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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