Substance Use, Risky Behaviours and HIV Testing Among MSM
Substance Use, Risky Behaviours and HIV Testing Among MSM
Detailed sampling method and measurement procedures of the study have been described elsewhere. Briefly, using the method of Kelsey and colleagues, we estimated an adequate sample size to be 341. This calculation took into consideration the estimated ratio of the number of non-injecting to injecting MSM (13), the prevalence level of HIV in non-injecting MSM (7%) and an OR (4.0) to ensure sufficient statistical power. By including an estimated 10% refusal rate for blood collection and damaged specimens, this resulted in an effective sampling size of 380. Eligible study respondents were male persons, at least 15 years of age, having had anal and/or oral sex with another man within 12 months prior to the survey, and who had been living in study locations for at least 1 month. A total of 381 MSM respondents in two (Long Xuyen and Chau Doc) of the 11 districts in An Giang province were recruited in this community-based cross-sectional study between August and December 2009 by using a two-stage cluster sampling. Face-to-face interviews were held with the eligible respondents to elicit study information. After the interviews, blood and urine samples were collected for testing for HIV, syphilis, Chlamydia trachomatis and Neisseria gonorrhoea. The study was approved by Institutional Review Boards of the Pasteur Institute, Ho Chi Minh City, Vietnam (reference number: 316/QD-PAS), and the University of New South Wales Australia, Sydney, Australia (reference number: HC14161).
The study outcome variables were injecting drug use, daily alcohol use, having multiple UAI partners (defined as having UAI with at least two male sexual partners) in the previous month and having been tested for HIV in the previous 12 months. Prevalence ratios were used to measure the magnitude of the association between each of the four outcome variables with demographic, sexual and drug-using characteristics identified in multivariate regression models with backward elimination. All statistical analyses were performed using Stata 12 (Stata Corporation, College Station, Texas, USA).
Methods
Detailed sampling method and measurement procedures of the study have been described elsewhere. Briefly, using the method of Kelsey and colleagues, we estimated an adequate sample size to be 341. This calculation took into consideration the estimated ratio of the number of non-injecting to injecting MSM (13), the prevalence level of HIV in non-injecting MSM (7%) and an OR (4.0) to ensure sufficient statistical power. By including an estimated 10% refusal rate for blood collection and damaged specimens, this resulted in an effective sampling size of 380. Eligible study respondents were male persons, at least 15 years of age, having had anal and/or oral sex with another man within 12 months prior to the survey, and who had been living in study locations for at least 1 month. A total of 381 MSM respondents in two (Long Xuyen and Chau Doc) of the 11 districts in An Giang province were recruited in this community-based cross-sectional study between August and December 2009 by using a two-stage cluster sampling. Face-to-face interviews were held with the eligible respondents to elicit study information. After the interviews, blood and urine samples were collected for testing for HIV, syphilis, Chlamydia trachomatis and Neisseria gonorrhoea. The study was approved by Institutional Review Boards of the Pasteur Institute, Ho Chi Minh City, Vietnam (reference number: 316/QD-PAS), and the University of New South Wales Australia, Sydney, Australia (reference number: HC14161).
The study outcome variables were injecting drug use, daily alcohol use, having multiple UAI partners (defined as having UAI with at least two male sexual partners) in the previous month and having been tested for HIV in the previous 12 months. Prevalence ratios were used to measure the magnitude of the association between each of the four outcome variables with demographic, sexual and drug-using characteristics identified in multivariate regression models with backward elimination. All statistical analyses were performed using Stata 12 (Stata Corporation, College Station, Texas, USA).
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