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Abbreviated World Health Organization Quality of Life questionnaire (WHOQOL-Bref) in north Indian patients with bronchial asthma: an evaluation using Rasch analysis.

Aggarwal AN, Agarwal R, Gupta D - NPJ Prim Care Respir Med (2014)

Bottom Line: Item 3 (pain prevents doing work) displayed a large positive fit residual value (indicating violation of unidimensionality), resulting in poor construct validity for the physical domain.The modified scale had good construct validity for all domains, ordered thresholds for all items and good targeting of items to persons.However, when modified by Rasch analysis, the scale proved better than the original scale.

View Article: PubMed Central - PubMed

Affiliation: Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India.

ABSTRACT

Background: There is no disease-specific instrument to describe health-related quality of life (HRQoL) in Indian patients with asthma. However, an abbreviated World Health Organization Quality of Life questionnaire (WHOQOL-Bref), a generic Hindi HRQoL measure, has been developed and validated in India.

Aims: To evaluate the WHOQOL-Bref in adult patients with asthma and to test possible modifications to the instrument to improve its psychometric adequacy.

Methods: Sixty-seven patients with asthma completed the WHOQOL-Bref. Rasch analysis was used to explore the psychometric performance of the four domains (physical, psychological, social relationships and environment) of the scale. Overall fit of data to model expectations, appropriate category ordering, presence of differential item functioning, individual item fit and targeting of item difficulty to patient ability were explored for each domain. Item deletion and rescoring were applied to misfitting items to improve overall performance.

Results: The overall fit of the WHOQOL-Bref data was adequate. Item 3 (pain prevents doing work) displayed a large positive fit residual value (indicating violation of unidimensionality), resulting in poor construct validity for the physical domain. No item exhibited differential item functioning. Ten items had disordered thresholds. The WHOQOL-Bref was modified by dropping item 3 and rescoring category structures of 16 items. The modified scale had good construct validity for all domains, ordered thresholds for all items and good targeting of items to persons.

Conclusions: The WHOQOL-Bref performed inadequately in describing HRQoL in the asthma patients studied. However, when modified by Rasch analysis, the scale proved better than the original scale.

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Related in: MedlinePlus

Example of category probability curves. The top panel for item 12 (money to meet needs) of the abbreviated World Health Organization Quality of Life reveals disordered and reversed thresholds. There is no point on the continuum where response categories 2 or 4 are the most likely responses. Threshold locations (corresponding to points of intersection between probability curves of two adjacent response categories) between response 1 or 2 and 2 or 3, and between 3 or 4 and 4 or 5, are reversed. The bottom panel shows the curves redrawn after rescoring category structure (collapsing categories 1 and 2, and 4 and 5). After this merger, the three response categories for this item are well ordered and distributed, with persons with higher ability (or better quality of life) having a progressively greater probability of endorsing a higher response category.
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fig2: Example of category probability curves. The top panel for item 12 (money to meet needs) of the abbreviated World Health Organization Quality of Life reveals disordered and reversed thresholds. There is no point on the continuum where response categories 2 or 4 are the most likely responses. Threshold locations (corresponding to points of intersection between probability curves of two adjacent response categories) between response 1 or 2 and 2 or 3, and between 3 or 4 and 4 or 5, are reversed. The bottom panel shows the curves redrawn after rescoring category structure (collapsing categories 1 and 2, and 4 and 5). After this merger, the three response categories for this item are well ordered and distributed, with persons with higher ability (or better quality of life) having a progressively greater probability of endorsing a higher response category.

Mentions: Mean±s.d. person location estimates were satisfactory for all domains as they were not significantly different from the corresponding centralised item location means of zero logit (Table 2). This indicated that the study sample as a whole was neither located at a better level nor located at a lower level of HRQoL than the average of the scale. Therefore, overall the scale appeared well targeted for this patient group. Graphical analysis (Figure 1), as well as formal statistical testing (Supplementary Table S2 ), did not suggest significant DIF for any item. Threshold analysis showed that threshold distances between various responses to an item varied across items. Significant anomalies for threshold patterns were observed for the WHOQOL-Bref as 10 of the 24 items had disordered thresholds (see Supplementary Table S3 and Figure 2). These results suggest that the response scales of several items were inadequate in ordering patients with distinct levels of ability. Moreover, distances between adjacent thresholds were >5 logits in 8 instances and <1.4 logits in 28 instances (see Supplementary Table S3).


Abbreviated World Health Organization Quality of Life questionnaire (WHOQOL-Bref) in north Indian patients with bronchial asthma: an evaluation using Rasch analysis.

Aggarwal AN, Agarwal R, Gupta D - NPJ Prim Care Respir Med (2014)

Example of category probability curves. The top panel for item 12 (money to meet needs) of the abbreviated World Health Organization Quality of Life reveals disordered and reversed thresholds. There is no point on the continuum where response categories 2 or 4 are the most likely responses. Threshold locations (corresponding to points of intersection between probability curves of two adjacent response categories) between response 1 or 2 and 2 or 3, and between 3 or 4 and 4 or 5, are reversed. The bottom panel shows the curves redrawn after rescoring category structure (collapsing categories 1 and 2, and 4 and 5). After this merger, the three response categories for this item are well ordered and distributed, with persons with higher ability (or better quality of life) having a progressively greater probability of endorsing a higher response category.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4373256&req=5

fig2: Example of category probability curves. The top panel for item 12 (money to meet needs) of the abbreviated World Health Organization Quality of Life reveals disordered and reversed thresholds. There is no point on the continuum where response categories 2 or 4 are the most likely responses. Threshold locations (corresponding to points of intersection between probability curves of two adjacent response categories) between response 1 or 2 and 2 or 3, and between 3 or 4 and 4 or 5, are reversed. The bottom panel shows the curves redrawn after rescoring category structure (collapsing categories 1 and 2, and 4 and 5). After this merger, the three response categories for this item are well ordered and distributed, with persons with higher ability (or better quality of life) having a progressively greater probability of endorsing a higher response category.
Mentions: Mean±s.d. person location estimates were satisfactory for all domains as they were not significantly different from the corresponding centralised item location means of zero logit (Table 2). This indicated that the study sample as a whole was neither located at a better level nor located at a lower level of HRQoL than the average of the scale. Therefore, overall the scale appeared well targeted for this patient group. Graphical analysis (Figure 1), as well as formal statistical testing (Supplementary Table S2 ), did not suggest significant DIF for any item. Threshold analysis showed that threshold distances between various responses to an item varied across items. Significant anomalies for threshold patterns were observed for the WHOQOL-Bref as 10 of the 24 items had disordered thresholds (see Supplementary Table S3 and Figure 2). These results suggest that the response scales of several items were inadequate in ordering patients with distinct levels of ability. Moreover, distances between adjacent thresholds were >5 logits in 8 instances and <1.4 logits in 28 instances (see Supplementary Table S3).

Bottom Line: Item 3 (pain prevents doing work) displayed a large positive fit residual value (indicating violation of unidimensionality), resulting in poor construct validity for the physical domain.The modified scale had good construct validity for all domains, ordered thresholds for all items and good targeting of items to persons.However, when modified by Rasch analysis, the scale proved better than the original scale.

View Article: PubMed Central - PubMed

Affiliation: Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India.

ABSTRACT

Background: There is no disease-specific instrument to describe health-related quality of life (HRQoL) in Indian patients with asthma. However, an abbreviated World Health Organization Quality of Life questionnaire (WHOQOL-Bref), a generic Hindi HRQoL measure, has been developed and validated in India.

Aims: To evaluate the WHOQOL-Bref in adult patients with asthma and to test possible modifications to the instrument to improve its psychometric adequacy.

Methods: Sixty-seven patients with asthma completed the WHOQOL-Bref. Rasch analysis was used to explore the psychometric performance of the four domains (physical, psychological, social relationships and environment) of the scale. Overall fit of data to model expectations, appropriate category ordering, presence of differential item functioning, individual item fit and targeting of item difficulty to patient ability were explored for each domain. Item deletion and rescoring were applied to misfitting items to improve overall performance.

Results: The overall fit of the WHOQOL-Bref data was adequate. Item 3 (pain prevents doing work) displayed a large positive fit residual value (indicating violation of unidimensionality), resulting in poor construct validity for the physical domain. No item exhibited differential item functioning. Ten items had disordered thresholds. The WHOQOL-Bref was modified by dropping item 3 and rescoring category structures of 16 items. The modified scale had good construct validity for all domains, ordered thresholds for all items and good targeting of items to persons.

Conclusions: The WHOQOL-Bref performed inadequately in describing HRQoL in the asthma patients studied. However, when modified by Rasch analysis, the scale proved better than the original scale.

Show MeSH
Related in: MedlinePlus