The overall response rate was 53.0% (N = 1452), from 41.7% in the internal medicine/emergency clinics of both outpatients clinics (GIM/E) to 79.2% in the travel clinic. However, respondents did not differ from the eligible population as a whole to which the questionnaire was given, in age (mean 37.6 years vs 37.7). Furthermore, Swiss citizens were only slightly overrepresented compared to non-Swiss respondents (69.6/65.1). The non-response rate for each question was low, between 0.4 to 10.8% (question on concurrency).
Forty percent of the total sample was recruited from the general internal medicine/emergency clinics of both outpatient clinics (GIM/E), 31.7% from the travel clinic, 17.3% from the anonymous HIV testing clinic, 8.3% from the 5 GP clinics, and 3.4% from the dental clinic. Among these, 1431 patients had had sexual intercourse and were retained for the subsequent analysis.
We expected and found significant differences across different clinics with regard to: response rate (from 41.8% in emergencies to 79.2 in the travel clinic), mean age (from 30.7 in the HIV testing clinic to 45.7 in the five GPs clinics), nationality (from 59.4% of Swiss citizens in GIM/E clinics to 79.1 in the travel clinic), sexual behaviours (see below). Therefore the recruitment site was introduced as independent variable in the multivariate analysis.
Behaviours that posed a potential risk of exposure to STIs were reported by a high proportion of patients. Sexual intercourse with occasional partner(s) was reported by 32.4% of the patients (from 24.4% in the travel clinic to 58.2% in the HIV testing clinic, p < 0.001), and condom use with these partner(s) by 57.8% (from 50.7% in the HIV testing clinic to 67.9% in the five GP clinics, ns); With regard to age classes for comparison with the last general population survey (2000) on similar questions (see introduction), the proportion of people having had one or more occasional partners in the last 6 months in our study was 43.0% among the 17-30 years old (21% in the general population in 2007) and 33.4% among the 31-45 years old (10% in the general population in 2007); respectively 42.0% and 42.2% of them had not used condoms consistently (35% and 45% in the general population in 2000). The proportion of patients with occasional partners was substantially higher than among the male general population, and condom use with occasional partner(s) was lower among the younger patients in our sample.
Having paid for sex in the last twelve months was reported by 12.8% (from 8.0% in the GPs clinics to 15.2% in the HIV testing and the GPs clinics, p = 0.442), and condom use at last paid intercourse was reported by 94.2% (from 91.3% in the GIM/E clinic to 100% in the dental clinic, ns). Sexual concurrency was reported by 26.6% (from 19.6 in the travel clinic to 52.5% in the HIV testing clinic, p < 0.001).
Overall, 13.4% of the patients (from 8.0% in the GP's clinics to 15.2% in the HIV testing clinic, p < 0.001) were defined as patients at risk for STIs. This category included 323 patients reporting occasional partners and no paid partners, 118 patients reporting occasional partners and paid partners, and 53 patients reporting only paid partners.
90.9% of patients reported that they wished their doctor would ask them questions about their sexuality in order to receive counselling, but only 61.4% had previously had this experience and overall only 37.4% had ever received STI prevention counselling.
Patients at risk were younger than those patients who were not identified as at risk, and were more likely to have been recruited in the HIV testing clinic (Table ). There was no difference between the two groups in terms of education and employment status. Patients at risk were more likely to be of a nationality other than Swiss, to live alone, and to declare no religion. In terms of sexuality, patients at risk tended to have had an earlier sexual debut, more sex partners, more same sex intercourse experience. In addition, in the last 12 months, a higher proportion of patients at risk had had sexual concurrency and had had STI symptoms than had those patients not at risk.
Patients at risk felt less well informed about HIV/AIDS and other STIs than other patients and were less likely to have been tested for HIV. Although a higher proportion of patients at risk had been advised by a doctor on how to avoid STIs, they were not more likely to ever have discussed sexual matters with a GP as compared to those patients not at risk.
In a multivariate analysis, we found that the strongest risk factors for patients at risk were being under the age of 41 (OR 3.98), living alone (OR 3.12), and to have concurrent sexual partners (OR 5.09) (Table ).
Variables associated with patients at risk (Lausanne, 2005-2006)