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Universal Screening or Prophylactic Treatment for Chlamydia trachomatis Infection Among Women Seeking Induced Abortions: Which Strategy Is More Cost-Effective?

Chen, Shumin MD, MPH*; Li, Jianhong MD*; van den Hoek, Anneke MD, PhD

Sexually Transmitted Diseases: April 2007 - Volume 34 - Issue 4 - p 230-236
doi: 10.1097/01.olq.0000233739.22747.12
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CHLAMYDIA TRACHOMATIS INFECTION IS ONE of the most prevalent sexually transmitted diseases (STDs) in many parts of the world, including both developing and developed countries.1 It is estimated that 50 to 70 million people are newly infected worldwide each year2 and 3 million are infected in the United States.3C. trachomatis infection has also been found to be the most prevalent STD in a national survey conducted in China, although it is not notifiable.4

It is estimated that 50% to 90% of chlamydial infections in women are asymptomatic.5 If untreated, they can lead to many complications and sequelae in infected women, including pelvic inflammatory disease (PID), ectopic pregnancy, tubal infertility, and chronic pelvic pain.6,7C. trachomatis infection can be transmitted by women to male sexual partners, leading to urethritis and epididymitis, and to neonates, leading to neonatal pneumonia and conjunctivitis.8 The infection and its complications and sequelae claim a huge amount of budget in the public health sector and cause the loss of healthy life and money for the women infected.9 Therefore, screening and treatment for women found infected have been recommended and implemented in many STD control programs,10–14 reducing complications in the United States and Sweden.14,15

Two types of strategies have been used to screen for chlamydial infections: universal screening and selective screening. To deal with C. trachomatis infection in a given population, a third strategy is prophylactic treatment with proper antibiotics. A number of studies have assessed the cost-effectiveness or cost–benefit of screening for C. trachomatis in populations with diverse rates of chlamydial infection rates supporting more informed decision-making.16–22 However, economic analysis to assess the cost-effectiveness of screening or prophylactic treatment for chlamydial infections in women seeking induced abortions has rarely been conducted.23

We previously studied the prevalence of sexually transmitted infections (STIs) and risk factors among women seeking induced abortions (suction type of early abortion) in 2 family planning clinics in Jinan, the capital of Shandong province, aiming to set up criteria for selective screening program or prophylactic strategy.24 Chlamydial infections were identified in 4.8% of women using polymerase chain reaction (PCR) assay, and 2 factors (vaginal discharge and cervical erosion) were found to be associated with the infection. However, the sensitivity and positive predictive value (28.1% and 7.9%, respectively) for the diagnosis of C. trachomatis were too low to be used for the selective screening. The remaining 2 options were either universal screening or preoperative prophylactic treatments for all women seeking induced abortions. We therefore conducted a cost-effectiveness analysis based on the results of the base scenario study, aiming to make recommendations for the health authority and health providers through evaluating the incremental cost-effectiveness of universal screening strategy (with PCR assay) and prophylaxis with azithromycin versus no intervention.

Materials and Methods

Study Population

Our previous study of STI prevalence among women seeking induced abortions from November 1999 to June 2000 was conducted with financial support from and approval by the EU-China training project on STD/HIV/AIDS.24 Briefly, all women seeking induced abortions, no matter what the reason, were recruited to participate in a cross-sectional study conducted at 2 urban family planning clinics. Collection of information on demography, history of gynecology and obstetrics, condom use, and sexual factors using a structured questionnaire was followed by collection of vaginal/cervical swab samples and venous blood samples for the diagnosis of STIs. The tests for C. trachomatis and Neisseria gonorrhoeae were performed with a PCR assay using a modified pooling method described by Peeling et al.25 Among 2,020 women included in the final analysis, the prevalence of STIs was 4.8% for C. trachomatis, 0.4% for N. gonorrhoeae, 2.5% for trichomoniasis, and 3.4% for bacterial vaginosis 503 were tested for syphilis, of whom 5 had a positive Treponema pallidum particle agglutination and 787 were tested for HIV, of whom one was positive.

Model Design

A computer-based decision analytic model (DATA 4.0; Treeage Software, Williamstown, MA) was developed to evaluate and compare the cost and disease outcomes associated with no intervention, universal screening, or prophylactic treatment. The model was constructed in a hypothetical cohort of 10,000 women seeking induced abortions, and key structural components of the tree are shown in Figure 1. Medical outcomes include, in women, cases of PID, chronic pelvic pain, ectopic pregnancy, and infertility; and in male sex partners, cases of urethritis and epididymitis. Because the study population was women seeking induced abortions, neonatal pneumonia and neonatal conjunctivitis were not included in the analysis. Total direct costs were defined as the universal screening costs or the prophylactic treatment costs and the medical costs of sequelae in women and male sex partners.

Fig. 1
Fig. 1:
Decision analysis model for cost-effectiveness comparison of 3 different strategies (universal screening and prophylactic treatment vs. no intervention).

The analysis took the perspective of the healthcare system rather than the patient. Several of the estimates were derived from our own data collection such as the prevalence of chlamydial infection.24 The remainder of the estimates was derived from published data, government documents, and experts' opinions collected with a survey with a questionnaire. The exact intervals between the chlamydial infection and the development of sequelae were unclear. For purpose of this analysis, we assumed that all cases of acute PID would occur with 12 months of infection.26 Chronic pelvic pain and ectopic pregnancy were assumed to occur in the second year and fifth year, respectively, after infection. Infertility treatment costs were incurred in the 10th year after the chlamydial infection. All costs were adjusted to the year 2002 in RMB (U.S. $1 = 8.2 RMB). Future costs discounted at a rate of 3% per year. We report total cases of PID and epididymitis prevented, the total costs saved, average cost of per case of PID prevented, and the incremental costs of each strategy compared with the no-intervention strategy.

Probability Estimates

We derived the reference case model parameters from previous studies in the literature.16–21,27 We hypothesized a cohort of 10,000 women annually seeking induced abortions in Jinan City, Shandong province each year in which the prevalence of chlamydial infection would be 4.8%.24 In women who do not seek abortion, it is estimated that 30% of women infected with C. trachomatis would develop PID, 40% of which would be asymptomatic. Under the condition of induced abortion, we estimated that a higher proportion of infected women would develop PID: 63%.28 Among the women with a history of PID, 18% would develop chronic pelvic pain or chronic PID, 8% would experience an ectopic pregnancy, and 12% would be infertile. For this last population, we assumed that 25% of women with tubal factor infertility would go for treatment.17 Of the women with PID, 86% would be treated in an outpatient clinic and 14% would need hospitalization. The probability of transmission of chlamydial infection from infected female to male sex partner would be 68%. If untreated, 40% of these men would develop urethritis and 2% would develop epididymitis.

The sensitivity and specificity of PCR for the detection of C. trachomatis were 87.6% and 99%, respectively. Gastrointestinal tract reactions (0–17%, mean: 11%) were the most common azithromycin-related side effects, and the majority was mild or moderate severity. Because they did not add to direct costs, treatment side effects costs were omitted from analysis (Table 1).

TABLE 1
TABLE 1:
Probability Estimates for Decision Analysis

Cost Estimates

The costs incorporated into the model were medical costs associated with the diagnosis and treatment of chlamydial infection and those associated with PID and its sequelae. The treatment of male sex partners who were infected with C. trachomatis and who developed symptoms and complications were also included in the model (Table 1). In this analysis, only direct costs were considered.

Today in China, public health services are government-subsidized, but the clients have to pay charges for their health services. Diagnosis and treatment criteria for PID and its sequelae are unavailable in China, and the costs may vary from hospital to hospital. To obtain this information, we conducted a survey in 3 facilities of different levels: a city family planning clinic, a district general hospital, and a provincial hospital. Twelve gynecologists were asked to give their opinions and the resulting average values were used in the calculation of the costs. The regimens for the treatment of C. trachomatis infection, urethritis, and epididymitis were taken from/reflect the National Guideline of STD Management issued by the Ministry of Public Health, China. The prophylactic strategy used a single 1-g dose of oral azithromycin (Table 2). The nonmedical direct costs such as transportation and loss of salary are not included in the analysis.

TABLE 2
TABLE 2:
Cost Estimates

Sensitivity Analyses

Sensitivity analyses were performed to evaluate uncertainty in the model. After one-way sensitivity analyses were conducted on all parameters, detailed one-way and 2-way sensitivity analyses were conducted on the prevalence of infection and the cost of the PCR test or the cost of drugs. These 3 variables showed the greatest impact on overall strategy cost and effectiveness.

Results

As shown in Table 3, 480 women would be infected by C. trachomatis in a hypothetical cohort of 10,000 women undergoing induced abortions, of which 302 women would develop PID, 24 ectopic pregnancy, and 36 infertility when no intervention was undertaken. In addition, 131 sex partners of the women would develop urethritis and 7 epididymitis. Comparing the 3 strategies, prophylaxis was the most effective, preventing 96% more PID cases than the no-intervention strategy. Whereas universal screening prevented 84% more PID cases than no intervention. Comparing the 2 active strategies, prophylactic strategy can prevent 57 more C. trachomatis-infected cases and 36 more PID cases over universal screening.

TABLE 3
TABLE 3:
Strategy Effectiveness: Complications and Sequelae Prevented

Costs associated with the three strategies are presented in Table 4. The total costs in prophylactic strategy and screening strategy were, respectively, 411,525 RMB (US $50,186) and 1,068,119 RMB (US $130,258) more than the total cost of no intervention (296,827 RMB). However, complications cost dramatically more with no intervention than with prophylaxis universal screening, which could effectively prevent the development of sequelae. The prophylactic strategy would cost 114,698 RMB more than the no-intervention strategy in preventing 289 more PID cases, with 397 RMB (US $48), on average, spent to prevent one PID case. Compared with prophylaxis, universal screening prevented 253 cases of PID—36 less than prophylaxis—while costing 656,594 RMB more than prophylaxis. According to the rule of incremental cost-effectiveness ratio analysis, the universal screening strategy was dominated by the prophylactic strategy.

TABLE 4
TABLE 4:
Cost-Effectiveness: Savings and Pelvic Inflammatory Disease (PID) Prevented

Sensitivity Analyses

Cost Analysis and Effectiveness Analysis

We conducted one-way and 2-way sensitivity analyses to examine how the prevalence of chlamydial infection of women seeking induced abortions affected the costs in universal screening and prophylactic treatment (Fig. 2 through Fig. 5). As prevalence increased, total program costs for the 3 strategies changed in their comparative relationship. At a prevalence of 2%, the costs for no intervention, universal screening, and prophylaxis were 123,564 RMB, 1,030,580 RMB, and 404,943 RMB, respectively. At a prevalence of 6%, the costs for no intervention, universal screening, and prophylaxis were 370,692 RMB, 1,083,739 RMB, and 414,827 RMB, respectively. When the prevalence increased to 7%, the total cost for no screening/treatment became more expensive than prophylactic treatment, and when the prevalence increased to 20.8%, the cost for no screening/treatment became more expensive than universal screening (Fig. 2).

Fig. 2
Fig. 2:
One-way sensitivity analysis on the impact of varying the prevalence of Chlamydia trachomatis on overall strategy cost.
Fig. 3
Fig. 3:
One-way sensitivity analysis on the impact of varying the cost of polymerase chain reaction on average strategy cost.
Fig. 4
Fig. 4:
Two-way sensitivity analysis on the impact of varying Chlamydia trachomatis prevalence and the cost of polymerase chain reaction on overall strategy cost.
Fig. 5
Fig. 5:
One-way sensitivity analysis on the impact of varying the cost of azithromycin on the incremental cost-effectiveness of the 3 strategies.

Figure 3 shows the effect of varying the cost of the PCR assay on the total strategy cost. At the base scenario prevalence of 4.8%, the cost for screening with PCR exceeded the cost of no intervention, when the PCR cost rose above 23 RMB per assay. When it reached 36 RMB, the cost for universal screening became higher than the cost for prophylaxis. However, the cost for prophylaxis was higher than the cost of universal screening when the price of 1 g azithromycin rose above 110 RMB. When the price of azithromycin was above 29 RMB, the cost for prophylaxis would exceed the no-intervention strategy.

The results of 2-way sensitivity analysis (Fig. 4) show the effects on total strategy costs of both the prevalence of chlamydial infection among women seeking induced abortions and the cost of the PCR assay. When both the chlamydial infection prevalence and the PCR cost were low, the cost for universal screening was lower than the cost for prophylaxis. When the cost of azithromycin decreased and the prevalence of chlamydial infection increased, the prophylaxis became less expensive than universal screening. However, whether prevalence of chlamydial infection rose or fell among the women seeking induced abortions, the prophylactic treatment strategy prevented the most PID cases of the 3 strategies. No variation in the total costs of PCR or azithromycin changed the overall outcome (PID cases prevented) of the program effectiveness.

Analysis of Incremental Cost-Effectiveness Ratios

Figure 5 shows how incremental cost-effectiveness ratios changed as the cost of prophylactic medicine increased. If the cost of azithromycin was less than 122 RMB, universal screening was dominated by prophylactic treatment. The incremental cost-effectiveness ratio of prophylaxis was higher than universal screening if the cost of azithromycin was 122 RMB or above. When we analyzed the effects of the C. trachomatis prevalence on the incremental cost-effectiveness ratios, we found that variation in prevalence had no effect on the incremental cost-effectiveness ratios of the 3 strategies. The prophylactic treatment would be the most cost-effective of the 3 strategies, whatever the C. trachomatis prevalence might be.

The incremental cost-effectiveness ratio of the 3 strategies changed with the cost of PCR. When assay cost was less than 33 RMB, the incremental cost-effectiveness ratio of the prophylaxis was higher than universal screening, meaning that the cost for preventing one additional PID case was higher in prophylactic strategy than in the screening strategy. If the cost of PCR was 33 RMB or above, the screening strategy was dominated by prophylaxis; thus, the prophylactic treatment strategy was the most cost-effective of the 3 strategies (i.e., less expensive with more PID cases prevented).

Alternative Scenarios

We also performed the incremental cost-effective analysis on various scenarios that had important analytic limitations. These scenarios included the proportion of complications both in women and men and the cost, sensitivity, and specificity of the PCR assay and efficacy rate of azithromycin. These did not change the findings of the baseline effectiveness analysis.

Discussion

Programs designed for the early identification and treatment of asymptomatic chlamydial infections have the potential to prevent involvement of the upper reproductive tract and transmission to sexual partners and neonates, averting the medical costs associated with the management of complications and sequelae.10 Women attending a clinic for an induced abortion could be a target group for such programs on this and other STDs because of the diverse gynecologic symptoms/signs in this group and the danger that surgery might spread infection into the urinary tract.29

The routine use of antibiotics at surgical abortion is controversial,30–33 although evidence based on meta-analysis revealed a substantial protective effect of antibiotics in all subgroups of women undergoing therapeutic abortion, even women in low-risk groups.34 Some authors30,31 have advocated universal preoperative antibiotics, but others have recommended them only in women at high risk of infection32,33 and even preferred screening, with treatment only of those found infected, because of the fear that prophylactic treatment without screening would waste time and resources33 and could lead to antibiotic resistance from overtreatment.23 A recent cost-effectiveness simulation study of women seeking early suction abortion has demonstrated that risk-based antibiotic prophylaxis is the most cost-effectiveness strategy compared with other strategies, including universal prophylaxis.23 Unfortunately, we could not establish any selection criteria for our targeted population of low-risk women seeking induced abortion, because both symptoms/signs and risk behaviors are not sensitive with very low positive predictive values of vaginal and cervical infections.24

Our results show that, compared with universal screening, the prophylactic treatment strategy is the most effective strategy, preventing 96% more PID cases than no intervention. Although universal screening could prevent 84% more PID cases than no intervention, prophylaxis could prevent additional 36 PID cases and save 656,594 RMB over the universal screening strategy. If we consider all the complications and sequelae of chlamydial infection for women and the infection and sequelae in male sex partners, prophylaxis has even more benefit. Furthermore, its simplicity and the high efficacy of oral azithromycin at one dose of 1 g orally compares well with universal screening, which requires complicated and costly laboratory support and highly trained personnel.23 Another benefit of universal treatment for women seeking induced abortion in a family planning setting is that this regimen is effective in treating N. gonorrhoeae,35 often concomitant with C. trachomatis infection.

Like with any other studies on cost-effectiveness analysis, our study has some limitations. First, the risk of occurrence of the PID after induced abortion has not been well established. In our analysis model, we assumed a rate of 63% PID in postabortion,28 which may be overestimated. More sound evidence is needed to confirm it. Van Valkengoed et al36 argued that an overestimation of the current complication rates was likely compared with the data obtained from local registrations, especially for the populations with a low prevalence. A review revealed that the incidence rates of PID after surgical procedure for abortions among women infected with C. trachomatis vary from study to study, ranging from 27% to 72%.37 However, our sensitivity analysis showed that the estimate of PID in postabortion did not affect the results (data are not presented), because the total cost of tests in the screening exceeds the total cost of prophylaxis, and the prophylactic strategy prevents more cases of PID than the screening strategy (Tables 3 and 4).

The second limitation, as already pointed out, is inherent to modeling complex events based on parameters and probabilities derived from the medical literature and expert opinion. In reality, such factors may widely vary geographically and by healthcare setting, especially in China where the healthcare system is benefit-drawn, which means the doctors' salaries and hospital costs are largely recouped from the patient's fee. Third, as also mentioned, the costs for the treatment of complications and sequelae are unavailable in China. For example, the costs for the treatment of PID vary from setting to setting and vary among the experts consulted in our survey. Fourth, we did not calculate the indirect cost, which offset the financial input for the care of the health problem for the women. However, inclusion of indirect costs in our sensitivity analyses did not affect the general conclusions of the model (data are not presented). Finally, we did not address several uncommon but costly outcomes in which C. trachomatis may play a causative role such as premature labor, low birth weight and other outcomes for newborns, and postpartum endometritis, because we could not exactly calculate the proportion of abortion-seeking women who may later want to have babies.

Although prophylactic strategy is more effective (preventing more PID cases and costing less) than universal screening in our analytic model, it does not permit the tracing or treatment of male sexual partners.38 The number of sequelae avoided by prophylaxis is therefore decreased, because women receiving the prophylaxis when chlamydia-positive (with or without their knowledge) may only have a short-term benefit; if still at risk from an infected partner, they can soon be reinfected. In contrast, a screen-and-treat strategy policy can encompass partner tracing, thus preventing/minimizing reinfection of women. Another advantage of the screen-and-treat strategy for C. trachomatis is that antibiotics are given only to the small proportion of women found to be infected, avoiding unnecessary administration of antibiotics to a large proportion of women undergoing an abortion procedure.

In conclusion, to prevent postabortion complications of women in China, we recommended that this group receive universal prophylactic treatment for C. trachomatis infection with a single oral dose of 1 g azithromycin. Combining this prophylaxis with administration of metronidazole can also be considered in circumstances/areas where bacterial vaginosis is prevalent.

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