Data source
The present cross-sectional study is part of a series of reiterating biobehavioral surveillance surveys (BBSSs) on HBV and HCV among Iranian prisoners that were carried out in 2015 and 2016. The methodology of BBSSs was the same in both rounds of the study and it is comprehensively presented in published BBSSs (6, 17), however, a summary is provided below. The study population included all Iranian prisoners who were in prison at the time of the study. Using multi-stage random sampling method, the subjects were selected. First, all the 31 provinces of Iran were categorized into three groups, namely the north, center, and south groups. Then, three provinces from each category, and 2–4 prisons from each province were randomly selected (9 provinces and 26 prisons in 2015 and 10 provinces and 29 prisons in 2016 were included in the study). Considering the average population of incarcerated people in each province and prison per year, the required number of samples in each prison was determined through probability-proportional-to-size sampling method. Finally using systematic random sampling, eligible prisoners (Iranian, age >18 years, and with a history of prison term of at least one month at the time of the study) were recruited from the roster of all inmates in the prison; after obtaining a written informed consent, the selected people were enrolled into the study. Accordingly, over the two rounds, 12,800 Iranian prisoners including 6200 persons in 2015 and 6600 persons in 2016 that accounted for 0.06 and 0.10 of the total population of prisoners in the selected cities were recruited. Of the 12800 selected subjects, 11988 persons (5507 persons in 2015 and 6481 persons in 2016) participated in the surveys. Of these participants (11988), 1387 prisoners had a history of injecting drug use in their lifetime, all of whom formed our study population.
Data collection tool
Demographic and behavioral data
In both rounds, a questionnaire-based interview was performed to collect data on demographics and behavioral status of the participants. The questionnaires, included seven sections (collecting data on demographic variables, criminal records, history of sexually transmitted diseases (STD), knowledge about HBV and HCV, and history of high-risk behaviors including drug abuse, tattooing and piercing). All demographic and behavioral data were collected via self-report. The variables were defined as below:
Illiteracy: Inability to read and write.
Primary education: This category included people who just attended a primary school. In Iran, primary school lasts 5 years. In other words, this category included people who had successfully passed at minimum of 1 and a maximum of 5 years of education in a primary school.
Junior high school: This category included people who attended a junior high school and no more. In Iran, junior high school lasts from 1 to 3 years. In other words, this category included people who had successfully passed in minimum of 1 and a maximum of 3 years in a junior high school.
Diploma: This category included people who had completed primary, junior and senior high school successfully. In other words, this category included people who had successfully completed at least 5 years of primary school, 3 years of junior high school, and 3 years of senior high school.
University education: It included people who had successfully finished high school education and were graduated in an academic filed in a university.
History of imprisonment: This category included people with a history of incarceration other than the present term of incarceration.
Number of incarcerations: Frequency of records of imprisonment other than the present term of incarceration; it was calculated for those with a previous history of imprisonment.
Prison term in the lifetime: Sum of the years of imprisonment; it was calculated for those with a history of imprisonment.
History of tattooing in the lifetime: History of injecting ink into the skin in the lifetime in every place.
History of tattooing in prison: History of injecting ink into the skin in prison; it was calculated for those with a history of tattooing in the lifetime.
History of piercing in the lifetime: History of making a hole in ear, lip, mouth, navel, and breast by a needle and cupping in the lifetime in every place.
History of piercing in prison: History of making a hole in ear, lip, mouth, navel, and breast by a needle and cupping at prison; it was calculated for those with a history of piercing in the lifetime.
History of extramarital sex in the lifetime: Engagement of a married person in a sexual affair with someone other than his/her legal spouse.
Number of sexual partners in the lifetime: Number of people, other than a legal spouse, that a married person had sexual activity with, either heterosexual or homosexual. It was calculated for those with a history of extramarital sex in the lifetime
History of STD: Symptomatic self-reported history of wounds or abnormal secretion from genital area (abnormal in terms of amount, color, and odor), and STDs diagnosed by a physician.
Serologic data
Blood samples were collected and sent for serological testing to verify the exposure to HBV and HCV. Dried blood spot samples were collected from individuals who consented to participate in the study; the collected samples were stored under a standard condition. The presence of HBsAg and HCV antibodies were evaluated through assessing optical density (od) and cut-off points in ELISA (Enzyme-Linked Immunosorbent Assay) using Dia Pro kits (Diagnostic Bioprobes Srl, Italy). The validity of the results was verified using repeat testing for both positive and negative cases. All the tests on blood samples were carried out in the Pasteur Institute of Iran.
The questioning team in each prison consisted of two trained individuals: a) an interviewer selected among people working in health and treatment departments of prisons, b) a blood sampler selected among the staff working in a university of medical sciences.
Statistical analysis
Data were analyzed using the survey package in Stata/SE software, Version 14.0. Following the survey design, weighting, clustering, and stratification were performed on the data collected from a total of 12800 samples. Weights of the samples were determined using poststratification method, and postweight instrument. The frequency distribution of poststrata was determined through assessing people’s willingness to participate in the study. Finally the data required for this study was analyzed using descriptive statistics (frequency and mean) and analytical statistics (chi-square test, univariate and multivariate logistic regression). Since there were a large number of variables, only the variables with a P < 0.2 in the chi-square test were selected for multivariate analysis.