BMC Public Health 2007, 7:349 http://www.biomedcentral.com/1471-2458/7/349 by a public endorsement for CVCT by the INA or another community leader. INA follow-up Weekly follow-up meetings were held to discuss chal- lenges INAs encountered during their work. Completed "invitation receipts" were collected. INAs were encour- aged to begin slowly (10 invitations/week) and build up to a manageable volume. The maximum number of invi- tations distributed overall was determined by the capacity of the testing centre. A process oriented method of pay- ment was employed. INAs received a small incentive pay- ment for each invitation delivered, a larger payment for any couples who attended a CVCT session and transporta- tion costs to facilitate attendance at the weekly meetings. CVCT procedures CVCT procedures have been previously described [4]. Briefly, each morning 10–25 couples participated in a group discussion led by a counsellor. This was followed by joint confidential pre-test counselling sessions, informed consent procedures if HIV testing was desired, phlebotomy, and lunch while rapid HIV testing was per- formed. These services were provided free of charge and included a reimbursement of transportation expenses and child care. Results and joint post-test counselling were provided in the afternoons. All blood tubes and result forms were coded with a couple testing ID number. CVCT clients were a mixture of INA-invited and 'walk-in' cou- ples; the data presented here are limited to couples invited by INAs. Invitations were collected from INA-invited cou- ples at the time of pre-test counselling, and the invitation number was linked to the couple testing ID number for the purposes of this analysis. Statistical Analysis Data were entered in Access databases and analyzed with the SAS statistical package (version 9.0; Statistical Analysis Software, North Carolina, USA). Two outcomes are examined to measure the 'success' of INA invitations. First, we examined predictors of the number of invitations distributed per INA using standard linear regression models. Second, we tracked which cou- ples came for testing and examined the predictors of a 'successful' invitation. Because invitations are nested or clustered within individual INAs and therefore not inde- pendent observations, a hierarchical or nested random- effects model was used to estimate error variability at both the INA and couple levels simultaneously. We used the Hierarchical Linear Modelling (HLM) analysis system developed by Raudenbush and colleagues [28] to accom- plish this objective. Each invitation was coded as success- ful or unsuccessful based on whether the couple later attended the CVCT centre. This binary outcome variable was analyzed as a function of invitation-level and INA- level predictors. The logit link function was applied to this binary outcome variable, making the HLM analysis anal- ogous to a hierarchical or clustered extension of standard logistic regression analysis. The iterative, penalized quasi- likelihood (PQL) estimation method was used, and the unit-specific estimates, odds ratios, confidence intervals, and t-tests were used to evaluate each predictor. Variables to be considered in the multivariate analysis were selected based on the results of univariate analysis, using p < .05 as the criteria. Results INA characteristics In Kigali, 28 INAs included 10 men and 18 women, with 5 religious group affiliates, 8 health-care providers, 5 NGO/CBO members, and 10 private sector representa- tives. In Lusaka, 33 INAs included 20 men and 13 women, of whom 10 were affiliated with religious groups, 8 were health-care providers, 6 worked with NGO/CBO, and 9 were from the private sector. The mean age of INAs was 40 years in both cities (range 20–65) and they lived in the catchment area of the CVCT centres. Forty-one of the 61 INAs (67%) received HIV counselling and testing prior to or during the training period, of whom 26 were tested with their spouses. Invitations to attend CVCT Invitations were distributed to 9,900 couples (2,680 in Rwanda, 7,220 in Zambia) in a 4 month period. The aver- age ages of invited men and women in each country were similar (Rwanda: Men = 35.6 years, Women = 29.6 years; Zambia: Men = 34.5 years, Women = 28.1 years). Couples had been married or cohabiting for a mean of 8.0 years (Rwanda = 7.8 years, Zambia = 8.0 years), and had an average of 2.5 children (Rwanda = 2.5, Zambia = 2.4). Table 1 presents the contextual characteristics of CVCT invitations given by INAs, stratified by category and city. Invitations in Rwanda and Zambia were similar in that 56% were given to someone known to the INA, including professional or social contacts, friends, or family mem- bers. Rwandan INAs were more likely than Zambian counterparts to invite both members of the couple together (33% vs. 25%) rather than the man or woman alone. In both cities, 60% of invitations were delivered at the client's home, with the remainder given at the INA home, workplace or clinic, or in the community (includ- ing church, market, social gathering, or other). Zambian INAs were more likely to deliver invitations accompanied by their spouse (12% of invitations) or another INA (8%), while Rwandan INAs tended to work alone (95% of invi- tations). Invitations in Rwanda had more often been pre- ceded by a public endorsement of CVCT than those in Zambia (11% vs. 6%). Page 3 of 10 (page number not for citation purposes)