BMC Public Health 2004, 4 http://www.biomedcentral.com/1471-2458/4/22 prevalence of food insecurity obtained using self-reported measures must be interpreted with caution. Associations obtained within populations are likely to be less sensitive to such problems, but even here they cannot always be ignored [28]. Our data suggested that the pattern of responses was generally similar in each ethnic group but there was evidence that two of the items might have slightly different relative severities in different groups. Murray et al [29] observe that 'a critical requirement is an improved understanding of the determinants of differ- ences between self-reported and observed measures of performance or capacity in selected domains in health' (page 991). This observation also applies in the assess- ment of food insecurity. Competing interests None declared. Contributions DM had the original idea for the survey and contributed to the design and implementation of the study, BR con- tributed to the design of the study and oversaw the collec- tion of data, MG designed the questionnaire and measurement forms, analysed the data and drafted the paper. All authors read and approved the first version of the paper, MG and BR approved the final version of the paper. MG is guarantor. Abbreviations ICC, intraclass correlation coefficient SII, slope index of inequality UN, United Nations US, United States. Acknowledgements tion in working on the survey. References The authors thank the Chief Medical Officer of Trinidad and Tobago for permission to report this work. We also thank the staff of the Central Sta- tistical Office for help in drawing the sample and for advice on conducting the survey and the staff of the Nutrition Division for their skill and dedica- 1. 2. 3. 4. 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