| BackgroundGenital Chlamydia trachomatis(CT)is one of the sexually transmitted infections(STIs)with a high prevalence,CT is transmitted mainly through direct sexual contact,indirect sexual contact,or similar sexual behaviors.Complications of CT in females include pelvic inflammation disease(PID),chronic pelvic pain,ectopic pregnancy,and infertility.The sequelae of CT in males include urethritis and epididymitis.The complications of CT affect the health and quality of life among infected persons.In recent years,the prevalence of CT has increased rapidly worldwide.According to STI surveillance reported by World Health Organization(WHO)in 2015,the number of infected patients in the world was 130.9 million in 2012,which increased 29%compared with 2005.Thus,prevention of CT has attracted extensive attention from the WHO and public health workers in various countries.Estimation of the prevalence and disease burden of CT is mainly based on the surveillance system;however,the CT surveillance system canot measure the true STI burden because a majority of CT infections are asymptomatic.Indeed,it is more challenging to diagnose asymptomatic patients in dermatology and STI clinics.Furthermore,reported data are often frequently misclassified or duplicated.Thus,the reported cases may only represent a small percentage of the actual number of cases.Data from surveillance system can provide limited information for the design of a CT control strategy.A population-based cross-sectional study with a large sample size could estimate the accurate disease distribution,risk factors,and associated medical costs,which in turn would provide scientific evidence for CT-specific control;however,little information has been available for the prevalence of CT among the general population in mainland China in the past decade.In 1999-2000,Parish and his research group from Chicago University conducted the first population-based cross-sectional study to estimate the prevalence of CT among the general population in China 20-64 years of age.Franceschi from International Agency for Research on Cancer conducted another population-based cross-sectional study in Shanxi Province,China in 2004 to determine the prevalence of CT among female residents 15-44 years of age.There were some limitations,however,involving the two published studies.First,those studies were conducted before 2004,but the incidence of STIs increased rapidly since 2004.Moreover,the attitude towards sex has also changed significantly in recent years.Thus,the two studies provide limited information with respect to CT control.Second,the sample size of the studies was relatively small.Specifically,the sample size of the survey carried out in Shanxi Province was only 399,which could not produce a precise estimation.We conducted a population-based cross-sectional survey with a complex sampling method to determine the prevalence of CT infections among the general population 18-49 years of age in Shandong Province in 2016.The estimated sample size was 8074 individuals.Nucleic acid amplification tests with the advanced Roche Cobas 4800 CT Assay(Roche Molecular Systems,Inc.)was used to detect urine for CT infection.This study sampled a representative population to give an accurate and updated estimation of the CT disease burden.Based on results of cross-sectional studies,several countries from North American or European areas have conducted CT screening programs since 2000.This study can provide informative evidence for designing of a CT control strategy in Shandong Province.In addition,estimation of medical costs was informative for the allocation of health resources;however,the medical cost associated with CT infections has not been estimated in China.The US Center for Disease Control and Prevention estimated the medical cost of CT infections among local residents in 2008.The total medical cost of CT infections was 517 million dollars(95%CI,258 million-775 million dollars),which was higher than the medical costs of 7 other types of STIs.An estimation of CT medical costs provides important reference data for the allocation of health funding for STIs in the United States.This study will the estimate medical costs of CT infections for the first time among the general population 18-49 years of age in Shandong,and provide scientific evidence for cost-effective evaluation of CT screening strategy implementation.Objectives1.Update the prevalence of CT infections among the general population worldwide through a meta-analysis.2.Determine the prevalence and risk factors for CT infections among the general population in Shandong Province.3.Estimate the medical costs of CT infections among the general population in Shandong Province.Methods1.The prevalence of CT infections and 95%confidence intervals(CIs)among the general population through a meta-analysis were calculated.Heterogeneity was evaluated with a Q test and expressed with an I2.An I2>50%indicated high heterogeneity among the included studies;the prevalence was pooled using a random effects model.An I2<50%indicated low heterogeneity among the included studies;the prevalence was pooled using a fixed effects model.Meta-regression was used to determine the source of heterogeneity.The trim and fill method and funnel plot were used to evaluate publication bias.2.This populationbased cross-sectional study used multi-stage complex sampling to select a representative sample from the general population in Shandong Province.The sampling process included 4 steps.First,Shandong Province was divided into 4 strata,and counties or urban districts were randomly sampled as primary sample units(PSUs)from each stratum.Second,Probability Proportionate to Size Sampling(PPS)was used to select towns and street districts as subunits from PSUs.Third,villages or communities were sampled using PPS sampling from subunits.Fourth,systematic sampling was used to choose eligible individuals.Thus,a representative sample was selected from the general population 18-49 years of age in Shandong Province.3.We applied weights to reduce bias at different stages.Sampling weights were adjusted at each sampling step to balance difference probabilities of selection.Non-response weights were used to reduce bias produced due to no participation of some individuals.Post-stratification weights were applied based on census figures of Shandong Province to further reduce selected bias and increase the representativeness of the sample.4.The prevalence of STIs was estimated based on the total weights of each individual.The 95%Cls of STIs were calculated using Taylor series linearization.After adjusting total weights,stratum,and PSUs,risk factors for STIs were explored using univariate and multivariate logistic regression.Variance inflation factor and system of eigenvalues were used to examine multicollinearity among covariates.We analyzed data using survey and surveylogistic processes in SAS 9.3.5.We calculated the medical costs of CT infections and associated sequelae among the general population in Shandong based on the estimated prevalence of this study and research methods of health economics.The incidence of difference sequelae was also adopted from published studies.Results1.The prevalence of CT infections among the general population worldwide was determined through a meta-analysis.Twenty-seven studies from 25 countries were included in the meta-analysis.The total number of included participants was 71,940.The pooled prevalence of CT infections among the general population was 3.2%(95%CI,2.6%-3.7%).The pooled prevalence of CT infections for males was 2.7%(95%CI,1.9%-3.5%),which was higher than females(3.3%,95%CI,2.6%-4.1%)(?2=16.57,P<0.01).Differences in the prevalence of CT infections from WHO 5 areas were significant(?2=2.42,P<0.01).Residents from the North American region had the highest prevalence of CT infections(4.6%,95%Cl,3.2%-6.0%),followed by the African(3.2%,95%CI,1.8%-4.6%),European(2.7%,95%CI,1.9%-3.5%),and Western Pacific(2.4%,95%CI,1.4%-3.4%)regions.Residents from the Southeast Asia region had the lowest prevalence of CT infections(1.2%,95%Cl,0.7%-1.6%).No published studies was retrieved from the Eastern Mediterranean area.2.The prevalence and risk factors for CT infections among the general population in Shandong Province were determined.A total of 7203 participants were included in the analysis in the cross-sectional study,among whom 167(77 males and 90 females)tested positive.The weighted prevalence of CT infections among the general population 18-49 years of age was 2.7%(95%CI,1.6%-3.8%)for men and 2.3%(95%CI,1.5%-3.2%)for women(2.5%,95%CI,1.9%-3.2%for men and women combined).We estimated that there were approximately 1,263,000(95%CI,774,000 to 1,753,000)CT infections in Shandong Province,670,000(95%CI,400,000-956,000)CT infections in men and 587,000(95%CI,379,000-797,000)CT infections in women.For males,the highest prevalence of CT infections was in those 18-24 years(4.1%,95%CI,0-8.8%)of age;the prevalence decreased with age(P=0.02).Females 18-34 years of age(3.2%,95%CI,1.8%-4.6%)had a higher prevalence of CT infections than the other age groups(P=0.02).No difference in prevalence of CT infections existed among participants from the northwest,middle,eastern,and southern areas of Shandong Province for males(P=0.57)and females(P=0.78).Similarly,no difference in prevalence of CT infections existed between individuals from urban and rural areas(P=0.42).Based on the multivariate surveylogistic,the risk factors for CT infections was first intercourse before 20 years of age(OR 1.76,95%CI 1.05-2.94)and having two or more lifetime sex partners(OR 2.09,95%CI 1.10-3.94).In women,being unmarried/divorced/widowed(OR 3.64,95%CI 1.63-8.13)and having two or more lifetime sex partners(OR 3.66,95%CI 1.07-12.48)was associated with CT infections.3.The medical costs for CT infections among the general population 18-49 years of age in Shandong Province was 273 million(range,172 million-374 million)China RMB in 2016,corresponding to a cost of 348 RMB(range,339-361 RMB)for each female case and 102 RMB(range,97-108 RMB)for each male case.When the assumed prevalence of CT infections was at the lower limit of the 95%CI,the medical costs decreased by approximately 100 million RMB.When the assumed CT prevalence was at the upper limit of the 95%CI,the medical costs increased by approximately 100 million RMB.When the assumed asymptomatic rate of CT infections was 90%,the medical costs increased by approximately 20 million RMB.When antigen detection was used as the method of detecting CT detections,the medical costs decreased by approximately 10 million RMB.Conclusions1.This study showed heterogeneity regarding the prevalence of CT infections in different genders and regions through a meta-analysis.The prevalence of CT infections in females was higher than that in males.Residents from North American regions had the highest prevalence of CT infections,while residents from Southeast Asia had the lowest prevalence of CT infections.Thus,the design of CT prevention strategy and allocation of health funding should be based on different local conditions.2.Males 18-24 years of age and females 18-34 years of age were defined as the high-risk groups for CT infections,which should be the focus when implementing a CT control program.3.Individuals who had several sexual partners,had first sexual intercourse before 20 years of age and who were unmarried/divorced/widowed were at high risk for CT infections.Thus,sexual public education should admonish individuals to delay their sexual debut as much as possible and to avoid multiple sex partners.In addition,unmarried/divorced/widowed individuals should receive more attention when designing a CT control strategy.4.This study indicated that CT infections lead to substantial medical costs among the general population in Shandong Province.The medical costs assiciated with CT infections were mainly affected by the prevalence.To decrease the prevalence and medical costs of associated with CT infections,the government should provide sufficient funding to guarantee the implementation of a CT control program.Innovations1.This study provided evidence-based data for all population-based studies estimating prevalence of CT infections worldwide.Subjects of previous meta-analysis on prevalence of CT included community population,clinic patients,secondary sampling population and individuals who were followed up,which resulted in imprecise pooled prevalence.This study included studis focused on general population only,which updated prevalence of CT among general population worldwide and provide informative information for CT control.2.This study was the first population-based cross-sectional study with large sample size to estimate prevalence of CT in mainland China since 2000.The sample size of this study was 8074 individuals.This study adjusted weights in different stages of multistage complex sampling to estimate prevalence of CT;taylor series linearization was used to calculate variance of prevalence;the most advanced noninvasive nucleic acid amplification testing technology(Roche Cobas 4800 CT q-PCR method)was used to test CT DNA.Thus,this study obtained precise prevalence estimation and provided evidence for the design of CT control policy.3.This study found that the prevalence of CT infections in young adults 20-24 years of age has increased rapidly since 2000 by longitudinal comparison;CT was highly prevalent among males 18-24 years of age and females 18-34 years of age by horizontal comparison.The findings of the above key population provided scientific evidence for the specific intervention of CT infections in Shandong Province. |
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