In Washington State, STD PS interviews are primarily conducted over the telephone, integrate expedited partner therapy (EPT) for heterosexuals with gonorrhea or chlamydia(17), and promote HIV-specific interventions for MSM and transgender persons with an STD diagnosis or exposure. HIV interventions include HIV testing(7, 18), linkage to treatment(19), and linkage to PrEP for high-risk individuals(20). PS are provided to all cases of early syphilis and select cases of gonorrhea/chlamydia, including all pregnant women and persons with untreated infections, and in some cases, MSM, transgender persons, and adolescents depending on case risk factors and resource availability. Field visits were conducted on priority cases, only when efforts to reach the individual via several telephone and text attempts, emails, and letters had failed. Spokane also utilized Facebook messenger to make contact and conducted field visits when individuals with syphilis were incarcerated at the nearby local jail. King only provided field visits to untreated cases.

This study estimates the costs for STD PS delivery from the perspective of the health department at three local health jurisdictions: Public Health – Seattle & King County (King), Tacoma-Pierce County Health Department (Pierce), Spokane Regional Health District (Spokane). These high-burden locations were selected to represent the diversity within the State. King serves the dense urban city of Seattle and the surrounding area, Pierce serves the city of Tacoma and the more rural surrounding area in the county directly south of King, and Spokane serves the less dense city of Spokane and the rural surrounding area in the eastern most part of the State. For each location, we present the population size reported by the U.S. census bureau and the number of reported STD cases by risk characteristic (MSM, men who have sex with women (MSW), men with unknown risk, and women) using county-level disease surveillance data from 2016. We conducted a micro-costing analysis in 2016-2017 to estimate staff time allocation for specific components of PS delivery and estimated the total time personnel allocated to STD PS. Analyses included a time study and financial expenditure assessment. We used surveillance and programmatic data to estimate health service delivery indicators, outcomes, and associated costs. Results are stratified by jurisdiction to investigate heterogeneity in disease burden, population characteristics, costs, and program models.

These activities were conducted as part of public health program evaluation and therefore not considered human subjects research. Analyses were conducted using Microsoft Excel 2017 and Stata/SE 14.2.

We used county-level surveillance and PS data from 2016 to determine all health services indicators unless otherwise stated, including the total numbers of STD cases diagnosed, assigned for PS, and interviewed by DIS, and the numbers of partners named by OPs, notified by DIS or OP, tested, diagnosed, and treated following the OP’s PS interview. We also determined the number of OPs provided with EPT, and HIV-negative clients (OPs and partners) tested for HIV and referred to PrEP through PS, referred to as enhanced PS outcomes. Information for PrEP referrals was collected empirically for OPs in King County and via DIS self-report for STD PS clients combined (OPs and partners) in Pierce and Spokane, so are not directly comparable. The number of HIV-infected OPs identified as inadequately engaged in HIV care (defined as not being on antiretroviral therapy or, if treatment status is unknown, reporting having no provider or visit in the prior 6 months/scheduled future visit at the time of interview) and the number linked to care following PS (virally suppressed 6 months following interview) were estimated when available. Partner outcome indices were calculated by dividing the total number of partners with each outcome (number notified, tested, treated, etc.) by the number of OPs interviewed(21). Cases with multiple STDs (coinfections) were included as the higher priority STD in the following order: syphilis, gonorrhea, chlamydia.

We conducted a time study of all DIS and other PS staff. First, an independent observer assessed how much time each staff member spent on each activity over several hours during a typical workday. To complement this information, each staff member was interviewed prior to the observations (and after if observations revealed omissions) to gain a more complete understanding of workflow, time allocation, and if they had unrelated job responsibilities; these data were used to estimate the proportion of administrative staff and DIS labor allocated to STD PS based on their self-report and confirmed by the supervisor. Second, PS staff conducted individual case tracking and reported specific activities from case report, assignment, through to case closure. Tracked cases were purposively sampled to include cases representing a variety of STDs and risk characteristics.

We estimated total personnel hours spent per week on key activities by STD. We also summarized tracking form data to present the means, medians, and variability in time spent per case by STD and population. The total time allocated per case was estimated by dividing the average weekly number of hours allocated for work related to STD PS by the average number of cases assigned to STD PS in a week (calculated by dividing the total number of cases worked in 2016 by 44 work weeks, the average number of weeks worked by staff in a year).

2016 financial records for personnel salaries and benefits and overhead were adjusted based on the percentage of time staff allocated to STD PS to estimate the total STD PS program costs by STD type at each jurisdiction. Benefit costs were provided by the PS supervisor for each staff member and overhead costs were calculated as a percent of salaries, defined as the amount charged against labor in each county (33% in King and 30% in Pierce and Spokane). Activities and time unrelated to STD PS were excluded from analyses. The total costs per STD PS outcomes (e.g. OP interview, partner notified, tested and treated after DIS interview, etc.) were calculated by dividing the estimated total program cost by the number of individuals known to have received that service or have that outcome in 2016. Outcomes achieved per $100,000 invested in STD PS were calculated by dividing the number of individuals known to have received that service by total program cost and multiplying by $100,000. All costs were adjusted for inflation to 2016 US dollars.

At all three jurisdictions, administrative/data entry staff process laboratory and case reports for all gonorrhea/chlamydia cases. Once the initial case report is entered into the statewide web-based STD surveillance/PS database, cases are assigned to DIS for PS depending on STD, risk criteria, and available resources (Figure 1). For new syphilis cases, State Department of Health (DOH) staff assign possible cases to DIS for review and PS.

Observations were conducted on select days in 2016-2017 in each health department. Pre-assignment administrative and data entry work for gonorrhea/chlamydia was conducted by three staff members in King and one each in Pierce and Spokane. There were 7, 5, and 4 DIS working on STD PS in King, Pierce, and Spokane, respectively (see supplement for additional details on staff time).

In King, Pierce, and Spokane, respectively, DIS combined spent an average total of 73, 17, and 73 hours per week on syphilis PS overall; worked an average of 11, 3, and 3 cases per week; and allocated an average of 6.5, 6.4, and 28.8 hours per case (Figure 2). DIS combined spent an average total of 142, 88, and 27 hours per week on gonorrhea/chlamydia PS work overall; worked an average of 96, 55, and 9 cases per week; and allocated an average of 1.5, 1.6, and 2.9 hours per case, respectively.

Estimated aggregate time in hours and percent of time spent per week on PS activities varied across STD and jurisdiction, but some trends were observed (Supplemental Figure 1 and Supplemental Table 1). Administrative staff’s work was similar for all reported gonorrhea/chlamydia cases regardless of whether the case met criteria for PS follow-up and DIS investigation, spending the majority of their time on data entry at all jurisdictions (>53%). King administrative staff and DIS spent the largest percentage of time (17% and 9%, respectively) contacting healthcare providers to obtain and complete case reports vs. Pierce and Spokane (<3%). For syphilis STD PS, DIS spent a similar share of time contacting healthcare providers in King (22%) and Pierce (19%) vs. less time in Spokane (3%). Spokane staff directly accessed electronic medical records (EMR) and could look up case information directly.

For syphilis, DIS spent 6%, 31%, and 11% of time conducting case interviews and partner notification vs. 21%, 39%, and 16% of gonorrhea/chlamydia work-time in King, Pierce, and Spokane, respectively. DIS in Spokane spent a greater proportion of time conducting field work for gonorrhea/chlamydia (18% vs. <6% in King and Pierce) and reported interviews were often conducted at the nearby county detention center. DIS working on gonorrhea/chlamydia in Spokane and Pierce spent a greater percent of time using electronic resources (e.g. EMRs and Facebook) to locate and contact OPs and partners than in King. Facebook was generally used after other methods (e.g. phone calls, texting) were unsuccessful. Only DIS in Spokane frequently used local police blotters. In all jurisdictions, not all staff had access to commonly used electronic data sources (e.g. Accurint® or the state syphilis serology database), resulting in interruptions to staff with access to obtain information.

Time spent directly on casework captured by individual case tracking varied substantially across cases (Supplemental Table 2). More DIS time was spent on syphilis than gonorrhea/chlamydia casework across jurisdictions. Among cases with substance use information, casework for methamphetamine users took longer than non-users for Spokane syphilis cases (limited data regarding methamphetamine use was available from tracked cases in King and Pierce). While complicated high-priority cases like neurological and neonatal syphilis are rare, DIS spent a much larger amount of time conducting related casework, resulting in extreme outliers for time spent per case.

STD PS objectives such as EPT, HIV testing, linkage and re-linkage to HIV care, and PrEP referrals took minimal time relative to overall work (30 seconds to 2 min per topic per interview), except for PrEP referrals in Pierce. Clients often already had a documented HIV test, were not HIV-positive, or were already linked to care and on antiretroviral treatment if they were HIV-positive, minimizing additional DIS interventions. Some PrEP eligible clients had already discussed PrEP with their healthcare provider. King and Spokane had public health PrEP coordinators so DIS typically took only a few minutes to assess client eligibility and interest in PrEP and then referred the client to the coordinator. However, DIS in Pierce coordinated PrEP referrals and initiations themselves, including counseling and collecting blood samples for PrEP eligibility required for initiation, which DIS reported took approximately 69-155 minutes per referral for 3-6 clients per week.

King has the largest population and most reported STD diagnoses (Table 1). Pierce had approximately twice the number of reported gonorrhea/chlamydia cases than Spokane, but a similar number of syphilis cases. The majority (>80%) of syphilis cases in King and Pierce were identified as MSM vs. 38% in Spokane. For gonorrhea, about half (52%) of cases in King were identified as MSM vs. <20% in Pierce and Spokane.

Nearly all (>96%) of reported syphilis cases, 66%-95% of reported gonorrhea cases, and a minority of chlamydia cases were assigned to PS across the jurisdictions (Table 2). Approximately 270, 268, and 61 syphilis and 1,177, 1,105, and 769 gonorrhea/chlamydia cases were assigned for PS per full-time DIS, in King, Pierce and Spokane, respectively. Of reported syphilis cases, 70%-91% were successfully interviewed by DIS and 35%-70% of reported gonorrhea cases were successfully interviewed (Table 3a). Partner outcome indices were lowest in King for syphilis cases and relatively similar across jurisdictions for gonorrhea/chlamydia. In 2016, median time from lab diagnosis to DIS interview in King, Pierce and Spokane, respectively, for syphilis was 13 days (IQR 6-32), 5 (1-12), and 5 (0-13), and for gonorrhea/chlamydia was 8 (3-18), 4 (0-10), and 8 (4-20).

We estimated that the annual costs for STD PS were $798,141, $416,098, and $400,759 in King, Pierce, and Spokane, respectively (Table 2). At the time of observations, syphilis-related work accounted for an estimated 28%, 15%, and 57% of total STD PS resources, respectively. Spokane was uniquely supported by an on-site DOH-funded syphilis consultant (costs were included in estimate as the consultant’s contributions were necessary for service delivery to address the epidemic at this location). The incremental costs of PS activities can be derived by multiplying the program costs (Table 2) by the percent of personnel-time spent on activities (Supplemental Table 1).

The estimated total costs per OP interview were lowest in Pierce and highest in Spokane for all STDs, and higher for syphilis vs. gonorrhea/chlamydia (Table 3a). The total cost per HIV test of all STD PS clients combined following the DIS interview ranged from $988-$5,467 (Table 3b), per client newly diagnosed with HIV was >$130,000 for all jurisdictions, per OP identified as HIV infected and inadequately engaged in care ranged from $10,203-$111,837, and per HIV-uninfected client accepting a PrEP referral ranged from $2,551-$57,467. Outcomes achieved per $100,000 invested in STD PS varied substantially by jurisdiction (Table 3c). For syphilis and gonorrhea, more outcomes were achieved in Pierce per $100,000 invested than in King and Spokane.