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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

Graphical exploration of differential item functioning for item 18 (capacity for work) of the abbreviated World Health Organization Quality of Life. The dashed line corresponds to the item characteristic curve representing the expected probability of item endorsement as a function of person ability. Superimposed plots represent the observed responses by patients of either gender (left panel), different age groups (middle panel) and different levels of asthma control (right panel). For each analysis, patients were divided into three approximately equal groups according to their health-related quality of life. Individual plots for each analysis lie close to each other, with no obvious dissimilarities. Group differences were also statistically non-significant on formal analysis of variance testing, suggesting that item response functions were largely invariant across categories.
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fig1: Graphical exploration of differential item functioning for item 18 (capacity for work) of the abbreviated World Health Organization Quality of Life. The dashed line corresponds to the item characteristic curve representing the expected probability of item endorsement as a function of person ability. Superimposed plots represent the observed responses by patients of either gender (left panel), different age groups (middle panel) and different levels of asthma control (right panel). For each analysis, patients were divided into three approximately equal groups according to their health-related quality of life. Individual plots for each analysis lie close to each other, with no obvious dissimilarities. Group differences were also statistically non-significant on formal analysis of variance testing, suggesting that item response functions were largely invariant across categories.

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)

Graphical exploration of differential item functioning for item 18 (capacity for work) of the abbreviated World Health Organization Quality of Life. The dashed line corresponds to the item characteristic curve representing the expected probability of item endorsement as a function of person ability. Superimposed plots represent the observed responses by patients of either gender (left panel), different age groups (middle panel) and different levels of asthma control (right panel). For each analysis, patients were divided into three approximately equal groups according to their health-related quality of life. Individual plots for each analysis lie close to each other, with no obvious dissimilarities. Group differences were also statistically non-significant on formal analysis of variance testing, suggesting that item response functions were largely invariant across categories.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig1: Graphical exploration of differential item functioning for item 18 (capacity for work) of the abbreviated World Health Organization Quality of Life. The dashed line corresponds to the item characteristic curve representing the expected probability of item endorsement as a function of person ability. Superimposed plots represent the observed responses by patients of either gender (left panel), different age groups (middle panel) and different levels of asthma control (right panel). For each analysis, patients were divided into three approximately equal groups according to their health-related quality of life. Individual plots for each analysis lie close to each other, with no obvious dissimilarities. Group differences were also statistically non-significant on formal analysis of variance testing, suggesting that item response functions were largely invariant across categories.
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