Ziraba et al. BMC Public Health 2011, 11:663 http://www.biomedcentral.com/1471-2458/11/663 serology on DBS was carried out using Determine® HIV- 1/HIV-2 (Abbott) and Uni-Gold™ rapid test kits. Data analysis Descriptive and multivariate analyses were carried out using Stata statistical software version 10. The depen- dent variable was categorised as trichotomous thus: Never tested; Client-Initiated Testing and Counselling (CITC) and Provider-Initiated Testing and Counselling- (PITC). Tests carried out for purposes of emigration, employment or travel were very few (3.7%) and for ana- lytical purposes these were grouped together with provi- der-initiated testing and counselling. Individuals who had never tested for HIV were further asked whether they would like to be tested. Responses from those who indicated that they want to be tested were used to mea- sure the unmet need for testing and counselling. In this regard, unmet need for HIV testing in this paper is defined as the proportion of respondents who have never had testing and counselling for HIV, but would like to be tested. Multinomial logistic regression models were fitted to identify determinants of HIV testing status. We ran several bivariate models and identified variables that were signifi- cantly associated with the outcome at 10% level of signifi- cance and included them in the multinomial regression analysis. In addition, we also included variables that have been reported in the literature to be associated with the outcome variable even if they were not significant at bivariate analysis. Variables that were used in the final model included; stigma, mobility, HIV/AIDS-related knowledge, HIV status, opinion on testing, knowledge of a facility that offers HIV/AIDS-related services, risky sexual behaviour, age at sexual debut, education level, ethnicity, marital status, wealth, slum of residence, age and sex. The estimates in the final model for each of the variables are adjusted, controlling for all the other variables. Stigma was computed as a score from a set of four questions, three on avoidance and one on secrecy about HIV thus: Would you buy fresh vegetables from a vendor who has the virus that causes AIDS? If a female teacher has the virus that causes AIDS, should she be allowed to continue teaching in school? If a relative of yours became sick with the virus that causes AIDS, would you be willing to care for her or him in your own home? If a member of your family got infected with the virus that causes AIDS, would you want it to remain a secret? After taking careful consideration of the direction of the questions and the responses given, we found that Cronbach’s alpha was low -less than 50%. Also, because of the limited dimensional- ity of the data (4 questions) we felt that use of principal component analysis (PCA) would not be a good idea. As a last resort, we measured stigma as a count score based on the four questions asked. Page 3 of 10 The mobility index was taken to be a weighted count of movement episodes of individuals within or outside the demographic surveillance area per unit time. An individual was considered to be highly mobile if they had at least one or more episodes of internal change of residence per year or at least one outmigration and return episode to the surveillance area in two years. HIV/AIDS-related knowl- edge index was computed from a set of questions about knowledge of HIV transmission; prevention and miscon- ceptions similar to those used in Demographic and Health Surveys (DHS) [8] using PCA. Household wealth index was computed using PCA and the items used for the com- putation included ownership of television, radio, bicycle and amenities such as water, toilet, and house building materials. Risky sexual behaviour was measured using one question on multiple sexual partnerships. An individual was classified as having had high risk sexual activity if they had two or more sexual partners in the last twelve months before the survey. Respondent’s opinion about HIV testing was based on a single question “Do you think it is impor- tant for people to know if they have the virus that causes AIDS”. We carried out a Wald’s test using a user written pro- gram implemented in Stata (spost) using the command mlogtest to determine whether any of the three categories of the outcome variable could be combined with another. The hypothesis being tested was “all coefficients except intercepts associated with a given pair of outcomes are zero (i.e. categories can be collapsed)” [30]. Each pair of outcomes was significantly different: Never tested Vs CITC-chi square = 136, df = 35, p value < 0.001; Never tested Vs PITC-chi square = 239, df = 36, p value < 0.001; and CITC Vs PITC-chi square = 113, df = 36, p value < 0.001, indicating that the categories could not possibly be collapsed hence the appropriateness of multinomial logis- tic model. Results Approximately 31% of participants who were interviewed had ever been tested for HIV in the past through CITC, 22% through PITC while the rest had never been tested (see Table 1). The highest proportions of individuals who had CITC were recorded among the age categories of 20-24, 25-29 and 30-34 years. More females (33%) had ever been tested through CITC compared to 29% among males. The divorced/separated/widowed also had higher proportions of individuals who had had CITC (43%) com- pared to 31% among those who were currently married. Approximately 57% of individuals with higher education had been tested through CITC compared to only 29% among those with no formal education. Among all identi- fiable groups, individuals between the age of 20 to 35 years, females, the married and those with no formal edu- cation tended to have been tested through PITC compared