social Adjustment Scale, and the Endicott Work Productivity Scale; and (c) Quality of Life measure: Quality of Life, Enjoyment, and Satisfaction Questionnaire—Short Form (Q-LES-Q).

Results

QOL is significantly impaired in MDD, with a mean Q-LES-Q score for this study population of 39.8 % (SD = 16.9), whereas the community norm average is 78.3 %. Regression modeling suggested that depressive symptom severity, functioning/disability, and age all significantly contributed to QOL. QIDS-SR (measuring depressive symptom severity), GAF, and SDS (measuring functioning/disability) scores accounted for 48.1, 17.4, and 13.3 % (semi-partial correlation values) of the variance in Q-LES-Q, respectively.

Conclusions

Our results show that impairment of QOL increases in a monotonic fashion with depressive symptom severity; however, depression symptom severity only accounted for 48.1 % of the QOL variance in our patient population. Furthermore, QOL is uniquely associated with measures of Functioning. We believe these results demonstrate the need to utilize not only Symptom Severity scales, but also Functioning and Quality of Life measures in MDD assessment, treatment, and research.     

Evaluation of point-of-care PRO assessment in clinic settings: integration,parallel-forms reliability,and patient acceptability of electronic QOL measures during clinic visits

Purpose

Assessment of patient-reported outcomes (PROs), such as health-related quality of life, has become an important component of healthcare that measures the impact of disease and medical treatment on patient health. Collecting PROs during point-of-care assessments and integrating them into the clinical setting, however, remains challenging. The objective of this pilot study was to evaluate the reliability, usability, and acceptability of point-of-care electronic PRO assessments implemented in a prostate cancer clinic.

Methods

Fifty subjects completed paper–pencil and computerized formats of the Expanded Prostate Cancer Index Composite (EPIC), a validated, condition-specific QOL instrument, at separate times before treatment. Parallel-forms reliability was evaluated by comparing mean scores, variations in response distribution, and correlations between administration formats. Correlation coefficients of at least 0.70 were used for reliability testing. Differences between administration forms, indicating potential bias, were compared using the signed-rank test. A 6-item acceptability scale was also used to evaluate patient acceptability and satisfaction with the electronic format.

Results

Mean scores and standard deviations were similar between the paper–pencil and electronic forms across all EPIC instrument domains, and no assessment bias was found. Each EPIC domain demonstrated a high reliability between administration formats (correlation coefficients: 0.70–0.98). The majority (>90 %) of respondents found that the computerized QOL format was user friendly and simple to use.

Conclusions

Point-of-care computerized QOL assessments were reliable and acceptable to patients in this study, supporting the feasibility of PRO integration at the point-of-care in clinical settings.

     

How much do doctors use quality of life information in primary care? Testing the Trans-Theoretical Model of behaviour change

This study aimed to find out whether General Practitioners (GPs) use quality of life (QOL) information in primary care, to explore their reasoning and to assess any barriers to use. A second purpose was to see whether the Trans-Theoretical Model (TTM) of behaviour change could be applied to doctors use of QOL information in primary care. A representative, cross-sectional sample of 800 GPs was approached in a national postal survey; 280 (38%) provided qualitative and quantitative information. Most GPs said that QOL was interesting and important. Users had seen more information and scales, and were more aware of its uses; only 8% had ever used formal standardised questionnaires. The main barriers to implementation were a shortage of time and information, and experience with using QOL assessment. A sizable minority wanted to know more. Seventy-one percent would use QOL to monitor treatment effectiveness. The five stages of the TTM were used to identify whether GPs were predisposed to use QOL information from their knowledge levels and values. While there was some support for the model, the TTM did not sensitively and reliably discriminate between users and non-users on all variables, and so has limited value here.     

Biological pathways,candidate genes,and molecular markers associated with quality-of-life domains: an update

Background

There is compelling evidence of a genetic foundation of patient-reported quality of life (QOL). Given the rapid development of substantial scientific advances in this area of research, the current paper updates and extends reviews published in 2010.

Objectives

The objective was to provide an updated overview of the biological pathways, candidate genes, and molecular markers involved in fatigue, pain, negative (depressed mood) and positive (well-being/happiness) emotional functioning, social functioning, and overall QOL.

Methods

We followed a purposeful search algorithm of existing literature to capture empirical papers investigating the relationship between biological pathways and molecular markers and the identified QOL domains.

Results

Multiple major pathways are involved in each QOL domain. The inflammatory pathway has the strongest evidence as a controlling mechanism underlying fatigue. Inflammation and neurotransmission are key processes involved in pain perception, and the catechol-O-methyltransferase (COMT) gene is associated with multiple sorts of pain. The neurotransmitter and neuroplasticity theories have the strongest evidence for their relationship with depression. Oxytocin-related genes and genes involved in the serotonergic and dopaminergic pathways play a role in social functioning. Inflammatory pathways, via cytokines, also play an important role in overall QOL.

Conclusions

Whereas the current findings need future experiments and replication efforts, they will provide researchers supportive background information when embarking on studies relating candidate genes and/or molecular markers to QOL domains. The ultimate goal of this area of research is to enhance patients’ QOL.     

Quality of life in low-income patients with metastatic prostate cancer: Divergent and convergent validity of three instruments

Few studies have evaluated Quality Of Life (QOL) among low-income patients with cancer. Information is needed about the feasibility and psychometric characteristics of QOL instruments in these populations. The purpose of this study was to examine the convergent and discriminant relationships between scales of three QOL instruments: European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC), Functional Assessment of Cancer Therapy – General (FACT), and Quality of Life Index (QLI). Participants included 110 men with metastatic prostate cancer of whom 94% were low income and 62% were African-American. Interviewers administered the questionnaires. Cronbach internal consistency reliabilities were 0.57 to 0.90 for the EORTC, 0.65 to 0.86 for the FACT, and 0.63 for the QLI. Convergent validity was supported for the EORTC and FACT scales measuring emotional, physical, and role/functional dimensions (r = 0.54 to 0.72), but not on scales measuring social function (r = 0.12). Divergent validity was supported between dissimilar scales (r = 0.14 to 0.38). Analysis with receiver operating characteristics curves provided empirical support for the EORTC and FACT as multidimensional measures. These findings suggest that, even in busy clinical settings with low literacy patients, interviewer-administered EORTC and FACT QOL instruments can provide valid and reliable information.     

Quality of life in overweight and obese children and adolescents: a literature review

Purpose

The purpose of the study is to present a literature review on quality-of-life (QOL) assessment in overweight or obese children and adolescents in order to identify the most affected dimensions and better understand associated factors.

Methods

The ERIC, FRANCIS, MEDLINE, PsycARTICLES, PsycINFO, and Academic Search Premier databases were searched for articles reporting cross-sectional QOL studies in obese children and adolescents published in English before January 2013. The reference lists of retained articles were also screened.

Results

Among the 34 articles retained for the analysis, only three did not report lower QOL among obese youth. Clinical populations appeared to be more affected than the general population. Several variables were associated with QOL such as self-image, bullying, bodily pain, quality of food intake, physical activity, screen time, parents’ educational level, and weight status.

Conclusions

Identifying variables associated with lower QOL in obese children and adolescents offers new perspectives for prevention and care. Further research is needed to better elucidate these findings. Better understanding QOL is a key element essential for the treatment for childhood and adolescent obesity.     

Maternal quality of life in routine labor epidural analgesia versus labor analgesia on request: results of a randomized trial

Introduction

The purpose of this study was to evaluate the changes in maternal quality of life (QOL) from pregnancy to 6 weeks after delivery between routine labor epidural analgesia (EA) and pain relief on maternal request only.

Methods

\Women delivering of a singleton in cephalic presentation beyond 36?+?0 weeks’ gestation were randomly allocated to EA as a routine during labor (routine EA group), or to any kind of analgesia on request only (control group). The Short Form health survey (SF-36) was used to assess women’s QOL before randomization, and 6 weeks postpartum. Data were analyzed according to the intention to treat principle.

Results

A total of 488 women were included, and antepartum as well as postpartum SF-36 questionnaires were filled in by 356 (73.0%) women, 176 (49.4%) in the routine EA group, and 180 (50.6%) in the control group. Changes from the QOL antepartum to the QOL 6 weeks postpartum were comparable between both groups, also in the subgroup of women in the control group who gave birth without any pain medication (n?=?41, 22.8%). Maternal age and the incidence of adverse events related to EA, which were both higher in the routine EA group, had no influence on the changes in QOL. Differences in request for pain relief were comparable with other studies.

Conclusion

Routine administration of EA during labor and pain relief on maternal request only are associated with comparable changes of women’s QOL antepartum to 6 weeks postpartum.

     

Assessing Quality of Life in Adult Cancer Survivors (QLACS)

This article describes development of a quality of life measure designed to assess issues relevant to long-term cancer survivors. In-depth semi-structured interviews were conducted with 58 long-term cancer survivors to identify domains most relevant to long-term survivors ( 5 years post-diagnosis). Self-report items were developed from these interviews and administered to a second sample of 242 long-term survivors. Domains and items were selected from the item pool by a combination of factor analysis and criterion-based item selection. Five cancer-specific domains were identified (appearance concerns, financial problems, distress over recurrence, family-related distress, and benefits of cancer) along with seven generic QOL domains (negative feelings, positive feelings, cognitive problems, sexual problems, physical pain, fatigue, and social avoidance). Cronbachs was 0.72 or greater for each domain. Correlations between domain scores and criterion measures were 0.72 or higher in all but one generic domain (social avoidance), but somewhat lower on cancer-specific domains. The new multidimensional measure has good internal consistency and validity and is appropriate for comparisons between cancer and non-cancer populations, as well as long-term follow-up of cancer patients.     

Social anxiety disorder in genuine halitosis patients

Background

There is limited information about the medium to long-term health-related quality of life (QOL) in thyroid cancer patients after initial therapy and the existing studies suffer from limitations. The aim of the study was to assess the determinants of medium-term QOL after the initial therapy.

Methods

Following a total thyroidectomy, 88 thyroid cancer patients received either rhTSH or hypothyroid-assisted radioiodine ablation (RRA) using 3.7 GBq (100 mCi) of radioiodine. QOL evaluation of the patients using the validated Functional Assessment of Chronic Illness & Therapy (FACIT) was performed at the time of inclusion (t0) and later at the 9-month post-RRA (t1).

Results

83 patients were eligible for the final evaluation. Medium-term FACIT scores were not statistically different between t0 and t1 patients. All but one domain of the QOL score was similar between t0 and t1. Using a multivariate analysis, only age and immediate postoperative QOL scores were found to be determinants of the overall medium term 9-month QOL scores. Analysis showed that 'high QOL levels' (baseline and 9-month) and 'no depression', 'low anxiety levels', were associated with '<45yrs', 'men', 'partner', and 'rhTSH stimulation'.

Conclusions

The use of radioiodine ablation does not seem to affect the medium term QOL scores of patients. Medium-term QOL is mainly determined by pre-ablation QOL. The assessment of baseline QOL might be interesting to evaluate in order to adapt the treatment protocols, the preventive strategies, and medical information to patients for potentially improving their outcomes.     

Quality of life in breast cancer patients: Validation of a FACT-B Malayalam version

Background: Recent advances in diagnosis and treatment of cancer have led to an increase in cancer survival, and hence, there is a greater emphasis on quality beside quantity of survival. Developing countries too have begun to recognize the need for monitoring quality of life (QOL). However, in most of the developing countries, a validated and reliable tool for the purpose is yet to be realized. Material and method: The functional assessment of chronic illness therapy (FACIT) system is a collection of QOL questionnaires targeted to measure QOL in chronic illness. The functional assessment of cancer therapy for breast cancer (FACT-B) was translated into the local language (Malayalam) and tested for validity and reliability. Results: The tool thus developed showed substantial sensitivity, as does the source tool. The Cronbach's for the total FACT-B was 0.87, which is similar to the of 0.9 observed in the FACT-B English version. The mean FACT-B score was 94.3 compared to 112.8 for the source tool. Conclusion: The Malayalam translation of the FACT-B questionnaire was developed, tested and validated, and was found satisfactory in comparison to the source tool.     

Changes in life-space mobility and quality of life among community-dwelling older people: a 2-year follow-up study

Purpose

Life-space mobility refers to the spatial area in which a person moves in daily life, taking into account distance, frequency and assistance needed. The aim was to examine how changes in life-space mobility are associated with changes in quality of life (QOL) over a 2-year period.

Methods

Community-dwelling people aged 75–90 years (n = 848) were interviewed face-to-face in their homes and followed up annually for 2 years. QOL was assessed with the short version of the World Health Organization QOL assessment (range 0–130, higher scores indicate better QOL). Life-space mobility was assessed with the Life-Space Assessment (range 0–120, higher scores indicate better life-space mobility). Lower extremity performance was objectively measured with the Short Physical Performance Battery (SPPB). Cognitive impairment was assessed using the Mini-Mental State Examination. Chronic conditions and years of education were self-reported. Data were analyzed with generalized estimation equation models.

Results

The mean life-space score at baseline was 63.9 ± SD 20.6 and mean QOL score 100.3 ± 11.8. Over the follow-up, the QOL score decreased to 95.0 ± 13.8 across the total study sample. The decrease in QOL score was somewhat higher among those whose life-space mobility score declined >10 points during the follow-up compared to those whose life-space remained stable or improved, even after adjustment for age, gender, number of chronic conditions, cognitive impairment, SPPB and education.

Conclusions

Decline in life-space mobility is associated with decline in QOL. The results highlight the importance of ensuring continuous possibilities for out-of-home mobility in maintaining QOL among older people.

     

Symptom prevalence,characteristics and distress in a cancer population

Despite the importance of symptom control in the cancer population, few studies have systematically assessed the prevalence and characteristics of symptoms or the interactions between various symptom characteristics and other factors related to quality of life (QOL). As part of a validation study of a new symptom assessment instrument, inpatients and out-patients with prostate, colon, breast or ovarian cancer were evaluated using the Memorial Symptom Assessment Scale and other measures of psychological condition, performance status, symptom distress and overall quality of life. The mean age of the 243 avaluable patients was 55.5 years (range 23–86 years); over 60% were women and almost two-thirds had metastatic disease. The Karnofsky Performance Status (KPS) score was80 in 49.8% and 123 were inpatients at the time of assessment. Across tumour types, 40–80% experienced lack of energy, pain, feeling drowsy, dry mouth, insomnia, or symptoms indicative of psychological distress. Although symptom characteristics were variable, the proportion of patients who described a symptom as relatively intense or frequent always exceeded the proportion who reported it as highly distressing. The mean (±SD, range) number of symptoms per patient was 11.5±6.0 (0–25); inpatients had more symptoms than outpatients (13.5±5.4 vs. 9.7±6.0, p<0.002) and those with KPS80 had more symptoms than those with KPS>80 (14.8±5.5 vs. 9.2±4.9, p<0.0001). The number of symptoms was highly associated with heightened psychological distress and poorer quality of life (for example, r=0.67 for the relationship with the Functional Living Index-Cancer, a QOL measure). These data clarify the prevalence and characteristics of cancer-related symptoms and suggest that the number of symptoms per patient may be a useful quality of life indicator.Supported by American Cancer Society Grant PRB-78 and by NIH-CA52477.     

Health-related quality of life among hemodialysis patients at El-Minia University Hospital, Egypt

Background

Hemodialysis results in significant change in daily living, physical and psychological impairments, disruption of marital, family, and social life. Health-related quality of life (HRQOL) assessment helps to plan individual treatment strategies, and determine the efficacy, quality of medical and social care provided.

Aim

The focus of the study was to assess HRQOL of hemodialysis patients attending El-Minia University Hospital dialysis unit, determine the relation between HRQOL and some sociodemograghic factors and clinical disorders and also to compare HRQOL between patients performing hemodialysis for less than and more than 5 years.

Subjects and methods

The study is a cross-sectional hospital-based study that included 170 hemodialysis patients; 81 males and 89 females, mean age 46.6?±?14.6 years. In all 59.4 % were rural residents. Data were collected by a questionnaire which included, demographic, social and medical data. Kidney Disease Quality of Life-36 (KDQOL-36) health survey was used for assessment of HRQOL.

Results

About two thirds (64 %) of the studied hemodialysis patients had physical and mental quality of life (QOL) scores below average level. HRQOL was lower in old, female, married, illiterate and non-worker hemodialysis patients. Hepatitis C positive (HCV), diabetic and anemic patients had decreased QOL scores. A longer duration of hemodialysis treatment was associated with reduced physical QOL.

Conclusion

The most important sociodemographic factors affecting HRQOL were age, sex, education, occupation and marital status. The most important clinical disorders affecting QOL were anemia, HCV infection, sleep disturbances and diabetes. Increase awareness of hemodialysis patients and their caregivers about disabilities associated with hemodialysis treatment and educational programs to decrease the problems which the patients face and to increase the QOL.     

Modification of the EORTC QLQ-C30 (version 2.0) based on content validity and reliability testing in large samples of patients with cancer

A revision of the Quality of Life Questionnaire (QLQ-C30) of the European Organization for Research and Treatment of Cancer (EORTC) was undertaken to improve low internal consistency estimates (Cronbach's alpha) and content validity for the role functioning scale and a conceptual difficulty (undue emphasis on physical functioning) in the global quality of life (QOL) scale. The role functioning items were reworded and a four-category response format was substituted for the previous dichotomous format. A new item asking about overall health was substituted for the overall physical condition item in the global QOL domain. The original and new versions were tested at three time points in a total of 1,181 patients with cancer in Canada (n=696) and the Netherlands (n=485). In both samples there was a marked improvement in internal consistency for the role functioning scale (Cronbach's alphas ranging from 0.78-0.88) in the new version. In the global QOL scale, the substitution of the new item for the previous one did not alter internal consistency (Cronbach's alphas ranging from 0.81-0.92). The revised versions of the role functioning and global QOL domains have been incorporated into the QLQ-C30 (version 2.0).     

Factor analysis, causal indicators and quality of life

Exploratory factor analysis (EFA) remains one of the standard and most widely used methods for demonstrating construct validity of new instruments. However, the model for EFA makes assumptions which may not be applicable to all quality of life (QOL) instruments, and as a consequence the results from EFA may be misleading. In particular, EFA assumes that the underlying construct of QOL (and any postulated subscales or factors) may be regarded as being reflected by the items in those factors or subscales. QOL instruments, however, frequently contain items such as diseases, symptoms or treatment side effects, which are causal indicators. These items may cause reduction in QOL for those patients experiencing them, but the reverse relationship need not apply: not all patients with a poor QOL need be experiencing the same set of symptoms. Thus a high level of a symptom item may imply that a patient's QOL is likely to be poor, but a poor level of QOL need not imply that the patient probably suffers from that symptom. This is the reverse of the common EFA model, in which it is implicitly assumed that changes in QOL and any subscales cause or are likely to be reflected by corresponding changes in all their constituent items; thus the items in EFA are called effect indicators. Furthermore, disease-related clusters of symptoms, or treatment-induced side-effects, may result in different studies finding different sets of items being highly correlated; for example, a study involving lung cancer patients receiving surgery and chemotherapy might find one set of highly correlated symptoms, whilst prostate cancer patients receiving hormone therapy would have a very different symptom correlation structure. Since EFA is based upon analyzing the correlation matrix and assuming all items to be effect indicators, it will extract factors representing consequences of the disease or treatment. These factors are likely to vary between different patient subgroups, according to the mode of treatment or the disease type and stage. Such factors contain little information about the relationship between the items and any underlying QOL constructs. Factor analysis is largely irrelevant as a method of scale validation for those QOL instruments that contain causal indicators, and should only be used with items which are effect indicators.