Data source
The present cross-sectional study is part of a series of reiterating biobehavioral surveillance surveys (BBSSs) of HBV and HCV among Iranian prisoners that were carried out in 2015 and 2016. The methodology of BBSSs was the same in both periods and is presented in comprehensively published BBSSs (12, 17), however, a summary is provided below. The statistical population included all Iranian prisoners who were in prison at the time of the study. The prisoners were sampled via multi-stage random sampling method. 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 selected randomly (9 provinces and 26 prisons in 2015 and 10 provinces and 29 prisons in 2016 were included in the study). Next, the required number of samples from each prison was determined using probability-proportional-to-size sampling method based on the average annual population of incarcerated people in each province and prison. 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 and after obtaining a written informed consent were enrolled into the study. Accordingly, over the two rounds, 12,800 Iranian prisoners including 6200 in 2015 and 6600 in 2016 that accounted for 0.06 and 0.10 of the total prisoners in the selected cities were recruited. Of the 12800 selected subjects, 11988 (5507 in 2015 and 6481 in 2016) participated in the surveys. Of these participants (11988), 1387 prisoners had a history of injecting drug use in the lifetime and formed our study population.
Data collection tool
Demographic and behavioral data
In both rounds, a questionnaire-based interview was used for collecting data on demographics and behavioral status of the participants. The questionnaires, included seven sections (demographic data, criminal records, history of sexually transmitted diseases (STD), knowledge about HBV and HCV, and three other sections about high-risk behaviors including drug abuse, tattooing and piercing). All demographic and behavioral data was collected via self-report. The variables were defined as below:
Illiteracy: Inability to read and write.
Primary school, Junior high school, or Diploma: Having the last degree of education at every educational level.
University education: A certificate of general and specialized knowledge and skills acquired from a university or other formal educational centers.
History of imprisonment: At least a history of imprisonment 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 whole 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 whole 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 activity 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, whether 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 secretion from the genital area that are abnormal in terms of amount, color, and odor and STDs diagnosed by a physician.
Serologic data
Blood samples were collected for serological testing to examine HBV and HCV exposure. Dried blood spot samples were collected from individuals who consented to participate in the study and stored under a standard condition. HBsAg and HCV antibodies were determined 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 who was an employee of health and treatment department of the prison, b) a blood sampler who was a staff of a university of medical sciences.
Statistical analysis
Data were analyzed using the survey package in Stata/SE 14.0. The weighting, clustering, and stratification of the survey design were applied for the main data with 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 the data on 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 entered into the multivariate model.