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Hepatitis B, Risk factors, Vaccination, Logistic models, Machine learning, What&,rsquo s Known The epidemiology of hepatitis B virus (HBV) infection in the pre-vaccine era has been studied widely, but few studies have been conducted since the introduction of HBV immunization. Different studies and countries have reported various factors affecting the morbidity and prevalence of the disease. What&,rsquo s New This is the first study in Iran to investigate the factors associated with HBV infection, 25 years since the launch of national HBV immunization. National HBV immunization has reduced hepatitis B infection and the effects of its risk factors such as a family history of hepatitis B. IntroductionHepatitis B is a viral infection and one of the main health problems in the world. 1, The prevalence of Hepatitis B virus (HBV) varies across different countries and regions, and this virus can increase the risk of cirrhosis and hepatocellular carcinoma. 2,- 5, Most cases of HBV infection have been reported from Asia, the Middle East, and Africa. 6, In countries with low socioeconomic status or poor health conditions, it appears that the majority of cases are transmitted from mother to child and happen in young children. The possibility of chronic HBV infection is greater in those infected in the neonatal period or childhood, 7, and about 25% of individuals with chronic infection die as a consequence. 6, Vaccination is an essential way of controlling and preventing the transmission of HBV infection. 8, The mass vaccination of infants and children in the context of the Expanded Program on Immunization (EPI) was recommended by the World Health Organization in 1991. 9,, 10, The complications of HBV infection may not be treated at the end stages, but HBV vaccination, currently implemented in many countries, can reduce the incidence and mortality of this infection. 11,, 12, It has been shown that immunization against HBV within the first 24 hours of life and completing three doses during infancy and childhood play an important role in preventing HBV infection. 13, Based on the results of previous studies, various factors such as high-risk sexual behaviors, intravenous illicit drug use, 14, a family history of the disease, 15, education, and socioeconomic status 16, can be associated with HBV infection. The results of a study in Pakistan showed that household contact sexual contact and a history of blood transfusion and its components, surgery and dental works were the main risk factors for the increased prevalence of HBV infection. 17, Machine learning has been used for the prediction and classification of various aspects of HBV infection. 18,- 20, For instance, a previous investigation employed this modality as a decision-support system to enhance the stage diagnosis performance of HBV. 18, Various machine learning methods are currently in use for data classification. 19, Such methods are drawn upon in the fields of statistics, computer science, and artificial intelligence by their ability to create algorithms capable of data-based classification and prediction. 21, The epidemiology of HBV infection in the pre-vaccine era has been investigated extensively, but only a few studies have been conducted since the introduction of HBV vaccination. 22, Awareness of the natural history and factors influencing the progression of HBV infection can be helpful in its management and treatment. Previous research has shown various factors affecting the morbidity and prevalence of HBV infection in different countries. 18,- 20, In Iran, the national HBV immunization program was launched by the Iranian Ministry of Health and Medical Education in 1993. 23, Nevertheless, given the current dearth of data on HBV infection and its associated factors since the implementation of the aforementioned immunization program in Iran, we utilized logistic regressions and machine learning methods to explore the association of HBV infection with routine vaccination and other effective factors. Patients and MethodsStudy PopulationThe current cross-sectional study, conducted in Shiraz (Iran), evaluated 2720 individuals for HBV infection and the factors affecting its incidence, especially national HBV immunization. This study was approved by the Research Ethics Committee of Shiraz University of Medical Sciences (Ethics Code, IR.SUMS.REC. 1397. 437). Data were collected through data-collection forms and blood sampling by trained interviewers and laboratory staff, correspondingly.According to the studies used by the Centers for Disease Control and Prevention (CDC), 24, the disease rates in vaccinated and unvaccinated individuals were 4.1% and 10.7%, respectively. Therefore, according to the following formula at a 95% confidence interval (CI) and a power of 90%, we estimated a required sample size of at least 2258 individuals. n = ( Z 1 - &,alpha &,frasl 2 + Z 1 - &,beta ) 2 ( p 1 q 1 n 1 + &,#981 0 2 p 2 q 2 n 2 ) ( p ^ 1 p ^ 2 - &,#981 0 ) 2 In this formula, p ^ 1 and p ^ 2 represent disease rates in vaccinated and unvaccinated individuals, p 1 and q 1 represent the estimates of conditional maximum likelihood ratios, and &,#981 0is equal to p 1 / p 2 . 25, The study samples were selected from individuals who referred to the only three health centers in Shiraz in 2017. Since the mandatory premarital screening tests in Iran require routine blood sampling for all individuals, we selected the study participants from among those undergoing mandatory screening to reduce problems relating to blood sampling. HBV infection tests are not routinely performed as a part of the mandatory premarital screening tests consequently, after obtaining consent from the individuals, we took blood samples concurrently with the mandatory premarital screening tests. Inclusion and Exclusion CriteriaOn account of the year of the implementation of the infantile HBV vaccination program in Iran (1993) and also its high coverage (close to 100%), 23, vaccinated individuals were selected from among those born in 1994 and after and unvaccinated individuals from among those born in 1992 and before. Individuals who did not consent to participate in the study and those having a non-Iranian nationality were excluded from the study. In the unvaccinated group, individuals whom themselves received an HBV vaccine for any reason were excluded from the study.Data Collection Written informed consent was obtained from all the study participants after they had been given complete explanations about the goals and methods of the study. Thereafter, a blood sample of 4 mL was drawn from each person into an anticoagulant tube (Guangzhou Improve Medical Instruments Co, Ltd, Guangzhou, China) and transferred to the reference laboratory. For the transport of the samples, the serum samples were stored in a freezer (Sanyo, Japan) at &,minus 20 &,deg C and then transferred to the lab with ice bags as soon as possible.Definition of the OutcomeHBV infection status, determined via Hepatitis B surface antigen (HBsAg) and anti-hepatitis B core antibody (HBc Ab) tests (Dia.Pro Diagnostic Bioprobes Srl, Italy), was considered to be the outcome. If either of these markers after blood sampling and serum separation was positive, the person was considered HBV infection positive. 22,, 26,, 27, Associated FactorsFactors such as demographic variables, the potential risk factors of the disease, and a history of national HBV vaccination were investigated. In addition, a family history of HBV infection, comprising a history of HBV infection in father, mother, sister, brother, spouse, and child high-risk behaviors such as tattoos, high-risk sexual contacts (e.g., extramarital sex), and intravenous illicit drug use a history of surgery or dental work and a history of the transfusion of blood or any blood product were measured. Statistical AnalysisThe data were analyzed with R software (version 3.5.2), via multivariate logistic regressions as a classical model and a recursive partitioning algorithm comprised of a conditional tree (using the &,ldquo party&,rdquo package), a conditional forest (using the &,ldquo party&,rdquo package), and a random forest (using the &,ldquo randomForestSRC&,rdquo package) as a new learning method. In the regression model, all the variables were analyzed using multivariate logistic regressions via the &,ldquo Inter&,rdquo method. The logistic regression and machine learning methods were utilized to achieve the following goals, to determine the factors associated with HBV infection, to predict HBV infection based on the related variables, and to determine the importance of these variables. The goodness of fit of the models was compared using accuracy and Brier score indices. In the conditional and random forest methods, the mean decrease Gini index was employed to measure the importance of variables in the classification, with a higher value of this index representing its higher importance. 28,, 29, In all the tests, the level of significance was considered below 0.05.The conditional tree divides the population based on the related factors, resulting in homogeneous subsets of the population. The advantages of the conditional tree method in comparison with regression models include its ability to deal with collinear variables and big data. 30,, 31, This algorithm provides a P value useful to determine the level of confidence that can be obtained in each division. 32, The conditional forest and the random forest are two types of forests applied to calculate the importance of variables. 30,, 33, The random forest method was recently proposed for the prediction and selection of variables,33 and its categorization can usually reduce the over-fitting problem often occurring in an individual decision tree. 18, ResultsThe present study recruited 2720 individuals, of whom 194 (7.1%) were HBV infection positive. The mean age of the participants was 26.9&,plusmn 5.82years. Additionally, 85 (3.3%) cases had a history of HBV infection in their families, 1541 (56.6%) were women, and 1273 (46.8%) were vaccinated (table 1,).VariableFrequency (%)TotalVaccinatedUnvaccinatedGenderMale1184 (43.44)309 (24.27)872 (60.26)Female1541 (56.56)964 (75.73)575 (39.74)EducationPrimary or middle school190 (7.00)55 (4.33)134 (9.30)High school154 (5.67)89 (7.01)65 (4.50)Diploma970 (35.71)558 (43.98)409 (28.34)Academic/university1402 (51.62)567 (44.68)835 (57.86)OccupationSelf-employed854 (33.44)248 (20.91)602 (44.13)Homemaker585 (22.90)359 (30.30)226 (16.57)Student525 (20.56)468 (39.46)57 (4.18)Employee of the private or state sector590 (23.10)111 (9.33)479 (35.12)History of high-risk behaviorsYes1787 (66.56)822 (65.29)961 (67.63)No898 (33.44)437 (34.71)460 (32.37)History of HBV in family membersYes85 (3.31)45 (3.66)39 (2.93)No2478 (96.69)1186 (96.34)1290 (97.07)National HBV vaccinationYes1273 (46.80)--No1447 (53.20)--HBV, Hepatitis B virus |