Study setting
Trinidad and Tobago, a twin-island republic located in the southern Caribbean, with a population of 1.3 million persons. The Ministry of Health (MoH), through five autonomous Regional Health Authorities (RHAs), deliver free public health care services.
To address STI transmission, several interventions were developed and implemented. These include the delivery of targeted STI education sessions in all schools throughout Trinidad and Tobago, free HIV/AIDS and STI screening at the Queen’s Park Counseling Centre and Clinic (QPCC&C), health centres and district health facilities, community outreach initiatives (i.e. mobile clinics and health education sessions) and condom distribution at primary healthcare facilities. Notably, the QPCC&C, established in 1944, is a public specialist clinic for the testing, treatment, and management of STIs. It is a walk-in clinic operating from two locations in Trinidad: Port-of-Spain (North) and San Fernando (South).
Study design and population
Between May and June 2024, a cross-sectional study was conducted among adults aged 18 years or older attending both QPCC&C-STI clinic sites.
Sampling technique and sample size
Due to the logistical constraints, operational nature of the clinic and the lack of a sampling frame, convenience sampling was employed. A sample size of 260 individuals was calculated using an estimated 16.2% prevalence for STI based on Ray et al. 2006 [27], significance level (α) of 0.05, margin of error of 5% and a 20% non-response rate.
While no subgroup analyses, between sex and STI, were originally planned, a post-hoc power analysis, using G*Power version 3.1.9.7 [33], showed that the final sample size of 250 provided moderate power (77%) to detect meaningful differences, such as an odds ratio of 2.
Data collection instrument and procedure
The clinic nurses were briefed on the study’s purpose and invited patients to participate. A total of 310 patients were approached, of whom 250 expressed an interest. The researchers enrolled these individuals after completing the informed consent process. All interviews were conducted in a private room to maintain confidentiality.
Interviewer-administered questionnaires were used, by trained interviewers/researchers, to collect data over a 25–35-minute period. The questionnaire comprised 26 items, adapted from Edwards et al. 2019 [32]. All data were recorded using the REDCap© (Research Electronic Data Capture), an electronic data capture tool, hosted by The UWI Cave Hill Campus.
Study variables and measurements
Independent variables
Socio-demographic characteristics
Data were collected on participant’s gender, date of birth, ethnicity, marital status, education, employment status, and household income. Participants reported their gender identity as male, female, non-binary or transgender. Ethnic groups were reported as Afro- or Indo-Trinidadian, mixed or other ethnicities. For this study, marital status was categorized as single, married, common law relationship, separated, divorced, or widowed. Socioeconomic status indicators such as highest level of educational attainment, employment status, and household income were collected. Education was categorized as: none, primary, secondary, vocational training and tertiary. Participants’ employment status was measured as employed, self-employed, unemployed and student. While monthly household income was categorized as follows: 588 United States Dollar (USD), 589–882 USD, 883–1176 USD and ≥ 1177 USD.
Sexual behaviours
Participants were asked about their sexual activity (Yes/No) within the past 12 months and their sexual orientation. Those who were sexually active were asked about: information on condom use (condom use during last sexual encounter and frequency of condom use), number of sexual partners (within the previous 12 months) and awareness of partner’s HIV status. Sexual orientation examined the sexual preferences of the participants: queer, hetero-, homo-, demi-, pan-, bi- or asexual. We also examined how often participants used condoms during sex (Never/Sometimes/Always) and if they used a condom during their last sexual encounter (Yes/No). Data on the number of sexual partners within the past 12 months and awareness of their sexual partners’ HIV status (Yes/No) were recorded.
Substance use (Drug Use and Alcohol Consumption)
Data on illicit or decriminalized drugs were collected as Yes/No responses to use of marijuana/weed, cocaine – crack/powder, ecstasy, heroin and methamphetamine. For alcohol consumption, the categories of use were: I do not drink alcohol, social drinker, 1–2 times/week, 3–4 times/week, and ≥ 5 times/week.
Dependent variable
Self-reported STI (gonorrhea, syphilis, herpes, chlamydia, HIV/AIDS, trichomoniasis, human papillomavirus (HPV), and hepatitis C) status within the last 12 months was also recorded. Case definitions for each STI were included in the data collection instrument [34,35,36,37,38,39,40,41].
Manipulated variables
The following variables were manipulated for data analysis:
-
Age was calculated using participants’ date of birth and the following age-group categories were generated: 18–24 years, 25–31 years, 32–38 years, 39–45 years and ≥ 46 years.
-
Education was dichotomized to represent participants with secondary or lower and vocational or higher qualifications.
-
Marital status categories were recoded to single, married/in a common law relationship or separated/widowed/divorced.
-
Sexual orientation was dichotomized to represent heterosexual and non-heterosexual persons.
-
The number of sexual partners reported within the last 12 months was dichotomized: 1 and ≥ 2 sexual partners.
-
Alcohol consumption categories were recoded to I do not drink alcohol, social drinkers, ≤ 2 times per week, and ≥ 3 times per week.
Statistical analysis
Descriptive statistics such as frequencies and percentages were generated for participants’ socio-demographic characteristics, sexual orientation, practices and activity, condom use, substance use and self-reported STI prevalence within the last 12 months. Overall self-reported STI prevalence was generated using participants’ STI status (gonorrhea, syphilis, herpes, chlamydia, HIV/AIDS, trichomoniasis, HPV, and hepatitis C). Pearson’s Chi-Squared test was used to examine associations between gender and demographic variables, sexual orientation, sexual behaviours (lifetime and last condom use, number of sexual partners, and partner’s HIV status), substance use (alcohol and drugs) and self-reported STI prevalence reported within the past year. Bivariate logistic regression was conducted to examine potential associations between self-reported STI prevalence and selected study variables, using crude odds ratios (OR) with 95% confidence intervals and p-values (variables with p-values less than 0.05 were considered significant). Pairwise deletion was used to handle missing data. All statistical analyses were conducted using STATA (version 15).