Sexually Transmitted Diseases:
The Cost and Cost-Effectiveness of Expedited Partner Therapy Compared With Standard Partner Referral for the Treatment of Chlamydia or Gonorrhea
Gift, Thomas L. PhD*; Kissinger, Patricia PhD†; Mohammed, Hamish PhD, MPH‡; Leichliter, Jami S. PhD*; Hogben, Matthew PhD*; Golden, Matthew R. MD, MPH§¶
*Centers for Disease Control and Prevention, Atlanta, GA; †Tulane University School of Public Health and Tropical Medicine, New Orleans, LA; ‡The University of Trinidad and Tobago, Trinidad, West Indies; §University of Washington Center for AIDS & STD, Seattle, WA; and ¶Public Health Seattle-King County, Seattle, WA
Supported by the National Institutes of Health (Grant Number R01AI068107) (to M.R.G.).
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
Correspondence: Thomas L. Gift, PhD, Centers for Disease Control and Prevention, Division of STD Prevention, Atlanta, GA 30333. E-mail: email@example.com.
Received for publication April 13, 2011, and accepted July 18, 2011.
Background: Partner treatment is an important component of sexually transmitted disease control. Several randomized controlled trials have compared expedited partner treatment (EPT) to unassisted standard partner referral (SR). All of these trials found that EPT significantly increased partner treatment over SR, whereas some found that EPT significantly lowered reinfection rates in index patients.
Methods: We collected cost data to assess the payer-specific, health care system, and societal-level cost of EPT and SR. We used data on partner treatment and index patient reinfection rates from 2 randomized controlled trials examining EPT and SR for patients diagnosed with chlamydia or gonorrhea. Additional elements were estimated or drawn from the literature. We used a Monte Carlo simulation to assess the impact on cost and effectiveness of varying several variables simultaneously, and calculated threshold values for selected variables at which EPT and SR costs per patient were equal.
Results: From a health care system or societal perspective, EPT was less costly and it treated more partners than SR. From the perspective of an individual payer, EPT was less costly than SR if ≥32% to 37% of male index patients' female partners or ≥29% of female index patients' male partners received care from the same payer.
Conclusions: EPT has a lower cost from a societal or health care system perspective than SR and treats more partners. Individual payers may find EPT to be more costly than SR, depending on how many of their patients' partners receive care from the same payer.
Partner treatment is a longstanding and critical part of public health efforts to control the spread of curable sexually transmitted diseases (STDs).1 However, relatively few health departments in the United States routinely assure that the partners of persons with gonorrhea or chlamydia are treated. The failure to treat infected sex partners is known to be one factor underlying the persistence of high rates of STD in the United States.2 Unassisted standard partner referral (SR), in which STD patients are counseled to refer their partners for examination and treatment, is also the norm with private providers.3 In the late 1990s, the Centers for Disease Control and Prevention (CDC) and National Institutes of Health (NIH) funded 4 randomized trials to help define a new, low-cost approach to increase partner notification and treatment for gonorrhea, trichomoniasis, and chlamydia. These studies evaluated what is now referred to as expedited partner treatment (EPT) or patient delivered partner therapy. EPT typically involves giving infected patients medication for their sex partners. EPT increased the proportion of partners treated in all 4 trials, and 2 of the 3 trials evaluating EPT for gonorrhea or chlamydia found that EPT significantly reduced the risk of persistent or recurrent infection in index patients.4–7 Another trial in the United Kingdom found that EPT for partners of female patients with chlamydia improved partner treatment over SR, but did not find a significant difference in persistent or recurrent infection.8
EPT is permitted in some form in a majority of US states; however, but its use may not be widespread even where it is legal.9,10 One factor thought to limit widespread adoption of the intervention is cost. Some health plans have been reluctant to assume the costs of providing medication for sex partners who may not be in the same plan. In this analysis, we examine the cost of EPT for partners of patients diagnosed with chlamydia or gonorrhea.
MATERIALS AND METHODS
Cost data were collected in 2003 in EPT randomized controlled trials in King County, WA, and New Orleans, LA. Both trials have been previously described; both randomly assigned patients to receive either SR or EPT.5,6 In Seattle, male and female patients diagnosed with chlamydia or gonorrhea were contacted by the health department using case and laboratory reports.5 Index cases providing oral informed consent and randomized to EPT were able to pick up partner packs at selected high-volume clinics, participating commercial pharmacies, the Public Health Seattle-King County (PHSKC) STD clinic, or via direct mail. PHSKC staff contacted partners at patients' request. Partners of persons in the EPT arm could obtain partner packs at pharmacies, the PHSKC STD clinic, or via the mail. In New Orleans, men diagnosed with urethritis at a public STD clinic were invited to participate in the trial.6 Patients providing written informed consent and randomized to EPT were given up to 4 partner packs for their sex partners.
To determine the labor cost associated with conducting the SR and EPT interventions, staff collected time-motion data. Because the case and laboratory reports were used to facilitate contacting patients in the Seattle study, the time spent entering the reports was tracked, in addition to the time spent interacting with the patients. Staff in Seattle also tracked the amount of staff time used to contact partners and pharmacies, and assemble and deliver partner packets to pharmacies. Staff also kept track of all activities in time diaries for 1 week. The proportion of the day devoted to administrative activities was determined (this included activities like answering e-mail and shredding documents). Time spent on these administrative duties was apportioned to other activities as an overhead cost. In New Orleans, staff collected time-motion data to determine the staff time required to counsel patients. At each site, the time cost per enrolled patient was adjusted by the participation rate. Time spent in contacting patients not enrolled in the study was apportioned among those who did enroll to get a final time cost per patient enrolled. Differences in time spent on patients in EPT and SR were tested for statistical significance using t tests. We assumed that disease investigation specialists would be paid at the federal employee GS-9, Step 3 level and that supervisors would be paid at the GS-11 Step 3 level.11 Time-motion data collection procedures were approved by institutional review boards at the CDC.
Additional costs came from the literature or from data available from the study. These included estimates of the cost to treat partners and the cost of sequelae of chlamydial and gonococcal infection in women (pelvic inflammatory disease [PID] and its sequelae of chronic pelvic pain, ectopic pregnancy, and infertility).12–17 The upper bounds for partner examination and treatment costs were taken from studies of the cost of care for chlamydia and gonorrhea among privately insured persons and were selected to depict the cost structure private providers might face when assessing EPT and SR. The percentage of partners treated in each arm was based on index patient self-report. Because a proportion of partners treated through EPT may also have visited a health care provider after receiving a partner pack, a variable controlling for this was included. Estimated productivity losses associated with health care visits and sequelae were drawn from the literature.18–20 Costs were adjusted to 2008 US dollars using the Consumer Price Index for All Urban Consumers (productivity costs) and the Medical Care component of the CPI (costs of testing, treatment, sequelae, and clinical health care visits).21
We used multiple cost perspectives. The baseline used a health care system perspective, including all direct medical costs for counseling, treatment, and sequelae. A societal-perspective analysis added patient productivity losses to the health care system costs. A payer-perspective analysis included direct medical costs for index patients, EPT, and partner visits and sequelae only to the extent that partners would seek clinical care paid by the same payer. The payer-perspective analysis was included to assess the impact of EPT compared with SR from the perspective of an individual organization, such as a health insurer or county or state health department.
The time frame of the cost analysis was bounded by the follow-up times in the studies: 3 to 19 weeks in Seattle-King County and 4 to 8 weeks in New Orleans. The analytic horizon included lags of up to 10 years for sequelae of PID, although for the payer-perspective analysis, we used an analytic horizon of 5 years.12,14 Because patients change insurers frequently, care for sequelae developing with a large time delay may not be directly paid by the insurer at the time of the initial chlamydial or gonococcal infection. Cases of PID were converted to quality-adjusted life-years (QALYs) lost using previously published health utility index values.22,23 We did not assess any QALY loss due to acute chlamydial infection.
We conducted Monte Carlo simulations (10,000 iterations) in which the variables used in the analysis were simultaneously varied over ranges. Monte Carlo simulations allow the simultaneous varying of all uncertain variables in a model.24 We used a uniform distribution for the proportion of partners receiving care from the same payer. All other variables were assumed to follow a triangular distribution, which can be characterized with only a maximum, minimum, and median.25 We also conducted univariate sensitivity analyses, including an analysis in which we set the proportion of index patients infected at follow-up equal to each other for Seattle at 0.12, the combined average rate for EPT and SR for index patients initially diagnosed with chlamydia. We further used Seattle data to examine the cost difference between EPT and SR under varying assumptions about how EPT might be implemented. First, data entry costs were eliminated for both EPT and SR, and counseling costs were eliminated from SR. This analysis depicted 2 systems for comparison. First, it depicted a system in which public health staff provides EPT to persons with gonorrhea and chlamydia. Second, it depicted a system that maintains case report information but provides no public health partner services. Second, all counseling and data entry costs were eliminated for both EPT and SR. This depicted a partner notification system in which providers use EPT but do not elicit information about partners or counsel patients beyond that typically done following an STD diagnosis. In this analysis, we assumed health departments would not perform partner notification for partners of patients with gonorrhea or chlamydia. Data were analyzed using Stata 11.0 (StataCorp LP, College Station, TX) and Excel 2007 (Microsoft Corporation, Redmond, WA).
The variables used in the analysis are shown in Table 1. The staff time spent per patient did not significantly vary between the standard referral and expedited partner therapy arms at either site (P < 0.05). The costs, partners treated, and QALYs lost in index patients and their partners are shown in Table 2. At baseline, EPT was more effective in treating partners, resulted in the loss of fewer QALYs, and was lower in cost than SR (whether considering health care system costs or societal costs); therefore, EPT was cost saving. The Monte Carlo simulation varied all variables over the ranges in Table 1 and calculated the cost per index patient for SR and EPT. EPT was less costly from a health care system perspective than SR in all but an average of 3 per 10,000 simulations or fewer when considering Seattle data (for men or women), and an average of 144 per 10,000 simulations when using New Orleans-specific data over 10 iterations.
To compare the cost per index patient of SR and EPT from the perspective of an individual payer, we included a variable to control for the proportion of partners of the index patient whose costs for medical care would be paid by the same payer as that of the index patient. A Monte Carlo simulation including this variable yielded the costs per index patient shown in Figures 1A (Seattle) and B (New Orleans). The horizontal axis of each graph indicates the proportion of partners whose costs for care would be paid by the same payer as that of the index patient. The vertical axis indicates the cost per index patient of EPT minus SR: a negative value indicates that EPT would cost the payer less per index patient than SR. Trend lines are shown on each figure. The point at which the trend lines in each figure cross the horizontal axis shows the proportion of partners at which the costs of EPT and SR are equal—these are 0.32 and 0.37 for female partners of index men (Seattle and New Orleans, respectively) and 0.29 for male partners of index women (Seattle).
In Table 2, we assumed that 25% of partners receiving EPT also sought medical evaluation (clinical care). Changing the distribution of the variable for the proportion of partners of the index patients receiving EPT who would also seek clinical care to a baseline of 0.50 (range, 0.25–0.75) yielded Monte Carlo results qualitatively similar to those in Figures 1A and 1B, with the exception that the threshold values for cost equivalence changed to 0.48 (from 0.32) and 0.54 (from 0.37) for female partners of index men (Seattle and New Orleans, respectively) and 0.52 (from 0.29) for male partners of index women (Seattle). When the partner care-seeking proportion was lowered to a mean of 0.10 (range, 0.0–0.25), the threshold values for cost equivalence changed to 0.28 (from 0.32) and 0.32 (from 0.37) for female partners of index men (Seattle and New Orleans, respectively) and 0.23 (from 0.29) for male partners of index women (Seattle).
A Monte Carlo simulation was also used to compare the payer-perspective costs “per partner treated” (rather than “per index patient”) of EPT and SR. This is a different analysis than the cost per index patient because the number of partners treated by EPT is greater than the number of partners treated by SR. The cost per partner could be lower with EPT than with SR even though the cost per index patient might be higher with EPT than with SR, because more partners are treated with EPT than with SR. The payer-perspective cost per partner treated using EPT or SR was equal when the proportion of partners of index men receiving care funded by the same payer as the index man was 0.03 and 0.07 (Seattle and New Orleans, respectively). At higher proportions of partners receiving care funded by the same payer as the index, EPT was less costly per partner than SR. For index women, the payer-perspective cost per partner treated was lower using EPT than when using SR, regardless of what proportion of men received care from the same provider (Seattle).
In univariate sensitivity analysis, EPT treated more partners than SR across the entire ranges of the proportions of partners treated for EPT and SR. However, even if the proportion of partners treated for EPT was set equal to those treated for SR, EPT was less costly using either a health care system or societal perspective, meaning that EPT was still cost saving even when it was not more effective in terms of the number of partners treated. In terms of cost per index patient, EPT was less costly than SR unless the proportion of partners receiving EPT who also sought clinical care exceeded 0.66 from a health care system perspective or 0.82 from a societal perspective using Seattle data. When we set the infection rates at follow-up for EPT and SR equal to each other, EPT remained cost saving from the health care system and societal perspectives.
We conducted additional sensitivity analyses using Seattle data to estimate the cost-effectiveness of EPT in different health care systems. First, we eliminated data entry costs for EPT and SR, and also eliminated costs associated with contacting and counseling persons receiving SR. These assumptions simulated a system in which a health department maintains a case reporting system but provides no partner services to a system which provides partner services that include EPT. Under these assumptions, EPT was less costly than SR from the health care system and societal perspectives for both index men and index women. Overall health care system costs for EPT compared with SR were 10% lower for index men and 8% lower for index women. Societal costs for EPT compared with SR were 17% lower for index men and 26% lower for index women. Considering only payer-perspective costs, the magnitude of the cost difference would depend on the proportion of partners receiving care from the same payer. However, the incremental cost of EPT was less than $13,000 per QALY saved for index women over SR, regardless of what percentage of partners sought care from the same payer. We then eliminated counseling and data entry costs for both EPT and SR to assess the cost effectiveness of a system in which medical providers use EPT with minimal counseling. This made EPT less costly than SR from all perspectives, ranging from 15% lower from the health care system perspective for index men to 36% lower from the societal perspective for index women. From the payer perspective, EPT cost less than $8000 per QALY gained over SR (the exact magnitude varied depending on the percentage of partners seeking care from the same payer.
EPT is cost effective under a wide range of assumptions, however, the magnitude of the cost-effectiveness is dependent on analysis perspective. From the health care system- or societal-perspective, EPT was cost saving: it resulted in more partners treated at lower cost than SR. In contrast, EPT was not cost saving in all sensitivity analyses for individual payers. When EPT was not cost saving compared with SR from the individual payer perspective, the incremental cost per QALY gained through EPT compared with SR was less than $13,000, a cost per QALY that is typically considered to be very cost effective.26,27 A payer such as a state Medicaid program would realize a direct cost saving only if a substantial proportion of an index patient's partners would seek care through the same payer (at least 29%, in the case of female index patients, when assuming that 25% of partners treated through EPT would also seek clinical care; Fig. 1A). The payer-perspective cost advantage of SR relative to EPT was greatly reduced or eliminated in the sensitivity analysis that was designed to depict the circumstances under which EPT might be implemented in most settings: where the payer would not incur costs for data entry for either SR or EPT, and would only incur costs for patient counseling for EPT.
However, even with reduced costs for implementation of EPT, the relative costs of EPT and SR will depend on patient and partner patterns that can vary. EPT is always more cost effective from a health care system and societal perspective than from the perspective of an individual payer. This disparity between societal and individual payer perspectives illustrates how the fragmentation of health care financing in the United States creates a situation in which decision-making by individual organizations to minimize their own costs can increase costs for the health care system and for society as a whole. Economists describe this as an externality; the cost individual payers incur for EPT do not fully reflect the benefits it delivers; therefore, individual payers may underuse the intervention. Another intervention that has beneficial externalities is vaccination. In instances with beneficial externalities, subsidies are often used to encourage optimal allocation of the resource creating the benefit.28
Recently enacted health care legislation may change the calculus related to EPT for large insurers like Medicaid due to changes in enrollment. This could lead to large payers finding EPT to be cost-minimizing for their own programs, because as they gain market share, the proportion of their enrollees' partners who have the same insurer could also increase. Even if EPT is not less costly to Medicaid programs, our findings indicate that increasing the usage of EPT is still optimal because under most circumstances it will be lowest cost to the health care system and will increase QALYs over SR. Its adoption can be encouraged through subsidies or regulation.
Our analysis is limited by our exclusion of the potential population-level transmission effects of the intervention. Optimally, population-level effects would be included in a consideration of cost effectiveness. Transmission modeling would require additional data on sex partners.29 Preliminary transmission modeling has suggested that EPT could have a substantial impact on population prevalence of chlamydia if widely implemented.30 To date, chlamydia transmission models have yielded greatly differing predictions about the population-level impact of interventions; therefore, it is uncertain whether incorporating transmission effects in this analysis would improve or reduce its validity.31 Although these results do not capture all of the potential effects of EPT, they provide useful information for policy makers assessing whether to adopt EPT. Another limitation is that individual payers might incur different costs than we assessed for clinical services, leading to different payer-perspective results.
When considering intervention cost, repeat visits by index patients, and the cost of sequelae, EPT is less costly and improves partner treatment compared with SR. These findings should prompt health departments, insurers, and policy makers to develop approaches to ensure that EPT is widely available.
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