The reliability of the twelve-item general health questionnaire (GHQ-12) under realistic assumptions
<p>Abstract</p> <p>Background</p> <p>The twelve-item General Health Questionnaire (GHQ-12) was developed to screen for non-specific psychiatric morbidity. It has been widely validated and found to be reliable. These validation studies have assumed that the GHQ-12 is one...
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| Format: | Article |
| Language: | English |
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BMC
2008-10-01
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| Series: | BMC Public Health |
| Online Access: | http://www.biomedcentral.com/1471-2458/8/355 |
| _version_ | 1819203131955740672 |
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| author | Hankins Matthew |
| author_facet | Hankins Matthew |
| author_sort | Hankins Matthew |
| collection | DOAJ |
| description | <p>Abstract</p> <p>Background</p> <p>The twelve-item General Health Questionnaire (GHQ-12) was developed to screen for non-specific psychiatric morbidity. It has been widely validated and found to be reliable. These validation studies have assumed that the GHQ-12 is one-dimensional and free of response bias, but recent evidence suggests that neither of these assumptions may be correct, threatening its utility as a screening instrument. Further uncertainty arises because of the multiplicity of scoring methods of the GHQ-12. This study set out to establish the best fitting model for the GHQ-12 for three scoring methods (Likert, GHQ and C-GHQ) and to calculate the degree of measurement error under these more realistic assumptions.</p> <p>Methods</p> <p>GHQ-12 data were obtained from the Health Survey for England 2004 cohort (n = 3705). Structural equation modelling was used to assess the fit of <abbrgrp><abbr bid="B1">1</abbr></abbrgrp> the one-dimensional model <abbrgrp><abbr bid="B2">2</abbr></abbrgrp> the current 'best fit' three-dimensional model and <abbrgrp><abbr bid="B3">3</abbr></abbrgrp> a one-dimensional model with response bias. Three different scoring methods were assessed for each model. The best fitting model was assessed for reliability, standard error of measurement and discrimination.</p> <p>Results</p> <p>The best fitting model was one-dimensional with response bias on the negatively phrased items, suggesting that previous GHQ-12 factor structures were artifacts of the analysis method. The reliability of this model was over-estimated by Cronbach's Alpha for all scoring methods: 0.90 (Likert method), 0.90 (GHQ method) and 0.75 (C-GHQ). More realistic estimates of reliability were 0.73, 0.87 and 0.53 (C-GHQ), respectively. Discrimination (Delta) also varied according to scoring method: 0.94 (Likert method), 0.63 (GHQ method) and 0.97 (C-GHQ method).</p> <p>Conclusion</p> <p>Conventional psychometric assessments using factor analysis and reliability estimates have obscured substantial measurement error in the GHQ-12 due to response bias on the negative items, which limits its utility as a screening instrument for psychiatric morbidity.</p> |
| first_indexed | 2024-12-23T04:15:03Z |
| format | Article |
| id | doaj.art-dc0dc057b7124a41ae1c515e30389f8e |
| institution | Directory Open Access Journal |
| issn | 1471-2458 |
| language | English |
| last_indexed | 2024-12-23T04:15:03Z |
| publishDate | 2008-10-01 |
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| spelling | doaj.art-dc0dc057b7124a41ae1c515e30389f8e2022-12-21T18:00:23ZengBMCBMC Public Health1471-24582008-10-018135510.1186/1471-2458-8-355The reliability of the twelve-item general health questionnaire (GHQ-12) under realistic assumptionsHankins Matthew<p>Abstract</p> <p>Background</p> <p>The twelve-item General Health Questionnaire (GHQ-12) was developed to screen for non-specific psychiatric morbidity. It has been widely validated and found to be reliable. These validation studies have assumed that the GHQ-12 is one-dimensional and free of response bias, but recent evidence suggests that neither of these assumptions may be correct, threatening its utility as a screening instrument. Further uncertainty arises because of the multiplicity of scoring methods of the GHQ-12. This study set out to establish the best fitting model for the GHQ-12 for three scoring methods (Likert, GHQ and C-GHQ) and to calculate the degree of measurement error under these more realistic assumptions.</p> <p>Methods</p> <p>GHQ-12 data were obtained from the Health Survey for England 2004 cohort (n = 3705). Structural equation modelling was used to assess the fit of <abbrgrp><abbr bid="B1">1</abbr></abbrgrp> the one-dimensional model <abbrgrp><abbr bid="B2">2</abbr></abbrgrp> the current 'best fit' three-dimensional model and <abbrgrp><abbr bid="B3">3</abbr></abbrgrp> a one-dimensional model with response bias. Three different scoring methods were assessed for each model. The best fitting model was assessed for reliability, standard error of measurement and discrimination.</p> <p>Results</p> <p>The best fitting model was one-dimensional with response bias on the negatively phrased items, suggesting that previous GHQ-12 factor structures were artifacts of the analysis method. The reliability of this model was over-estimated by Cronbach's Alpha for all scoring methods: 0.90 (Likert method), 0.90 (GHQ method) and 0.75 (C-GHQ). More realistic estimates of reliability were 0.73, 0.87 and 0.53 (C-GHQ), respectively. Discrimination (Delta) also varied according to scoring method: 0.94 (Likert method), 0.63 (GHQ method) and 0.97 (C-GHQ method).</p> <p>Conclusion</p> <p>Conventional psychometric assessments using factor analysis and reliability estimates have obscured substantial measurement error in the GHQ-12 due to response bias on the negative items, which limits its utility as a screening instrument for psychiatric morbidity.</p>http://www.biomedcentral.com/1471-2458/8/355 |
| spellingShingle | Hankins Matthew The reliability of the twelve-item general health questionnaire (GHQ-12) under realistic assumptions BMC Public Health |
| title | The reliability of the twelve-item general health questionnaire (GHQ-12) under realistic assumptions |
| title_full | The reliability of the twelve-item general health questionnaire (GHQ-12) under realistic assumptions |
| title_fullStr | The reliability of the twelve-item general health questionnaire (GHQ-12) under realistic assumptions |
| title_full_unstemmed | The reliability of the twelve-item general health questionnaire (GHQ-12) under realistic assumptions |
| title_short | The reliability of the twelve-item general health questionnaire (GHQ-12) under realistic assumptions |
| title_sort | reliability of the twelve item general health questionnaire ghq 12 under realistic assumptions |
| url | http://www.biomedcentral.com/1471-2458/8/355 |
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