Quality of life in the Danish general population--normative data and validity of WHOQOL-BREF using Rasch and item response theory models.

BACKGROUND: The main objective of this study was to investigate the construct validity of the WHOQOL-BREF by use of Rasch and Item Response Theory models and to examine the stability of the model across high/low scoring individuals, gender, education, and depressive illness. Furthermore, the objective of the study was to estimate the reference data for the quality of life questionnaire WHOQOL-BREF in the general Danish population and in subgroups defined by age, gender, and education. METHODS: Mail-out-mail-back questionnaires were sent to a randomly selected sample of the Danish general population. The response rate was 68.5%, and the sample reported here contained 1101 respondents: 578 women and 519 men (four respondents did not indicate their genders). RESULTS: Each of the four domains of the WHOQOL-BREF scale fitted a two-parameter IRT model, but did not fit the Rasch model. Due to multidimensionality, the total score of 26 items fitted neither model. Regression analysis was carried out, showing a level of explained variance of between 10 and 14%. The mean scores of the WHOQOL-BREF are reported as normative data for the general Danish population. CONCLUSION: The profile of the four WHOQOL-BREF domains is a more adequate expression of quality of life than the total score of all 26 items. Although none of the subscales are statistically sufficient measures of their domains, the profile scores seem to be adequate approximations to the optimal score.

The internal and external validity of the Major Depression Inventory in measuring severity of depressive states.

BACKGROUND: We have developed the Major Depression Inventory (MDI), consisting of 10 items, covering the DSM-IV as well as the ICD-10 symptoms of depressive illness. We aimed to evaluate this as a scale measuring severity of depressive states with reference to both internal and external validity. METHOD: Patients representing the score range from no depression to marked depression on the Hamilton Depression Scale (HAM-D) completed the MDI. Both classical and modern psychometric methods were applied for the evaluation of validity, including the Rasch analysis. RESULTS: In total, 91 patients were included. The results showed that the MDI had an adequate internal validity in being a unidimensional scale (the total score an appropriate or sufficient statistic). The external validity of the MDI was also confirmed as the total score of the MDI correlated significantly with the HAM-D (Pearson's coefficient 0.86, P < or = 0.01, Spearman 0.80, P < or = 0.01). CONCLUSION: When used in a sample of patients with different states of depression the MDI has an adequate internal and external validity.

The sensitivity and specificity of the Major Depression Inventory, using the Present State Examination as the index of diagnostic validity.

BACKGROUND: A self-rating inventory has been developed to measure DSM-IV and ICD-10 diagnoses of major (moderate to severe) depression by the patients' self-reported symptoms. This Major Depression Inventory (MDI) can be scored both according to the DSM-IV and the ICD-10 algorithms for depressive symptomatology and according to severity scales by the simple total sum of the items. METHODS: The Schedule for Clinical Assessment in Neuropsychiatry (SCAN) was used as index of validity for the clinician's DSM-IV and ICD-10 diagnosis of major (moderate to severe) depression. The sensitivity and specificity of MDI was assessed in a sample of 43 subjects covering a spectrum of depressive symptoms. RESULTS: The sensitivity of the MDI algorithms for major depression varied between 0.86 and 0.92. The specificity varied between 0.82 and 0.86. When using the total score of MDI the optimal cut-off score was estimated 26 and the total score was shown to be a sufficient statistic. LIMITATIONS: The sample of subjects was limited. Patients with psychotic depression were not included. CONCLUSION: The MDI was found to have a sensitivity and specificity which is acceptable. The questionnaire is brief and can be scored diagnostically by the DSM-IV and ICD-10 algorithms as well as by its simple total score.

Fatigue in the Danish general population. Influence of sociodemographic factors and disease.

OBJECTIVE: To measure the levels of fatigue in the general population, and to examine how disease and sociodemographic factors influence fatigue. DESIGN: Cross sectional questionnaire study in the Danish general population. SUBJECTS: A random, age stratified sample of 1608 people aged 20-77 with an equal gender distribution (response rate 67%). MAIN OUTCOME MEASURES: Five fatigue scales from the questionnaire Multidimensional Fatigue Inventory: General Fatigue, Physical Fatigue, Reduced Activity, Reduced Motivation and Mental Fatigue. RESULTS: Fatigue scores were skewed towards absence of fatigue. The General Fatigue and Physical Fatigue scales showed the highest fatigue levels while the Reduced Motivation scale showed lowest levels. Gender differences in fatigue scores were small, but the variability among women was higher-that is, more women had high scores. A multiple linear regression analysis showed that respondents of low social status and respondents with a depression had high fatigue scores on all scales, independent of other factors. Chronic somatic disease had an independent direct effect on Mental Fatigue, but for the rest of the scales, the effect of somatic disease depended on age, gender and/or whether the person was living alone. For example, General and Physical Fatigue decreased with age among healthy people, whereas scores on these scales increased with age among those with a somatic disease. CONCLUSIONS: Physical and mental diseases play essential parts for the level of fatigue and as modulators of the associations between sociodemographic factors and fatigue. These interactions should be taken into account in future research on fatigue and sociodemographic factors and when data from clinical studies are compared with normative data from the general population.