Deriving and validating a risk estimation tool for screening asymptomatic chlamydia and gonorrhea

Identifying Individuals at High Risk for HIV and Sexually Transmitted Infections With an Artificial Intelligence-Based Risk Assessment Tool

Background

We have previously developed an artificial intelligence-based risk assessment tool to identify the individual risk of HIV and sexually transmitted infections (STIs) in a sexual health clinical setting. Based on this tool, this study aims to determine the optimal risk score thresholds to identify individuals at high risk for HIV/STIs.

Methods

Using 2008-2022 data from 216 252 HIV, 227 995 syphilis, 262 599 gonorrhea, and 320 355 chlamydia consultations at a sexual health center, we applied MySTIRisk machine learning models to estimate infection risk scores. Optimal cutoffs for determining high-risk individuals were determined using Youden's index.

Results

The HIV risk score cutoff for high risk was 0.56, with 86.0% sensitivity (95% CI, 82.9%-88.7%) and 65.6% specificity (95% CI, 65.4%-65.8%). Thirty-five percent of participants were classified as high risk, which accounted for 86% of HIV cases. The corresponding cutoffs were 0.49 for syphilis (sensitivity, 77.6%; 95% CI, 76.2%-78.9%; specificity, 78.1%; 95% CI, 77.9%-78.3%), 0.52 for gonorrhea (sensitivity, 78.3%; 95% CI, 77.6%-78.9%; specificity, 71.9%; 95% CI, 71.7%-72.0%), and 0.47 for chlamydia (sensitivity, 68.8%; 95% CI, 68.3%-69.4%; specificity, 63.7%; 95% CI, 63.5%-63.8%). High-risk groups identified using these thresholds accounted for 78% of syphilis, 78% of gonorrhea, and 69% of chlamydia cases. The odds of positivity were significantly higher in the high-risk group than otherwise across all infections: 11.4 (95% CI, 9.3-14.8) times for HIV, 12.3 (95% CI, 11.4-13.3) for syphilis, 9.2 (95% CI, 8.8-9.6) for gonorrhea, and 3.9 (95% CI, 3.8-4.0) for chlamydia.

Conclusions

Risk scores generated by the AI-based risk assessment tool MySTIRisk, together with Youden's index, are effective in determining high-risk subgroups for HIV/STIs. The thresholds can aid targeted HIV/STI screening and prevention.

The Problem of Pain in the United States: A Population-Based Characterization of Biopsychosocial Correlates of High Impact Chronic Pain Using the National Health Interview Survey

Over 20 million adults in the United States live with high impact chronic pain (HICP), or chronic pain that limits life or work activities for ≥3 months. It is critically important to differentiate people with HICP from those who sustain normal activities although experiencing chronic pain. Therefore, we aim to help clinicians and researchers identify those with HICP by: 1) developing models that identify factors associated with HICP using the 2016 national health interview survey (NHIS) and 2) evaluating the performances of those models overall and by sociodemographic subgroups (sex, age, and race/ethnicity). Our analysis included 32,980 respondents. We fitted logistic regression models with LASSO (a parametric model) and random forest (a nonparametric model) for predicting HICP using the whole sample. Both models performed well. The most important factors associated with HICP were those related to underlying ill-health (arthritis and rheumatism, hospitalizations, and emergency department visits) and poor psychological well-being. These factors can be used for identifying higher-risk sub-groups for screening for HICP. We will externally validate these findings in future work. We need future studies that longitudinally predict the initiation and maintenance of HICP, then use this information to prevent HICP and direct patients to optimal treatments. PERSPECTIVE: Our study developed models to identify factors associated with high-impact chronic pain (HICP) using the 2016 National Health Interview Survey. There was homogeneity in the factors associated with HICP by gender, age, and race/ethnicity. Understanding these risk factors is crucial to support the identification of populations and individuals at highest risk for developing HICP and improve access to interventions that target these high-risk subgroups.

PSYCHOPATHY AND RISKY SEXUAL BEHAVIOR IN INCARCERATED WOMEN

To date, very few studies have explored the association between psychopathic traits and risky sexual behavior (RSB) among women. Here, we investigated this relationship in a sample of 137 incarcerated women. Psychopathic traits were assessed via the Hare Psychopathy Checklist-Revised (PCL-R) and lifetime RSB measures, including number of lifetime sexual partners, frequency of engaging in sexual intercourse while intoxicated, and frequency of forgoing protection (e.g., condom usage) during sexual intercourse, were assessed through self-report. PCL-R Facet 3 scores (assessing lifestyle psychopathic traits) were associated with an increased frequency of engaging in sexual intercourse while intoxicated. In addition, women scoring high on the PCL-R were more likely to engage in sexual intercourse while intoxicated compared with a previously collected sample of men scoring high on the PCL-R. The results obtained in the current study help improve our understanding of the association between psychopathic traits and RSB among women.

Screening for Chlamydia and Gonorrhea: US Preventive Services Task Force Recommendation Statement

IMPORTANCE

Chlamydia and gonorrhea are among the most common sexually transmitted infections in the US. Infection rates are highest among adolescents and young adults of both sexes. Chlamydial and gonococcal infections in women are usually asymptomatic and may lead to pelvic inflammatory disease and its associated complications. Newborns of pregnant persons with untreated infection may develop neonatal chlamydial pneumonia or gonococcal or chlamydial ophthalmia. Infection in men may lead to urethritis and epididymitis. Both types of infection can increase risk of acquiring or transmitting HIV.

OBJECTIVE

To update its 2014 recommendation, the US Preventive Services Task Force (USPSTF) commissioned a systematic review to evaluate the benefits and harms of screening for chlamydia and gonorrhea in sexually active adolescents and adults, including pregnant persons.

POPULATION

Asymptomatic, sexually active adolescents and adults, including pregnant persons.

EVIDENCE ASSESSMENT

The USPSTF concludes with moderate certainty that screening for chlamydia in all sexually active women 24 years or younger and in women 25 years or older who are at increased risk for infection has moderate net benefit. The USPSTF concludes with moderate certainty that screening for gonorrhea in all sexually active women 24 years or younger and in women 25 years or older who are at increased risk for infection has moderate net benefit. The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for chlamydia and gonorrhea in men.

RECOMMENDATION

The USPSTF recommends screening for chlamydia in all sexually active women 24 years or younger and in women 25 years or older who are at increased risk for infection. (B recommendation) The USPSTF recommends screening for gonorrhea in all sexually active women 24 years or younger and in women 25 years or older who are at increased risk for infection. (B recommendation) The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for chlamydia and gonorrhea in men. (I statement).

Screening for Chlamydial and Gonococcal Infections: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

The 2014 US Preventive Services Task Force (USPSTF) recommendation statement supported the effectiveness of screening for chlamydia and gonorrhea in asymptomatic, sexually active women 24 years or younger and in older women at increased risk for infection, although evidence for screening in men was insufficient.

OBJECTIVE

To update the 2014 USPSTF review on screening for chlamydial and gonococcal infection in adults and adolescents, including those who are pregnant.

DATA SOURCES

Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Ovid MEDLINE (January 1, 2014, through May 28, 2020) with surveillance through May 21, 2021.

STUDY SELECTION

Randomized clinical trials and observational studies of screening effectiveness, accuracy of risk stratification and alternative screening methods, accuracy of tests, and screening harms.

DATA EXTRACTION AND SYNTHESIS

One investigator abstracted data; a second checked accuracy. Two investigators independently assessed study quality.

MAIN OUTCOMES AND MEASURES

Complications of infection; infection transmission or acquisition; diagnostic accuracy of anatomical site-specific testing and collection methods; screening harms.

RESULTS

Twenty-seven studies were included (N = 179 515). Chlamydia screening compared with no screening was significantly associated with reduced risk of pelvic inflammatory disease (PID) in 2 of 4 trials and with reduced hospital-diagnosed PID (0.24% vs 0.38%); relative risk, 0.6 [95% CI, 0.4-1.0]), but not clinic-diagnosed PID or epididymitis, in the largest trial. In studies of risk prediction instruments in asymptomatic women, age younger than 22 years demonstrated comparable accuracy to extensive criteria. Sensitivity of chlamydial testing was similar at endocervical (89%-100%) and self- and clinician-collected vaginal (90%-100%) sites for women and at meatal (100%), urethral (99%), and rectal (92%) sites for men but lower at pharyngeal sites (69.2%) for men who have sex with men. Sensitivity of gonococcal testing was 89% or greater for all anatomical samples. False-positive and false-negative testing rates were low across anatomical sites and collection methods.

CONCLUSIONS AND RELEVANCE

Screening for chlamydial infection was significantly associated with a lower risk of PID in young women. Risk prediction criteria demonstrated limited accuracy beyond age. Testing for asymptomatic chlamydial and gonococcal infections was highly accurate at most anatomical sites, including urine and self-collected specimens. Effectiveness of screening in men and during pregnancy, optimal screening intervals, and adverse effects of screening require further evaluation.

Validation of a Clinical Prediction Rule to Predict Asymptomatic Chlamydia and Gonorrhea Infections Among Internet-Based Testers

BACKGROUND

Clinical prediction rules (CPRs) can be used in sexually transmitted infection (STI) testing environments to prioritize individuals at the highest risk of infection and optimize resource allocation. We previously derived a CPR to predict asymptomatic chlamydia and/or gonorrhea (CT/NG) infection among women and heterosexual men at in-person STI clinics based on 5 predictors. Population differences between clinic-based and Internet-based testers may limit the tool's application across settings. The primary objective of this study was to assess the validity, sensitivity, and overall performance of this CPR within an Internet-based testing environment (GetCheckedOnline.com).

METHODS

We analyzed GetCheckedOnline online risk assessment and laboratory data from October 2015 to June 2019. We compared the STI clinic population used for CPR derivation (data previously published) and the GetCheckedOnline validation population using χ2 tests. Calibration and discrimination were assessed using the Hosmer-Lemeshow goodness-of-fit test and the area under the receiver operating curve, respectively. Sensitivity and the fraction of total screening tests offered were quantified for CPR-predicted risk scores.

RESULTS

Asymptomatic CT/NG infection prevalence in the GetCheckedOnline population (n = 5478) was higher than in the STI clinic population (n = 10,437; 2.4% vs. 1.8%, P = 0.007). When applied to GetCheckedOnline, the CPR had reasonable calibration (Hosmer-Lemeshow, P = 0.90) and discrimination (area under the receiver operating characteristic, 0.64). By screening only individuals with total risk scores ≥4, we would detect 97% of infections and reduce screening by 14%.

CONCLUSIONS

The application of an existing CPR to detect asymptomatic CT/NG infection is valid within an Internet-based STI testing environment. Clinical prediction rules applied online can reduce unnecessary STI testing and optimize resource allocation within publicly funded health systems.

Performance of a tool to identify different types of self-reported sexual risk among women attending a contraception and sexual health clinic: results of a cross-sectional survey

INTRODUCTION

A clinical prediction rule (CPR) using psychosocial questions was previously derived to target sexual healthcare in general practice by identifying women at risk of unintended pregnancy (UIP) and sexually transmitted infections (STIs). This psychosocial CPR may help target resources within contraception and sexual health (CASH) services. This study investigated how well it predicted recent self-reported risk of UIP and STI acquisition among women attending a CASH clinic.

METHODS

Female patients aged 16-44 years attending a CASH clinic in South-East England were offered a questionnaire on arrival. This comprised psychosocial questions, and others addressing three sexual risks: (1) two or more male sexual partners in the last year (2+P), (2) risk of STI acquisition through most recent partner and (3) risk of UIP in the last 6 months. A CPR score was calculated for each participant and cross-tabulated against self-report of each sexual risk to estimate CPR sensitivity and specificity.

RESULTS

The psychosocial questions predicting 2+P had sensitivity 83.2% (95% CI 79.3% to 86.5%) and specificity 56.1% (95% CI 51.3%-60.6%). Those predicting combined 2+P and/or risk of STI acquisition through most recent partner had a sensitivity of 89.1% (95% CI 85.7%-91.8%) and specificity of 43.7% (95% CI 39.0%-48.5%). Questions predicting risk of UIP in the last 6 months had a sensitivity of 82.5% (95% CI 78.6%-86.0%) and specificity of 48.3% (95% CI 43.4%-53.1%).

CONCLUSIONS

The CPR demonstrated good sensitivity but low specificity, so may be suited to triaging or stratifying which interventions to offer CASH patients and by which mode (eg, online vs face-to-face). Further investigation of causal links between psychosocial factors and sexual risk is warranted to support development of psychosocial interventions for this patient group.

Cost-effectiveness of Sexually Transmitted Infection Screening for Adolescents and Young Adults in the Pediatric Emergency Department

IMPORTANCE

Adolescents and young adults compose almost 50% of all diagnosed sexually transmitted infection (STI) cases annually in the US. Given that these individuals frequently access health care through the emergency department (ED), the ED could be a strategic venue for examining the identification and treatment of STIs.

OBJECTIVE

To examine the cost-effectiveness of screening strategies for Chlamydia trachomatis and Neisseria gonorrhoeae (chlamydia and gonorrhea) in adolescents and young adults who seek acute care at pediatric EDs.

DESIGN, SETTING, AND PARTICIPANTS

This economic evaluation is a component of an ongoing, larger multicenter clinical trial at the Pediatric Emergency Care Applied Research Network. A decision analytic model, created using literature-based estimates for the key parameters, was developed to simulate the events and outcomes associated with 3 strategies for screening and testing chlamydial and gonococcal infections in individuals aged 15 to 21 years who sought acute care at pediatric EDs. Data sources included published (from January 1, 1997, to December 31, 2019) English-language articles indexed in MEDLINE, bibliographies in relevant articles, insurance claims data in the MarketScan database, and reimbursement payments from the Centers for Medicare and Medicaid Services. Because the events and outcomes were simulated, a hypothetical population of 10 000 ED visits by adolescents and young adults was used.

INTERVENTIONS

The 3 screening strategies were (1) no screening, (2) targeted screening, and (3) universally offered screening. Targeted screening involved the completion of a sexual health survey, which yielded an estimated STI risk (at risk, high risk, or low risk).

MAIN OUTCOMES AND MEASURES

Outcome metrics included cost (measured in 2019 US dollars) and the detection and successful treatment of STIs. The incremental cost-effectiveness ratio (ICER) of each strategy was calculated in a base case analysis. The ICER reflects the cost per case detected and successfully treated.

RESULTS

A 3.6% prevalence of chlamydia and gonorrhea was applied to a hypothetical population of 10 000 ED visits by adolescents and young adults. Targeted screening resulted in the detection and successful treatment of 95 of 360 STI cases (26.4%) at a cost of $313 063, and universally offered screening identified and treated 112 of 360 STI cases (31.1%) at a cost of $515 503. The ICER for targeted screening vs no screening was $6444, and the ICER for universally offered screening vs targeted screening was $12 139.

CONCLUSIONS AND RELEVANCE

This economic evaluation found that targeted screening and universally offered screening compared with no screening appeared to be cost-effective strategies for identifying and treating chlamydial and gonococcal infections in adolescents and young adults who used the ED for acute care. Universally offered screening was associated with detecting and successfully treating a higher proportion of STIs in this population.

Predicting the diagnosis of HIV and sexually transmitted infections among men who have sex with men using machine learning approaches

OBJECTIVES

We aimed to develop machine learning models and evaluate their performance in predicting HIV and sexually transmitted infections (STIs) diagnosis based on a cohort of Australian men who have sex with men (MSM).

METHODS

We collected clinical records of 21,273 Australian MSM during 2011-2017. We compared accuracies for predicting HIV and STIs (syphilis, gonorrhoea, chlamydia) diagnosis using four machine learning approaches against a multivariable logistic regression (MLR) model.

RESULTS

Machine learning approaches consistently outperformed MLR. Gradient boosting machine (GBM) achieved the highest area under the receiver operator characteristic curve for HIV (76.3%) and STIs (syphilis, 85.8%; gonorrhoea, 75.5%; chlamydia, 68.0%), followed by extreme gradient boosting (71.1%, 82.2%, 70.3%, 66.4%), random forest (72.0%, 81.9%, 67.2%, 64.3%), deep learning (75.8%, 81.0%, 67.5%, 65.4%) and MLR (69.8%, 80.1%, 67.2%, 63.2%). GBM models demonstrated the ten greatest predictors collectively explained 62.7-73.6% of variations in predicting HIV/STIs. STIs symptoms, past syphilis infection, age, time living in Australia, frequency of condom use with casual male sexual partners during receptive anal sex and the number of casual male sexual partners in the past 12 months were most commonly identified predictors.

CONCLUSIONS

Machine learning approaches are advantageous over multivariable logistic regression models in predicting HIV/STIs diagnosis.

Protecting our future generation: study protocol for a randomized controlled trial evaluating a sexual health self-care intervention with Native American youth and young adults

Background

Disparities in sexually transmitted infections (STI) are an urgent problem among Native American youth and young adults which are not fully explained by different sexual or related behaviors. These sexual health disparities are more likely attributed to social environments and structural determinants such as a shortage of sexual healthcare providers, lower socioeconomic status, and access barriers to STI screening and treatment, including geographic isolation and confidentiality concerns. Innovative, non-clinic based alternatives to promote STI screening and treatment are essential for alleviating these disparities. Self-care, or the care taken by individuals towards their own health and well-being may be such a strategy. This study will assess the efficacy of a self-care intervention, called Protecting Our Future Generation, for increasing uptake of STI screening and impacting sexual risk and protective behaviors among Native American youth and young adults living in a reservation-based community in the Southwestern United States.

Methods

The proposed study is a randomized controlled trial to test the efficacy of a self-care intervention compared to a control condition. Participants will be Native Americans ages 14–26 years old who have had vaginal or anal sex at least once in their lifetime. Participants will be randomized to the intervention which includes: 1) a sexual health self-assessment with embedded clinical prediction tool predicting STI positivity, and 2) personalized messaging with key steps to lower risk for STIs, or the control condition which includes: 1) a self-assessment about water, soda and sugar sweetened beverage consumption, and 2) personalized messaging to meet recommended daily intake. All participants will be offered a self-administered STI test. Participants will complete assessments at baseline, 3- and 6-months follow-up. The primary outcome measure is completion of STI screening.

Discussion

Protecting Our Future Generation is among the first self-care interventions uniquely focused on sexual health among a Native American population, who endure significant sexual health disparities and are under-represented in research. If efficacious, the intervention will be a model of sexual health self-care for Native American youth and young adults adaptable for use in healthcare and community-based settings.

Trial registration

Clinical Trials: http://clinicaltrials.gov; NCT03895320; Registered 03/28/2019.

Sexual behaviours and sexually transmitted infection outcomes in a cohort of HIV-negative men who have sex with men attending sexual health clinics in England

Men who have sex with men (MSM) attending sexual health (SH) clinics are at high risk for HIV acquisition and are disproportionately affected by sexually transmitted infections (STIs). We collected standardised behavioural data from MSM attending clinics to characterise sexual behaviours and identify predictors for HIV and STIs. In 2012–2013, HIV-negative MSM attending five SH clinics in England reported sexual behaviours in the previous three months via a self-administered questionnaire. Behaviours were linked to the individual’s clinical records using national surveillance. The prevalence and incidence of bacterial STIs (gonorrhoea, Chlamydia, lymphogranuloma venereum and syphilis) and incidence of HIV were calculated. Adjusted odds ratios and hazard ratios with 95% confidence interval (CI) were reported for significant predictors. Of 1278 HIV-negative MSM, 54% were of white ethnicity and UK-born and 43% were 25–34 years old. Almost all men reported at least one partner in the last three months. Half reported condomless anal sex and 36% condomless receptive anal intercourse (CRAI). Incidence of bacterial STIs was 46/100 (95%CI 39–54) person years (py) and of HIV was 3.1/100 (95%CI 1.7–5.6) py. A STI at baseline and CRAI with increasing numbers of partners were associated with both incident infections. In this cohort of MSM high-risk behaviours and STIs were prevalent. Engagement in CRAI increased the likelihood of subsequent infection, while men diagnosed with a bacterial STI were at increased risk of a future STI. Clinical and behavioural risk assessments to determine an individual’s risk of infection could allow a more nuanced prevention approach that has greater success in reducing transmission.

Deriving a clinical prediction rule to target sexual healthcare to women attending British General Practices

Some women attending General Practices (GPs) are at higher risk of unintended pregnancy (RUIP) and sexually transmitted infections (STI) than others. A clinical prediction rule (CPR) may help target resources using psychosocial questions as an acceptable, effective means of assessment. The aim was to derive a CPR that discriminates women who would benefit from sexual health discussion and intervention. Participants were recruited to a cross-sectional survey from six GPs in a city in South-East England in 2016. On arrival, female patients aged 16-44 years were invited to complete a questionnaire that addressed psychosocial factors, and the following self-reported outcomes: 2+ sexual partners in the last year (2PP) and RUIP. For each sexual risk, psychosocial questions were retained from logistic regression modelling which best discriminated women at risk using the C-statistic. Sensitivity and specificity were established in consultation with GP staff. The final sample comprised N = 1238 women. 2PP was predicted by 11 questions including age, binge-drinking weekly, ever having a partner who insulted you often, current smoking, and not cohabiting (C-statistic = 0.83, sensitivity = 73% and specificity = 77%). RUIP was predicted by 5 questions including sexual debut <16 years, and emergency contraception use in the last 6 months (C-statistic = 0.70, sensitivity = 69% and specificity = 57%). 2PP was better discriminated than RUIP but neither to a clinically-useful degree. The finding that different psychosocial factors predicted each outcome has implications for prevention strategies. Further research should investigate causal links between psychosocial factors and sexual risk.

Assessing association between IWantTheKit risk quiz tool and sexually transmitted infection positivity in male users for sexually transmitted infection screening

Our previous pilot study during 2010-2013, based on the IWantTheKit (IWTK) home self-collection program for sexually transmitted infections (STIs), showed that voluntary risk score tool predicted STIs well in female volunteers compared to their male counterparts. Risk score became a required part of the IWTK program in August 2013. We investigated association of IWTK risk score and presence of STI in 592 male participants living in Maryland and Washington DC from August 2013 to April 2015. The risk score quiz includes questions on demographic and sexual risk behavior. Data were analyzed using the Cochran-Armitage test for trend to determine if prevalence of STIs (Chlamydia, gonorrhea, or trichomoniasis) increased with the higher risk score category. Overall, 57% of participants were aged < 30 years (mean: 30.1 ± 9.3 years); 42% white, 42% black, and 16% other races. The majority (67%) of participants had medium risk scores of 3-6, followed by high scores of 7-10 (22%), and 0-2 (11%). The overall prevalence of STIs was 10.5% (62/592). The prevalence of STIs was 3.1% for users with risk scores of 0-2, 10.4% for those with scores 3-6, and 14.3% for those with scores 7-10 (trend test: p = 0.019). Medium and high IWTK risk scores successfully predicted the probability of STIs in male participants after elimination of potential selection biases.

Can psychosocial and socio-demographic questions help identify sexual risk among heterosexually-active women of reproductive age? Evidence from Britain's third National Survey of Sexual Attitudes and Lifestyles (Natsal-3)

Background

Contraceptive advice and supply (CAS) and sexually transmitted infection (STI) testing are increasingly provided in primary care. Most risk assessment tools are based on sexual risk behaviours and socio-demographics, for use online or in specialist services. Combining socio-demographic and psychosocial questions (e.g. religious belief and formative experience) may generate an acceptable tool for targeting women in primary care who would benefit from intervention. We aimed to identify psychosocial and socio-demographic factors associated with reporting key sexual risk behaviours among women in the British general population.

Methods

We undertook complex survey analysis of data from 4911 hetero-sexually active women aged 16–44 years, who participated in Britain’s third National Survey of Sexual Attitudes and Lifestyles (Natsal-3), a national probability sample survey undertaken 2010–2012. We used multivariable regression to examine associations between the available psychosocial and socio-demographic variables in Natsal-3 and reports of three key sexual behaviours: a) 2+ partners in the last year (2PP); b) non-use of condoms with 2+ partners in the last year (2PPNC); c) non-use of condoms at first sex with most recent sexual partner (FSNC). We adjusted for key socio-demographic factors: age, ethnicity and socio-economic status (measured by housing tenure).

Results

Weekly binge drinking (6+ units on one occasion), and first sex before age 16 were each positively associated with all three sexual behaviours after adjustment. Current relationship status, reporting drug use (ever), younger age and living in rented accommodation were also associated with 2+ partners and 2 + partners without condoms after adjustment. Currently being a smoker, older age and respondent ethnicity were associated with FSNC after adjustment for all other variables. Current smoking status, treatment for depression (last year), and living at home with both parents until the age of 14 were each associated with one or more of the behaviours.

Conclusions

Reported weekly binge drinking, early sexual debut, and age group may help target STI testing and/or CAS among women. Further research is needed to examine the proportion of sexual risk explained by these factors, the acceptability of these questions to women in primary care and the need to customise them for community and other settings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-016-3918-8) contains supplementary material, which is available to authorized users.

Use of a risk quiz to predict infection for sexually transmitted infections: a retrospective analysis of acceptability and positivity

BACKGROUND

Individuals who are sexually active may want to make a decision as to whether they are at risk for having a sexually transmitted infection (STI) such as Chlamydia trachomatis, Neisseria gonorrhoeae and Trichomonas vaginalis. Our goal was to develop and evaluate a simple self-taken sexual risk quiz for participants, ordering an online STI self-collection test kit to determine whether the score predicted infection status.

METHODS

As part of the IWantTheKit programme for home sample self-collection for STIs, 2010-2013, the programme asked male and female users to voluntarily take a risk quiz. The six-question quiz was about risk behaviour and included an age question. Data analyses were stratified by gender as determined a priori. Scores 0-10 were stratified into risk groups for each gender based on similar risk score-specific STI prevalence. Retrospective analyses were performed to assess whether risk group predicted aggregate STI positivity. Urogenital/rectal mailed samples were tested by nucleic acid amplification tests.

RESULTS

More females (N=836) than males (N=558) provided voluntary risk scores. The percentage of eligible participants who submitted scores was 43.9% for both females and males. There was a higher STI infection rate in females (14.0%) than in males (7.0%) for having any STI (p<0.001). Multivariate logistic analysis for females, which controlled for age and race, demonstrated that a higher risk score group independently predicted risk for having an STI (OR of 2.2 for risk scores 5-7 and 4.2 OR for scores of 8-10). For males, the multivariate model, which controlled for race, indicated that no risk score group was associated having an STI.

CONCLUSIONS

Results of a participant's own sexual risk quiz score independently predicted STI positivity for women, but not for men. Further study of this simple risk quiz is required.

Evaluation of a dilution method for non-evaluable results in the detection of Chlamydia trachomatis and Neisseria gonorrhoeae with the Cobas 4800 platform

INTRODUCTION

A variable percentage of samples analysed using the Cobas 4800 assay can give an invalid result by PCR inhibition or erroneous due to incorrect DNA extraction with the Cobas 4800 CT/NG test.

METHOD

An analysis was performed using the vortex agitation and dilution protocol on the original sample (swab or urine) for a total of 116 samples. In order to analyse the sensitivity of this method, 100 samples (swabs and urine) with known results were retested.

RESULTS

A total of 98.3% (114/116) of the samples analysed were resolved with this protocol with 100% agreement after reviewing clinical data, Gram stain, and other samples analysed in parallel from the same patient.

DISCUSSION

The data indicate no loss of sensitivity with this protocol; thus Cobas 4800 users could use this method without the need for alternative methods.

A validation study of a clinical prediction rule for screening asymptomatic chlamydia and gonorrhoea infections among heterosexuals in British Columbia

BACKGROUND

One component of effective sexually transmitted infections (STIs) control is ensuring those at highest risk of STIs have access to clinical services because terminating transmission in this group will prevent most future cases. Here, we describe the results of a validation study of a clinical prediction rule for identifying individuals at increased risk for chlamydia and gonorrhoea infection derived in Vancouver, British Columbia (BC), against a population of asymptomatic patients attending sexual health clinics in other geographical settings in BC.

METHODS

We examined electronic records (2000-2012) from clinic visits at seven sexual health clinics in geographical locations outside Vancouver. The model's calibration and discrimination were examined by the area under the receiver operating characteristic curve (AUC) and the Hosmer-Lemeshow (H-L) statistic, respectively. We also examined the sensitivity and proportion of patients that would need to be screened at different cut-offs of the risk score.

RESULTS

The prevalence of infection was 5.3% (n=10 425) in the geographical validation population. The prediction rule showed good performance in this population (AUC, 0.69; H-L p=0.26). Possible risk scores ranged from -2 to 27. We identified a risk score cut-off point of ≥8 that detected cases with a sensitivity of 86% by screening 63% of the geographical validation population.

CONCLUSIONS

The prediction rule showed good generalisability in STI clinics outside of Vancouver with improved discriminative performance compared with temporal validation. The prediction rule has the potential for augmenting triaging services in STI clinics and enhancing targeted testing in population-based screening programmes.