Untitled

Abstract

The objective of this study was to examine the structure of disease-specific quality of life (QoL). Models of QoL with either one overall construct or more constructs were tested and the relationships (factor loadings) between the constructs and dimensions were established, using structural equation modelling. The models were tested over time to assess the stability of the structure. To generalize the results further, disease-specific questionnaires of two very different chronic diseases have been compared: inflammatory bowel disease (IBD) and Parkinson's disease (PD). Questionnaires were mailed in 1994 and a repeated measurement was conducted in 1995. Data were obtained from 222 IBD patients and 235 PD patients. The results show that for both diseases, diseasespecific QoL can be considered as one construct. The stability over time of the structure of the QoL models was satisfactory. In PD the factor loadings between the dimensions and QoL were within a small range and remained the same over time, while in IBD, the factor loadings had a larger range and fluctuated more. These results imply that one meaningful sum score can be obtained from these questionnaires.Qual Life Res 7: [135][136][137][138][139][140][141][142]

Standardizing disease-specific quality of life measures across multiple chronic conditions: development and initial evaluation of the QOL Disease Impact Scale (QDIS®)

“…The strong support for a 1-factor model observed in every disease group studied is consistent with previous findings for QOL items making attributions to specific conditions [ 13 , 29 , 43 ]. It is also in sharp contrast to measurement models for generic items and scales that confirm conceptually- and empirically-distinct subdomains and higher-order physical and mental factors [ 73 , 76 ].…”

“…Standardization began with the content of the same 49 items, differing only in disease-specific attribution. Scoring of a single summary measure was based upon formal tests that confirmed a unidimensional model, consistent with previously-reported results for other disease-specific summary measures [ 13 , 29 , 43 – 45 ]. Further, the equivalence of parameters across disease groups was sufficient to justify their standardization, and very high ( r > 0.99) agreement was observed between disease-specific and standardized IRT-based score estimates.…”

“…Based on prior research [ 13 , 29 , 43 – 45 ], a 1-factor model was hypothesized and evaluated for the 49-item QDIS item bank using CFA with a robust weighted least squares (WLSMV) estimator and Mplus [ 46 ]. To test whether items were sufficiently unidimensional, the percentage of variance accounted for by one factor was estimated, and model fit was evaluated using the following criteria: comparative fit index (CFI: >0.95 indicating good fit) and root mean square error of approximation (RMSEA: <0.06 recommended, although values are often higher with large samples [ 47 ]).…”

The concept of quality of life in dementia in the different stages of the disease

“…In disease-specific research, this may lead to an emphasis on physical functioning (Smith et al, 1999). A factor analysis of disease-specific measures in Parkinson's disease and inflammatory bowel disease showed QOL to be one construct, in contrast to the multidimensional outcomes with generic measures (De Boer et al, 1998). For several generic instruments a second-order model of QOL has been demonstrated, with general QOL as the higher-order factor explaining the variance and covariance related to the first-order dimensions (see, for example, Hawthorne et al, 1999;Keller et al, 1998;Meuleners et al, 2003;Skevington et al, 2004).…”

Systematic review of neuropsychological instruments used in subthalamic nucleus deep brain stimulation in Parkinson´s disease patients

“…Only 2 scales were used for assessing PD Quality of Life (QoL): PDQ-3949 and PDQL 50. Regarding mood, several scales were used, with use of depression inventory being the most often cited 14…”