BACKGROUND: The aim was to evaluate data quality and psychometric properties of an instrument for measurement of health-related quality of life: DISABKIDS Chronic Generic Module (DCGM-37) used in school-aged children with cancer.

METHODS: All school-children diagnosed with cancer in Sweden during a two-and-a-half year period were invited to participate in the study. Analysis was performed on combined data from two assessments, two and-a-half and five months after start of cancer treatment (n = 170). The instrument was examined with respect to feasibility, data quality, reliability and construct and criterion-based validity.

RESULTS: Missing items per dimension ranged from 0 to 5.3 percent, with a majority below three percent. Cronbach's alpha values exceeded 0.70 for all dimensions. There was support for the suggested groupings of items into dimensions for all but six of the 36 items of the DCGM-37 included in this study. The instrument discriminated satisfactorily between diagnoses reflecting treatment burden.

CONCLUSIONS: The results indicate satisfactory data quality and reliability of the DCGM-37 when used in children undergoing treatment for cancer. Evaluation of construct validity showed generally acceptable results, although not entirely supporting the suggested dimensionality. Continued psychometric evaluation in a larger sample of children during and after treatment for cancer is recommended.

Background

It has become important to measure long-term effects and quality of life in survivors of childhood cancer. The Minneapolis- Manchester Quality of Life (MMQL) instrument has been proven to better capture the quality of life (QoL) perspective of health than other instruments. The instrument has age appropriate versions and is therefore favourable for longitudinal studies of QoL of children surviving from cancer. The aim of this study was to evaluate the psychometric properties of the Swedish version of MMQL-Youth Form and the Adolescent Form focusing on: 1) face and content validity 2) the internal consistency and 3) the test-retest reliability.

Methods

The sample consisted of 950 pupils (11–16 years old) from 7 schools in the western Sweden who completed the questionnaire. For the test-retest evaluation 230 respondents completed the questionnaire two weeks later.

Results

Face and content validity was supported and internal consistency was found to be acceptable for the total scale for both the MMQL-Youth Form (8–12 years of age) and the Adolescent Form (13–20 years of age). Test-retest reliability for the MMQL-Youth Form was moderate for 50% of the items and good for the remaining. For the MMQL-Adolescent Form the test-retest showed moderate or good agreement for 80% of the items and fair for 20%.

Conclusions

The result indicated that the Swedish version of the MMQLYouth Form and Adolescent Form was valid and reliable in a sample of healthy children in a Swedish context. It is recommended to test the instrument among diverse samples of children such as survivors of childhood cancer in order to validate its usefulness in research and clinical settings.

BACKGROUND: Unambiguous interpretation of ordered rating scale response categories requires distinct meanings of category labels. Also, summation of item responses into total scores assumes equal intervals between categories. While studies have identified problems with rating scale response category functioning there is a paucity of empirical studies regarding how respondents interpret response categories. We investigated the interpretation of commonly used rating scale response categories and attempted to identify distinct and roughly equally spaced response categories for patient-reported rating scales in Parkinson's disease (PD) and age-matched control subjects.

METHODS: Twenty-one rating scale response categories representing frequency, intensity and level of agreement were presented in random order to 51 people with PD (36 men; mean age, 66 years) and 36 age-matched controls (14 men; mean age, 66). Respondents indicated their interpretation of each category on 100-mm visual analog scales (VAS) anchored by Never--Always, Not at all--Extremely, and Totally disagree--Completely agree. VAS values were compared between groups, and response categories with mean values and non-overlapping 95% CIs corresponding to equally spaced locations on the VAS line were sought to identify the best options for three-, four-, five-, and six-category scales.

RESULTS: VAS values did not differ between the PD and control samples (P = 0.286) or according to educational level (P = 0.220), age (P = 0.220), self-reported physical functioning (P = 0.501) and mental health (P = 0.238), or (for the PD sample) PD duration (P = 0.213) or presence of dyskinesias (P = 0.212). Attempts to identify roughly equally spaced response categories for three-, four-, five-, and six-category scales were unsuccessful, as the 95% CIs of one or several of the identified response categories failed to include the criterion values for equal distances.

CONCLUSIONS: This study offers an evidence base for selecting more interpretable patient-reported rating scale response categories. However, problems associated with raw rating scale data, primarily related to their ordinal structure also became apparent. This argues for the application of methodologies such as Rasch measurement. Rating scale response categories need to be treated with rigour in the construction and analysis of rating scales.

Background: The Locomotor Capabilities Index (LCI) is a validated measure of lower-limb amputees' ability to perform activities with prosthesis. We have developed the LCI Swedish version and evaluated its validity and reliability. Methods: Cross-cultural adaptation to Swedish included forward/backward translations and field testing. The Swedish LCI was then administered to 144 amputees (55 women), mean age 74 (4093) years, attending post-rehabilitation prosthetic training. Construct validity was assessed by examining the relationship between the LCI and Timed "Up-and-Go" (TUG) test and between the LCI and EQ-5D health utility index in 2 subgroups of 40 and 20 amputees, respectively. Discriminative validity was assessed by comparing scores in different age groups and in unilateral and bilateral amputees. Test-retest reliability (1-2 weeks) was evaluated in 20 amputees (14 unilateral). Results: The Swedish LCI showed good construct convergent validity, with high correlation with the TUG (r = -0.75) and the EQ-5D (r = 0.84), and discriminative validity, with significantly worse mean scores for older than younger and for bilateral than unilateral amputees (p < 0.01), and high internal consistency (Cronbach alpha 0.95). In test-retest reliability the intraclass correlation coefficient was 0.91 (95% CI 0.79-0.96) but for the unilateral amputees was 0.83 (95% CI 0.56-0.94). Ceiling effect occurred in 23%. Conclusion: The Swedish version of the LCI demonstrated good validity and internal consistency in adult amputees. Test-retest reliability in a small subsample appears to be acceptable. The high ceiling effect of the LCI may imply that it would be most useful in assessing amputees with low to moderate functional abilities.

BACKGROUND: The Nottingham Health Profile index of Distress (NHPD) has been proposed as a generic undimensional 24-item measure of illness-related distress that is embedded in the Nottingham Health Profile (NHP). Data indicate that the NHPD may have psychometric advantages to the 6-dimensional NHP profile scores. Detailed psychometric evaluations are, however, lacking. Furthermore, to support the validity of the generic property of outcome measures evidence that scores can be interpreted in the same manner in different diagnostic groups are needed. It is currently unknown if NHPD scores have the same meaning across patient populations. This study evaluated the measurement properties and cross-diagnostic validity of the NHPD as a survey instrument among people with Parkinson's disease (PD) and peripheral arterial disease (PAD).

METHODS: Data from 215 (PD) and 258 (PAD) people were Rasch analyzed regarding model fit, reliability, differential item functioning (DIF), unidimensionality and targeting. In cases of cross-diagnostic DIF this was adjusted for and the impact of DIF on the total score and person measures was assessed.

RESULTS: The NHPD was found to have good overall and individual item fit in both disorders as well as in the pooled sample, but seven items displayed signs of cross-diagnostic DIF. Following adjustment for DIF some aspects of model fit were slightly compromised, whereas others improved somewhat. DIF did not impact total NHPD scores or resulting person measures, but the unadjusted scale displayed minor signs of multidimensionality. Reliability was > 0.8 in all within- and cross-diagnostic analyses. Items tended to represent more distress (mean, 0 logits) than that experienced by the sample (mean, -1.6 logits).

CONCLUSION: This study supports the within- and cross-diagnostic validity of the NHPD as a survey tool among people with PD and PAD. We encourage others to reassess available NHP data within the NHPD framework to further evaluate the strengths and weaknesses of this simple patient-reported index of illness-related distress.