TABLE 4

Measurement properties of quality of life (QoL) tools specific for people with cystic fibrosis (CF)

Test or toolContent validityConvergent validityDiscriminant validityConcurrentPredictiveIntra- or inter-rater and test-retestInternal consistencyMeasurement errorResponsivenessComments/MCID
CFIQDemonstrated; people >6 years with CF and carers used in constructionNRNRNRNRNRNRNRNRRequires further validation; content validity established
CFQoLEasy to understand/ complete; people with CF involved in constructionCorrelation of emotional scores with SF-36 r=0.64; p<0.001Chest and emotional scores distinguished between severity of chronic lung disease (FEV1 % pred >70, 40–70 or <40)Chest score correlation with FEV1 not testedNRTest–retest rs=0.74–0.94 (p<0.01)
Robust after 7–10 days; 0.9 for emotional scores and 0.93 for respiratory
Cronbach's α=0.3NRChest symptom scores increased during pulmonary exacerbation treatment
Chest and emotional score responsive over a 2-week application period in hospital (47–70.3, p=0.006) versus home groups (49.7–68.8, p=0.03)
NR
CFQ-RPatients involved in testing clarity of items
Preschool version: children able to understand and answer questions
Correlation between CFQ-R and SF-36 on physical (r=0.81, p<0.01), health perceptions/general health (r=0.79, p<0.01), vitality (r=0.84, p<0.01), role/role-physical (r=0.73, p<0.01), emotional functioning/mental health (r=0.74, p<0.01) and social (r=0.57, p<0.01) domains
Strong convergence between child and parent proxy reports, although children generally reported better HRQoL than parents
CFQ-R: no significant difference between age groups (6–11 years, 12–13 years versus >14 years) for all domains except treatment between 6- to 11-year-olds and >14-year-olds
Significant association between CFTR genotype and CFQ-R scores (K=9.34, p<0.01)
Strong parent–child agreement found for scales measuring respiratory symptoms, but children reported more fatigue and difficulty running/walking
Respiratory score established using FEV1; correlation with FEV1 % pred r=0.42, p-value NR; correlation with number of intravenous antibiotic courses r=−0.27, p-value NRNRAcceptableCronbach's α=0.6–0.76 with the exception of treatment burden (α=0.44)
Parent proxy report for CFQ-R physical, eating and respiratory subscales α=0.73–0.86
NRBased on clinician judgement, a moderate change=0.5 units and an important change=0.8 units pre- & post- exacerbationNR
CF-QUESTNRNRNRrs was 0.951 for the total CF-QUEST score, 0.929 for gastrointestinal module and 0.941 for GHQ module for paper/electronic versionsNRNRNRNRNRExcellent correlation and agreement of electronic version with its validated paper counterpart
Patient preference tended towards electronic version
DISABKIDS-CFMNRConvergent validity with KINDL-R established; r=0.6NRNRNRNRCronbach's α=0.55 (p=0.011) for the impact dimension and 0.480 (p=0.02) for the treatment dimensionNRNRNR
FLZ-CFNRPearson's correlation r=0.75 with the generic satisfaction with health scale of the FLZ-CF, r=0.3 with FEV1 % pred and r=−0.26 with daily time for home therapy
Leisure time/hobbies, physical condition, ability to relax, energy for life and satisfaction with health rs >0.5 with positive mood and ability to relax and SF-36 physical functioning, general health, vitality, social function and mental health
The scale discriminated significantly between patients with and without need for assistance with daily life and between patients with and without a partnerPhysical condition/fitness and FEV1 % pred rs=0.66NRNRCronbach's α=0.82–0.89NRNRReliable and valid
Targets general healthy and general patient population
Short enough to be used as a screening instrument
Single item CFQoL questionnaireNRMost of the CFQoL variables were moderately correlated (r=0.38–0.61, p<0.001) with the single item scale weakly correlated with body image (r=0.25), p<0.01
Higher scores correlated negatively with frequency of hospital admissions in the previous year (r=−0.39, p<0.001)
Ability to distinguish adult CF patients with lower compared to higher CFQoL scoresSingle-item scale correlation with FEV1 r=0.21NRICC 0.78 (95% CI 0.59–0.88)NRNRNRAcceptable, valid and repeatable measurement tool that can be easily used
CQOLCFNRCorrelation with mental health r=0.634, emotional distress r=−0.687 and physical health r=0.049NRNRNRNRCronbach's α=0.909NRNRAppears to be valid, reliable and internally consistent scale

MCID: minimal clinically important difference; CFIQ: CF Impact Questionnaire; CFQoL: CF QoL Questionnaire; CFQ-R: revised CF Questionnaire; CF-QUEST: electronic version of the CFQoL evaluative self-administered test; FLZ-CF: Questions of Life Satisfaction; CQOLCF: Caregiver QoL CF scale; NR: not reported; SF-36: Short-Form-36 Item Questionnaire; HRQoL: health-related QoL; CFTR: CF transmembrane regulator; FEV1: forced expiratory volume in 1 s; GHQ: General Health Questionnaire; KINDL-R: Child QoL Questionnaire-Revised; ICC: internal consistency coefficient; rs: Spearman's correlation coefficient.