BMC Public Health Research article Reliability and validity of a short form household food security scale in a Caribbean community Martin C Gulliford*1, Deepak Mahabir2 and Brian Rocke2 BioMed Central Open Access Address: 1Department of Public Health Sciences King's College London and 2Nutrition and Metabolism Division Ministry of Health Laventille Trinidad and Tobago Email: Martin C Gulliford* - martin.gulliford@kcl.ac.uk; Deepak Mahabir - martin.gulliford@kcl.ac.uk; Brian Rocke - martin.gulliford@kcl.ac.uk * Corresponding author Published: 16 June 2004 BMC Public Health 2004, 4:22 This article is available from: http://www.biomedcentral.com/1471-2458/4/22 Received: 23 October 2003 Accepted: 16 June 2004 © 2004 Gulliford et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL. food securityfood insecurityreliabilityvalidityquestionnairesWest IndiesTrinidad and Tobago Abstract Background: We evaluated the reliability and validity of the short form household food security scale in a different setting from the one in which it was developed. Methods: The scale was interview administered to 531 subjects from 286 households in north central Trinidad in Trinidad and Tobago, West Indies. We evaluated the six items by fitting item response theory models to estimate item thresholds, estimating agreement among respondents in the same households and estimating the slope index of income-related inequality (SII) after adjusting for age, sex and ethnicity. Results: Item-score correlations ranged from 0.52 to 0.79 and Cronbach's alpha was 0.87. Item responses gave within-household correlation coefficients ranging from 0.70 to 0.78. Estimated item thresholds (standard errors) from the Rasch model ranged from -2.027 (0.063) for the 'balanced meal' item to 2.251 (0.116) for the 'hungry' item. The 'balanced meal' item had the lowest threshold in each ethnic group even though there was evidence of differential functioning for this item by ethnicity. Relative thresholds of other items were generally consistent with US data. Estimation of the SII, comparing those at the bottom with those at the top of the income scale, gave relative odds for an affirmative response of 3.77 (95% confidence interval 1.40 to 10.2) for the lowest severity item, and 20.8 (2.67 to 162.5) for highest severity item. Food insecurity was associated with reduced consumption of green vegetables after additionally adjusting for income and education (0.52, 0.28 to 0.96). Conclusions: The household food security scale gives reliable and valid responses in this setting. Differing relative item thresholds compared with US data do not require alteration to the cut- points for classification of 'food insecurity without hunger' or 'food insecurity with hunger'. The data provide further evidence that re-evaluation of the 'balanced meal' item is required. Background Food insecurity has been defined as the 'limited or uncer- tain availability of nutritionally adequate and safe foods, or limited or uncertain ability to acquire food in socially Page 1 of 9 (page number not for citation purposes)