BMC Public Health 2009, 9:100 http://www.biomedcentral.com/1471-2458/9/100 pared with the Dutch population, respondents were younger, more often female, and more highly educated [8]. Next, a non-respondent analysis revealed that non- respondents were younger and less highly educated than respondents. As it can be assumed that the use of self-tests is higher among Internet users than among non-Internet users [10], we assume that the use of self-tests among our Internet sample is higher than among the general Dutch population. Furthermore, some respondents might not have noticed or understood that the survey was limited to diagnostic self-tests, and might also have reported moni- toring tests. Although the extent of this bias remains unclear, we expect it to be limited, for two reasons. First, we provided instructions in the questionnaire on the def- inition of diagnostic self-test (see additional file 1: Ques- tionnaire on Self-tests). Second, a secondary analysis of a subgroup of self-testers in our study revealed that their response to the (open-ended) question about their main reason for self-testing gave little indication of monitoring tests being reported. Another limitation of our study was that it had a cross-sectional design, so no conclusions about causality can be drawn. Finally, our results are based on self-testers in general, and we assessed only a limited number of possible correlates. It is obvious that the characteristics of self-testers and their reasons for test- ing, as well as the pros and cons of self-tests, are likely to vary with the type of test. In the Netherlands there is currently a debate about the desirability of self-testing [11]. Whatever the outcome of this debate, self-testing exists and is likely to increase. It is therefore essential to develop appropriate information for consumers, as well as for health care providers and policy- makers, about the pros and cons of self-testing and of spe- cific self-tests. Conclusion In conclusion, despite the limitations of the study, self- testing proved to be relatively prevalent in the Nether- lands and is a phenomenon that cannot be ignored. On the other hand, self-tests and self-testers cannot be seen as homogeneous groups and more test-specific research is needed. In an ongoing study we are investigating trends in the use of self-tests, psychosocial correlates of their use, consumers' information needs and consumers' follow-up behaviour, in general as well as for specific self-tests. Competing interests The authors declare that they have no competing interests. Authors' contributions GR and TvdW were involved in all aspects of the study and drafted the manuscript. PP was involved in the develop- ment of the questionnaire and the data analyses. RN was involved in the development of the questionnaire. GD and FB had a consultative role during all aspects of the study. All of the authors contributed substantially to the production of the manuscript and have read and approved the final version. Additional material Additional file 1 Self-tests: September 2006. The file contains a copy of the questionnaire (translated into English) that was sent to the entire panel of 12,529 per- sons aged 12 years and over. Click here for file [http://www.biomedcentral.com/content/supplementary/1471- 2458-9-100-S1.doc] Acknowledgements This study was financially supported by the Dutch Health Care Insurance Board (CVZ). References 1. 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Ned Tijdschr Geneeskd 2007, 151(16):901-904. Pre-publication history The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1471-2458/9/100/pre pub Page 6 of 6 (page number not for citation purposes)