Prediction Model to Maximize Impact of Syphilis Partner Notification—San Francisco, 2004–2008

Unnamed Partners From Syphilis Partner Services Interviews, 7 Jurisdictions

BACKGROUND

Reducing transmission depends on the percentage of infected partners treated; if many are missed, impact on transmission will be low. Traditional partner services metrics evaluate the number of partners found and treated. We estimated the proportion of partners of syphilis patients not locatable for intervention.

METHODS

We reviewed records of early syphilis cases (primary, secondary, early latent) reported in 2015 to 2017 in 7 jurisdictions (Florida, Louisiana, Michigan, North Carolina, Virginia, New York City, and San Francisco). Among interviewed syphilis patients, we determined the proportion who reported named partners (with locating information), reported unnamed partners (no locating information), and did not report partners. For patients with no reported partners, we estimated their range of unreported partners to be between one and the average number of partners for patients who reported partners.

RESULTS

Among 29,719 syphilis patients, 23,613 (80%) were interviewed and 18,581 (63%) reported 84,224 sex partners (average, 4.5; 20,853 [25%] named and 63,371 [75%] unnamed). An estimated 11,138 to 54,521 partners were unreported. Thus, 74,509 to 117,892 (of 95,362-138,745) partners were not reached by partner services (78%-85%). Among interviewed patients, 71% reported ≥1 unnamed partner or reported no partners; this proportion was higher for men who reported sex with men (75%) compared with men who reported sex with women only (65%) and women (44%).

CONCLUSIONS

Approximately 80% of sex partners were either unnamed or unreported. Partner services may be less successful at interrupting transmission in networks for men who reported sex with men where a higher proportion of partners are unnamed or unreported.

Integrating Human Immunodeficiency Virus Testing Into Syphilis Partner Services in Mississippi to Improve Human Immunodeficiency Virus Case Finding

BACKGROUND

Mississippi has the 10th highest rate of new human immunodeficiency virus (HIV) infections in the United States. The Mississippi State Department of Health (MSDH) integrated partner HIV testing into syphilis partner services (PS) in 2014, but the effectiveness of this as an HIV case finding strategy has not been evaluated.

METHODS

We identified all early syphilis (primary, secondary, and early latent) case records reported from July 1, 2014, to December 31, 2016, excluding case records for people concurrently newly diagnosed with HIV. Among sex partners of these people, we identified new diagnoses of early syphilis and HIV. We calculated the number needed to interview as the number of syphilis index case patients interviewed divided by the number of partners newly diagnosed with early syphilis or HIV.

RESULTS

A total of 1535 (95%) of the 1619 early syphilis index case patients were interviewed for PS. These case patients named 2267 partners, of whom 1868 (82%) were contacted by MSDH. Among partners, 1508 (81%) tested for syphilis and 745 (56%) of 1321 partners not previously diagnosed with HIV were tested for HIV. Partner services identified 696 new early syphilis case patients (46%) and 24 (3.2%) new HIV case patients among partners. Sixty-four index case patient interviews were needed to identify 1 new case of HIV, and 2 interviews were needed to identify 1 new case of syphilis among partners.

CONCLUSIONS

Syphilis PS allowed MSDH to interact with 1592 men who have sex with men over a 30-month period and was effective for identifying people newly infected with early syphilis and HIV. Increasing HIV testing among partners of syphilis case patients could increase HIV case finding in Mississippi.

Frequency and Characteristics of Biological False-Positive Test Results for Syphilis Reported in Florida and New York City, USA, 2013 to 2017

Discordant syphilis test results, with a reactive nontreponemal test and nonreactive treponemal test are usually considered biological false-positive test results (BFPs), which can be attributed to other conditions. Syphilis surveillance laws mandate laboratory reporting of reactive syphilis tests, which include many BFPs. We describe the frequency of BFPs, titer distributions, and titer increases from reported test results in Florida and New York City (NYC). Reactive nontreponemal tests for individuals with at least one nonreactive treponemal test and no reactive treponemal test were extracted from sexually transmitted disease (STD) surveillance systems in Florida and NYC from 2013 to 2017. Characteristics of individuals with BFPs were analyzed after selecting the observation with the highest titer from each individual. We next considered all results from individuals to characterize persons who had a 4-fold titer increase between successive nontreponemal tests. Among 526,540 reactive nontreponemal tests, there were 57,580 BFPs (11%) from 39,920 individuals. Over 90% (n = 52,330) of BFPs were low titer (≤1:4), but 654 (1%) were high-titer BFPs (≥1:32). Very high-titer (≥1:128) BFPs were more common among individuals over 60 years of age (odds ratio [OR], 2.68; 95% confidence interval [CI], 1.22 to 5.91). A 4-fold increase in titer was observed among 1,863 (14%) individuals with more than one reported BFP. Most BFPs detected by surveillance were low titer, but some were high titer and some had a 4-fold increase in titer. Review of patient histories might identify underlying conditions contributing to these high and rising titers.

The Number of Interviews Needed to Yield New Syphilis and Human Immunodeficiency Virus Cases Among Partners of People Diagnosed With Syphilis, North Carolina, 2015

Compare syphilis investigation yield among patient groups using number needed to interview.

GOAL

To increase investigation efficiency.

STUDY DESIGN

Retrospective review of North Carolina 2015 syphilis investigations, using the number of cases needed to interview (NNTI) and the total number of cases and contacts needed to interview (TNTI) to compare yield of new syphilis and human immunodeficiency virus diagnoses between patient groups.

RESULTS

We reviewed 1646 early syphilis cases and 2181 contacts; these yielded 241 new syphilis cases (NNTI, 6.9; TNTI, 16.4) and 38 new human immunodeficiency virus cases (NNTI, 43). Interviews of women (prevalence difference [PD] = 6%, 95% confidence interval [CI], 12-16), patients <30 years old (PD = 5%, 95% CI, 1-8), and patients with titer >1:16 (PD = 5%, 95% CI, 1-9) yielded more new syphilis cases in our adjusted model; no other patient factors increased investigation yield.

CONCLUSIONS

The NNTI and TNTI are useful measures of efficiency. Prioritizing early syphilis investigation by gender, rapid plasmin reagin titer, and age provides small increases in efficiency; no other factors increased efficiency.

Adaptation of the HIV Care Continuum as a Method for Evaluating Syphilis and Gonorrhea Disease Control Activities in Los Angeles County

BACKGROUND

Treatment verification and contact elicitation are core approaches used to control the spread of sexually transmitted diseases (STDs). Methodology adapted from the HIV care continuum is presented as an evaluation and communication tool for STD control activities.

METHODS

Sexually transmitted disease surveillance and program data for Los Angeles County in 2013 were used to construct a 2-part continuum to examine syphilis (all stages) and gonorrhea outcomes among index patients and elicited contacts. The Index Case Continuum (Part 1) assesses the proportion of patients who were treated, assigned for interview, interviewed, and provided name and locating information for at least 1 contact. The Elicited Contact Continuum (Part 2) assesses the proportion of contacts who were located, interviewed, and treated.

RESULTS

Among 3668 patients with syphilis, 97% (n = 3556) were treated, 72% (n = 2633) were interviewed, and 25% (n = 920) provided name and locating information for at least 1 contact. The corresponding numbers for 12,541 gonorrhea cases were 95% (n = 11,936), 45% (n = 5633), and 16% (1944), respectively. Among the 1392 contacts elicited from syphilis cases, 53% (n = 735) were either interviewed or determined to not need an interview and 43% (n = 595) were treated. The corresponding numbers for the 2323 contacts elicited from gonorrhea cases were 53% (n = 1221) and 46% (n = 1075), respectively.

CONCLUSIONS

Adaptation of the HIV continuum is a useful tool for evaluating treatment verification and contact elicitation activities. In Los Angeles County, this approach revealed significant drop-offs in the proportion of index cases naming contacts and in the proportion of contacts who are interviewed and treated.

Public health interventions to control syphilis

Syphilis control strategies are old, but interventions have changed and there is now a more scientific approach to evidence of effectiveness. We searched PubMed using 'syphilis control' to identify papers that measured the effectiveness of interventions. We also included novel approaches and comprehensive responses to outbreaks. Few papers used high-quality research methodology and fewer evaluated impact on prevalence or incidence; most assessed intermediate outcomes. Syphilis can often be controlled by a combination of case finding, treatment and education. However, outbreaks are unique and ongoing evaluation is needed to see if interventions are producing intended intermediate outcomes at reasonable costs.

Towards probabilistic decision support in public health practice: predicting recent transmission of tuberculosis from patient attributes

OBJECTIVE

Investigating the contacts of a newly diagnosed tuberculosis (TB) case to prevent TB transmission is a core public health activity. In the context of limited resources, it is often necessary to prioritize investigation when multiple cases are reported. Public health personnel currently prioritize contact investigation intuitively based on past experience. Decision-support software using patient attributes to predict the probability of a TB case being involved in recent transmission could aid in this prioritization, but a prediction model is needed to drive such software.

METHODS

We developed a logistic regression model using the clinical and demographic information of TB cases reported to Montreal Public Health between 1997 and 2007. The reference standard for transmission was DNA fingerprint analysis. We measured the predictive performance, in terms of sensitivity, specificity, negative predictive value, positive predictive value, the Receiver Operating Characteristic (ROC) curve and the Area Under the ROC (AUC).

RESULTS

Among 1552 TB cases enrolled in the study, 314 (20.2%) were involved in recent transmission. The AUC of the model was 0.65 (95% confidence interval: 0.61-0.68), which is significantly better than random prediction. The maximized values of sensitivity and specificity on the ROC were 0.53 and 0.67, respectively.

CONCLUSIONS

The characteristics of a TB patient reported to public health can be used to predict whether the newly diagnosed case is associated with recent transmission as opposed to reactivation of latent infection.

Risk prediction in sexual health contexts: protocol

BACKGROUND

In British Columbia (BC), we are developing Get Checked Online (GCO), an Internet-based testing program that provides Web-based access to sexually transmitted infections (STI) testing. Much is still unknown about how to implement risk assessment and recommend tests in Web-based settings. Prediction tools have been shown to successfully increase efficiency and cost-effectiveness of STI case finding in the following settings.

OBJECTIVE

This project was designed with three main objectives: (1) to derive a risk prediction rule for screening chlamydia and gonorrhea among clients attending two public sexual health clinics between 2000 and 2006 in Vancouver, BC, (2) to assess the temporal generalizability of the prediction rule among more recent visits in the Vancouver clinics (2007-2012), and (3) to assess the geographical generalizability of the rule in seven additional clinics in BC.

METHODS

This study is a population-based, cross-sectional analysis of electronic records of visits collected at nine publicly funded STI clinics in BC between 2000 and 2012. We will derive a risk score from the multivariate logistic regression of clinic visit data between 2000 and 2006 at two clinics in Vancouver using newly diagnosed chlamydia and gonorrhea infections as the outcome. The area under the receiver operating characteristic curve (AUC) and the Hosmer-Lemeshow statistic will examine the model's discrimination and calibration, respectively. We will also examine the sensitivity and proportion of patients that would need to be screened at different cutoffs of the risk score. Temporal and geographical validation will be assessed using patient visit data from more recent visits (2007-2012) at the Vancouver clinics and at clinics in the rest of BC, respectively. Statistical analyses will be performed using SAS, version 9.3.

RESULTS

This is an ongoing research project with initial results expected in 2014.

CONCLUSIONS

The results from this research will have important implications for scaling up of Internet-based testing in BC. If a prediction rule with good calibration, discrimination, and high sensitivity to detect infection is found during this project, the prediction rule could be programmed into GCO so that the program offers individualized testing recommendations to clients. Further, the prediction rule could be adapted into educational materials to inform other Web-based content by creating awareness about STI risk factors, which may stimulate health care seeking behavior among individuals accessing the website.