Trends in different contraception methods among women attending the Melbourne Sexual Health Centre from 2011 to 2020.

OBJECTIVES: The efficacy and availability of contraception have changed in the last several decades; however, unintended pregnancies continue to be an issue in Australia. This study aimed to describe trends in contraception in women attending a sexual health service over 9 years. STUDY DESIGN: Repeated cross-sectional study. METHODS: Women aged 16-49 years attending Melbourne Sexual Health Centre between 2011 and 2020 were included. Women were asked what methods of contraception they currently use. Contraception were categorised into long-acting reversible contraception (LARC; e.g. intrauterine devices and implants classified as highly effective), moderately effective contraception (e.g. oral contraception pill), less effective contraception (e.g. condom and withdrawal) and no contraception, as defined by US Centers for Disease Control and Prevention guidelines. Multivariable logistic regression was used to examine the factors associated with the use of moderate-high-efficacy contraception. RESULTS: A total of 38,288 women were included with a median age of 25 (interquartile range: 22-29). Between 2011 and 2020, there was a decreasing trend in condom (63.3%-56.1%; Ptrend <0.001) and oral contraception (27.2%-20.5%; Ptrend <0.001) use, whilst there was an increasing trend in the use of LARCs: implant (4.6%-6.0%; Ptrend = 0.002) and intrauterine device (2.8%-11.8%; Ptrend <0.001). Increasing age was associated with decreased odds of using moderate-high-efficacy contraception (Ptrend <0.001). Compared with Oceanian-born women, Asian (adjusted odds ratios [aOR] = 0.63, 95% confidence interval [CI]: 0.56-0.72) and Middle Eastern-born women (aOR = 0.60, 95% CI: 0.48-0.74) had lower odds of using moderate-high-efficacy contraception, whilst European (aOR = 1.23, 95% CI:1.07-1.41) and North American-born women (aOR = 1.51, 95% CI: 1.22-1.87) had higher odds of using moderate-high-efficacy contraception. CONCLUSIONS: Between 2011 and 2020, LARC use has increased, whilst less effective contraceptives, such as condom and oral contraception, have decreased among women at Melbourne Sexual Health Centre. Further research is required to understand age and ethnic disparities in contraception methods for future family planning programmes.

Comparison of sucrose and maltose as reinforcers in an operant choice paradigmn.

Two experiments compared the reinforcing effects of sucrose and maltose across a range of concentrations. The results were interpreted using the Multiplicative Hyperbolic Model of reinforcer value (MHM). In Experiment 1, rats were exposed to a discrete-trials schedule in which they chose between the test compound (sucrose or maltose) and a standard sucrose solution (0.4M, delivered after a 4-s delay). Percentage choice of each test compound increased as a function of concentration. The maximum percentage choice of maltose was significantly less than that of sucrose; the concentration corresponding to the half-maximal selection of the test compound was lower for maltose than for sucrose. In Experiment 2 the preference function for sucrose alone was compared with the preference function for a sucrose solution to which a fixed concentration of maltose had been added. The presence of maltose elevated the function and shifted it leftwards (i.e. towards lower concentrations). The results were interpreted in terms of MHM using two alterntive models 'borrowed' from classical pharmacological receptor theory. It was concluded that maltose and sucrose are not fully substitutable reinforcers and that the reinforcing effect of maltose may be mediated by an action at more than one species of sweet taste receptor. (200 words).

Theoretical note: Quantity and concentration as co-determinants of the reinforcing value of sucrose: A re-analysis of some previously published data.

According to the Multiplicative Hyperbolic Model of reinforcer value (MHM), the overall value of a reinforcer may be defined by the multiplicative combination of a set of hyperbolic functions, each of which defines the impact of a particular feature of the reinforcer (e.g., quantity, immediacy of delivery). A previous experiment found that the relationship between the indifference volumes (qA(50)) of reinforcer A (a 0.4-M sucrose solution) and the fixed volume (qB) of reinforcer B (a 0.2-M sucrose solution: 32 - 256 µl) was consonant with this model. This paper describes a re-analysis of those data in an attempt to identify the nature of the effect of concentration on the two parameters of the size/value hyperbola (asymptote, ε, and sensitivity, Q). Comparison of two versions of the model in which (i) both parameters were free to vary as a function of qB and (ii) only ε was free to vary, showed that the latter model provided a satisfactory account of the data and that the inclusion of Q as an additional free parameter was not justified. Implications for the development of MHM are discussed.

Further observations on the reinforcing value of sucrose solutions: Interaction between quantity and concentration.

According to the Multiplicative Hyperbolic Model of reinforcer value (MHM), the value of a reinforcer is an increasing hyperbolic function of its size. In addition it is generally accepted that in the case of soluble reinforcers such as sucrose, value is an increasing function of molar concentration. The present experiment examined the interaction between size and concentration on the effectiveness of sucrose reinforcers in an operant choice paradigm. Rats were trained under an adjusting-magnitude schedule in which a response on lever B delivered a fixed volume of a sucrose solution, while a response on lever A delivered a 0.8-M sucrose solution, the volume of which, qA, was adjusted according to the rats' choices. When B was preferred in a given block of trials, qA was increased in the following block; when A was preferred, qA was reduced in the following block. The concentration and volume of B (cB, qB) were varied across six phases of the experiment and the corresponding indifference magnitudes of A (qA(50)) were measured. Log qA(50) increased and qB/qA(50) declined as approximately linear functions of log cB, consistent with the supposition that reinforcer value was determined by multiplicative combination of hyperbolic expressions representing concentration and volume.

The effect of adulteration with a bitter tastant, denatonium benzoate, on the reinforcing value of sucrose.

According to the Multiplicative Hyperbolic Model of reinforcer value (MHM), the value of a reinforcer is an increasing hyperbolic function of its size (q). A recent experiment examined the effect of adulterating a sucrose solution with citric acid on the value of a sucrose reinforcer. In contrast to expectations derived from MHM, the effect of citric acid was consistent with the summation of positive (sucrose) and negative (citric acid) values. The present experiment extended these observations to a bitter tastant, denatonium benzoate (DB). Rats were trained under an adjusting-magnitude schedule in which a response on lever B delivered a fixed volume of a sucrose/DB mixture, while a response on lever A delivered a sucrose solution, the volume of which, qA, was adjusted according to the rats' choices. When B was preferred in a given block of trials, qA was increased in the following block; when A was preferred, qA was reduced in the following block. qB was varied across five phases of the experiment and the corresponding indifference magnitudes of A were measured. The results indicated that, as was the case with citric acid, the value of the mixture reflected the summation of positive (sucrose) and negative (DB) values.

Adulteration of sucrose with citric acid: Effect on reinforcing value, examined using an adjusting-magnitude schedule of reinforcement.

According to the Multiplicative Hyperbolic Model (MHM), the value of a reinforcer is an increasing hyperbolic function of its size (q). Recently reported results indicated that dilution of a sucrose solution reduced its reinforcing value by increasing the 'size-sensitivity' parameter of this function and reducing its maximum. The present experiment examined whether adulterating a sucrose solution with citric acid would have a similar effect on the hyperbolic function. Rats were trained under an adjusting-magnitude schedule in which a response on lever B delivered a fixed volume of a sucrose/citric-acid mixture, while a response on lever A delivered a sucrose solution, the volume of which, qA, was adjusted according to the rats' choices. When B was preferred in a given block of trials, qA was increased in the following block; when A was preferred, qA was reduced in the following block. qB was varied across four phases of the experiment and the corresponding indifference magnitudes of A were measured. The results failed to support the hypothesis that adulteration with citric acid resulted in devaluation of sucrose. An alternative hypothesis derived from MHM, that the value of the mixture reflected the summation of positive (sucrose) and negative (citric acid) values, is discussed.

Changes in sow milk lipidome across lactation occur in fatty acyl residues of triacylglycerol and phosphatidylglycerol lipids, but not in plasma membrane phospholipids.

Milk fats are vital to neonate survival and development, but vary highly by diet, maternal metabolic state and stage of lactation. To gain a better understanding of changes in lipid composition of sow milk across lactation, milk was collected from nine multiparous sows on days 0, 3, 7, and 14, relative to birth and lipids were profiled using multiple reaction monitoring (MRM) profiling. Percent fat was determined by creamatocrit, and found to be different (P < 0.05) between day 0 (12.36 ± 5.90%) and day 3 (16.22 ± 3.65%) but not between day 7 (13.13 ± 2.19%) and day 14 (12.13 ± 2.45%). Fat was extracted from milk (n = 6/day) using the Bligh-Dyer method and profiled using tandem mass spectrometry MRM to determine the abundance of lipids defined by class and fatty acyl residue composition. Lipid species relative concentration was calculated from internal standards, and data analysis was performed using Metaboanalyst 4.0. Concentration of phosphatidyl-choline, -serine, -ethanolamine, -inositol, cholesteryl ester and sphingomyelin did not vary across lactation days, nor did the distribution of associated fatty acyl residues. The total abundance of triacylglycerides (TGs) and phosphatidylglycerols (PGs) increased (P < 0.05) from colostrum (day 0) to transitional (days 3 and 7) and mature milk (day 14). As lactation days increased from day 0 to day 14, the number of carbons and unsaturation within fatty acyl residues decreased (P < 0.05) in both TGs and PGs. The proportion of TGs and PGs increased (P < 0.05) relative to other lipid classes. Changes in composition of milk triglycerides and phosphatidylglycerols likely reflect the metabolic activity of the mammary gland and developmental needs of neonates.

Sex is associated with the persistence of non-optimal vaginal microbiota following treatment for bacterial vaginosis: a prospective cohort study.

OBJECTIVE: Determine the associations between factors and sexual practices and the composition of the vaginal microbiome (VM) of women treated for bacterial vaginosis (BV). DESIGN: Prospective cohort study. SETTING: The Melbourne Sexual Health Centre, Melbourne, Australia. POPULATION: Seventy-five reproductive-age women diagnosed with clinical BV, treated with first-line antibiotics and followed for up to 6 months. METHODS: Women self-collected vaginal swabs and completed questionnaires at enrolment, the day following antibiotics and monthly for up to 6months until BV recurrence or no BV recurrence (n = 430 specimens). Bacterial composition was determined using 16S rRNA gene amplicon sequencing. The effects of ongoing factors on VM composition (utilising 291 monthly specimens) were assessed using generalised estimating equations population-averaged models, which accounted for repeated measures within individuals. MAIN OUTCOME MEASURES: The relative abundance of vaginal bacterial taxa. RESULTS: Women who reported ongoing sex with a regular sexual partner (RSP) had a VM comprised of increased relative abundance of non-optimal BV-associated bacteria (Adjusted co-efficient [Adjusted co-eff] = 11.91, 95% CI 3.39to20.43, P = 0.006) and a decreased relative abundance of optimal, Lactobacillus species (Adjusted co-eff = -12.76, 95% CI -23.03 to -2.49, P = 0.015). A history of BV was also associated with a decreased relative abundance of Lactobacillus spp. (Adjusted co-eff = -12.35, 95% CI -22.68, P = 0.019). The relative abundance of Gardnerella, Atopobium and Sneathia spp. increased following sex with an RSP. CONCLUSIONS: Sex with an untreated RSP after BV treatment was associated with a VM comprised of non-optimal BV-associated bacteria. BV treatment approaches may need to include partner treatment if they are to achieve a sustained optimal VM associated with improved health outcomes. TWEETABLE ABSTRACT: Sex drives a return to a 'non-optimal' vaginal microbiota after antibiotics for bacterial vaginosis.

Homelessness, sex and a tale of two sexually transmitted infections.

The Young People's Health Service (YPHS) is a free, nurse-led Primary Health Care Clinic, in Melbourne, for young people aged 12-24 who are experiencing homelessness. Sexually transmitted infection (STI) screening is routinely offered as part of comprehensive psychosocial assessments. We wanted to determine the number of people positive for Chlamydia trachomatis (Ct) and Mycoplasma genitalium (Mg), amongst this asymptomatic high-risk population. We also wanted to review our screening practice. All asymptomatic sexually active clients seen by YPHS between 2014 and 2016 were offered a first pass urine polymerase chain reaction-based test for Ct and Mg. Urine samples were taken for men and women. Positivity for Ct and Mg out of those tested was determined and association with gender examined. Between 2014-2016, 272 males and 278 females (n = 550) were screened for Ct, and 72 infections were detected (13.1%. Chlamydia positivity did not differ between males (n = 35; 12.9%, 95% confidence interval [CI]: 8.8-16.8) and females (n = 37; 13.3%, 95%CI: 9.3-17.3). Over the same period 273 males and 284 females were screened for Mg (n = 557) and 55 infections were detected (9.9%). A higher proportion of females (n = 35; 12.3%, 95%CI: 8.5-16.1) tested positive compared to males (n = 20; 7.3%, 95%CI: 4.2-10.4), p = 0.048. Our study demonstrates both Ct and Mg are prevalent in the population, Mg being more common in young women than young men. Referral for specialist care for macrolide-resistant Mg increased and the updated Australian STI management guidelines led to a review of practice.

A custom amplicon sequencing approach to detect resistance associated mutations and sequence types in Mycoplasma genitalium.

BACKGROUND: Mycoplasma genitalium resistance to antibiotic treatments is increasing, with very limited treatment alternatives on the horizon. Surveillance via sequencing of multiple M. genitalium loci would allow: monitoring of known antibiotic resistance mutations, associations between resistance/treatment failure and specific mutations, and strain typing for epidemiological purposes. In this study we assessed the performance of a custom amplicon sequencing approach, which negates the cost of library preparation for next generation sequencing. METHODS: Fifty-two M. genitalium positive samples (cervical, vaginal, anal and rectal swabs, and urine) were used. Three regions associated with M. genitalium antibiotic resistance (23S rRNA, parC and gyrA genes) were targeted, in conjunction with a locus used for differentiation of sequence types in the mgpB gene, and findings compared to Sanger sequencing. RESULTS: Amplicon sequencing provided adequate sequence read coverage (>30×) for the majority of samples for 23S rRNA gene (96%) and mgpB (97%), parC (78%) and gyrA (75%). Single nucleotide polymorphisms (SNPs) were characterised in samples for 23S rRNA gene (94%), parC (56%) and gyrA (4%). Unlike Sanger sequencing, mixed mutations could be identified by the amplicon sequencing method, and ratios of mutation types determined. All results, with one exception, were concordant to Sanger sequence results. Sequence diversity in the mgpB region was represented by 15 sequence types, 4 being observed in multiple samples. CONCLUSIONS: We have demonstrated the utility of this custom amplicon sequencing approach for generating highly informative datasets with the capacity to identify and determine ratios of mixed sequences. The use of this customisable amplicon sequencing method enables cost effective, scalable amplicon sequencing of multiple target regions of interest in M. genitalium.

Choice between different concentrations of sucrose in an adjusting-magnitude schedule: Evidence for reinforcer-specific value maxima.

According to the Multiplicative Hyperbolic Model (MHM), an extension of Mazur's (1987) model of delay discounting, the value of a reinforcer is an increasing hyperbolic function of its size (q). This experiment tested a prediction based on a revised version of MHM (MHM-R), according to which the maximum value may differ between different reinforcers, a possibility not envisaged in MHM. Rats were trained under a discrete-trials adjusting-magnitude schedule in which a response on lever B delivered a dilute sucrose reinforcer (0.2 M) of fixed volume, qB, while a response on lever A delivered a more concentrated sucrose solution (0.4 M) the volume of which, qA, was adjusted according to the rats' choices. When B was preferred in a given block of trials, qA was increased in the following block; when A was preferred, qA was reduced in the following block. qB was varied across four phases of the experiment and the corresponding indifference magnitudes of A (qA(50)) were measured. In keeping with expectations based on both MHM and MHM-R, qA(50) increased approximately linearly with qB, and 1/qA(50) with 1/qB. The ratio qB/qA(50) increased linearly with qB with a positive intercept, a finding that is consistent with MHM-R but not with MHM.

In search of a definition of reinforcer value: Some successes and failures of the multiplicative hyperbolic model.

The concept of 'value' has enjoyed a central position in many theoretical accounts of choice behaviour. Several definitions of 'value' are contrasted in this paper, and one particular approach is defended, whereby value is defined as a dimensionless intervening variable. This definition is a cornerstone of the multiplicative hyperbolic model of choice (MHM), which was proposed twenty years ago as a modification of Mazur's (1987) hyperbolic model of delay discounting. This paper reviews some of the merits and shortcomings of MHM, and suggests some ways in which MHM might be extended and improved. A formal link between 'value' and the related concept of 'response strength' is suggested, and revisions of the model are proposed which may enable it to accommodate several behavioural phenomena not considered in the original formulation. Broadening the scope of MHM comes at the cost of adding to its burden of free parameters, and it is emphasised that addition of any new parameters needs empirical justification. The status of value as a dimensionless intervening variable is upheld; however it is noted that a growing body of empirical evidence for links between neurobiological phenomena and value suggests that interpretation of value as a hypothetical construct may be warranted.

The impact of sample storage on molecular-based detection of Mycoplasma genitalium.

AIMS: Mycoplasma genitalium causes a common, sexually transmitted bacterial infection. This study assessed the detection of M. genitalium in stored urine samples to understand the impact of sample storage on M. genitalium detection. METHODS: Aliquots of M. genitalium-positive urine (n = 20 patients) were stored at either room temperature (22°C) or 4°C, without a preservative. At weekly intervals, samples were tested using the commercial test ResistancePlus MG® (SpeeDx® , Australia). We report the analysis at 1 week, an acceptable collection-to-test turnaround time, with further analysis over 5 weeks to illustrate degradation trends. RESULTS: After storing at 4°C, the proportion of specimens that remained positive for M. genitalium was 100% after 1 week and 95% after 4 weeks. Storage at 22°C led to more rapid decline in detection in the first 4 weeks, with 95% detected after 1 week and 85% at 2 weeks onwards. At 5 weeks, samples stored at both temperatures had an 85% M. genitalium detection rate, with increase in crossing points (Cq) of 0·72 (95% confidence interval (CI) 0·01-1·43; P-trend = 0·027) at 4°C, and 1·75 ((95% CI 0·79-2·71), P-trend <0·001) at 22°C. CONCLUSIONS: Urine samples stored without preservative, and unfrozen, retained high M. genitalium detection levels over the short term (up to 5 weeks). To minimize degradation, storing at 4°C is recommended. SIGNIFICANCE AND IMPACT OF THE STUDY: There is little known about the stability of clinical samples for M. genitalium detection. This study found that a high proportion (85-100%) of samples are still suitable for M. genitalium detection after storage for up to 5 weeks.

The barriers to linkage and retention in care for women living with HIV in an high income setting where they comprise a minority group.

Women comprise a minority population of individuals living with HIV in Australia, and are often poorly represented in research and clinical trials so their needs remain largely unknown. Data suggests that they are diagnosed later than men and start antiretroviral therapy at a lower CD4 cell count. This raises the question whether there are sex specific barriers to linkage and retention in care. This study analyzed 484 surveys received from clinicians collecting demographic, virological, and reproductive health data along with perceived barriers to linkage and retention in care. Most women (67%) were estimated to have been linked into care within 28 days of diagnosis. For women who were not linked into care for more than 28 days, the most commonly reason cited was fear of disclosure to others, followed by fear of disclosure to their partner. The main reasons given for non-retention in care were related to transport, carer responsibilities, financial pressure, health beliefs and concern about stigma or disclosure.

Levels of Mycoplasma genitalium Antimicrobial Resistance Differ by Both Region and Gender in the State of Queensland, Australia: Implications for Treatment Guidelines.

Mycoplasma genitalium is frequently associated with urogenital and rectal infections, with the number of cases of macrolide-resistant and quinolone-resistant M. genitalium infection continuing to increase. In this study, we examined the levels of resistance to these two common antibiotic treatments in geographically distinct locations in Queensland, Australia. Samples were screened for macrolide resistance-associated mutations using a commercially available kit (ResistancePlus MG; SpeeDx), and quinolone resistance-associated mutations were identified by PCR and DNA sequencing. Comparisons between antibiotic resistance mutations and location/gender were performed. The levels of M. genitalium macrolide resistance were high across both locations (62%). Quinolone resistance mutations were found in ∼10% of all samples, with a number of samples harboring mutations conferring resistance to both macrolides and quinolones. Quinolone resistance was higher in southeast Queensland than in north Queensland, and this was consistent in both males and females (P = 0.007). The M. genitalium isolates in rectal swab samples from males harbored high levels of macrolide (75.9%) and quinolone (19%) resistance, with 15.5% harboring resistance to both classes of antibiotics. Overall, the lowest observed level of resistance was to quinolones in females from north Queensland (1.6%). These data highlight the high levels of antibiotic resistance in M. genitalium isolates within Queensland and the challenges faced by sexually transmitted infection clinicians in managing these infections. The data do, however, show that the levels of antibiotic resistance may differ between populations within the same state, which has implications for clinical management and treatment guidelines. These findings also support the need for ongoing antibiotic resistance surveillance and tailored treatment.

ALLIANCE perspectives on integration of humans and the environment into the system of radiological protection.

Risks posed by the presence of radionuclides in the environment require an efficient, balanced, and adaptable assessment for protecting exposed humans and wildlife, and managing the associated radiological risk. Exposure of humans and wildlife originate from the same sources releasing radionuclides to the environment. Environmental concentrations of radionuclides serve as inputs to estimate the dose to man, fauna, and flora, with transfer processes being, in essence, similar, which calls for a common use of transport models. Dose estimates are compared with the radiological protection criteria for humans and wildlife, such as those developed by the International Commission on Radiological Protection. This indicates a similarity in the approaches for impact assessment in humans and wildlife, although some elements are different (e.g. the protection endpoint for humans is stochastic effects on individuals, whereas for wildlife, it is deterministic effects on species and ecosystems). Human and environmental assessments are consistent and complementary in terms of how they are conducted and in terms of the underlying databases (where appropriate). Not having an integrated approach may cause difficulties for operators and regulators, for communication to stakeholders, and may even hamper decision making. For optimised risk assessment and management, the impact from non-radiation contaminants and stressors should also be considered. Both in terms of the underlying philosophy and the application via appropriate tools, the European Radioecology Alliance (ALLIANCE) upholds that integration of human and ecological impact and risk assessment is recommended from several perspectives (e.g. chemical/radiological risks).

Effects of sucrose concentration on choice in an adjusting-magnitude schedule.

Rats were trained under a discrete-trials adjusting-magnitude schedule in which a response on lever A delivered either a larger or a smaller sucrose reinforcer (qA1 = 8 µl, qA2 = 64 µl) with equal probability, while a response on B delivered a reinforcer whose size qB was adjusted according to the rats' choices. When A was preferred in a given block of trials, qB was increased in the following block; when B was preferred, qB was reduced in the following block. The oscillating changes in qB, analysed by the Fourier transform, could be described by a power spectrum whose dominant frequency corresponded to a period of 40-50 trial blocks. The equilibrium value of qB (qB(50)) was inversely related to sucrose concentration; it significantly exceeded the arithmetic mean of qA1 and qA2 when the concentration was 0.2 or 0.4 M, but not when it was 0.8 or 1.6 M. Analysis by mixed-effects modelling revealed a trend for the power of oscillation of qB to increase monotonically with sucrose concentration; the period of oscillation was not systematically related to sucrose concentration. These results are consistent with predictions derived from a revised version of the multiplicative hyperbolic model of intertemporal choice.

Marine radioecology after the Fukushima Dai-ichi nuclear accident: Are we better positioned to understand the impact of radionuclides in marine ecosystems?

This paper focuses on how a community of researchers under the COMET (CO-ordination and iMplementation of a pan European projecT for radioecology) project has improved the capacity of marine radioecology to understand at the process level the behaviour of radionuclides in the marine environment, uptake by organisms and the resulting doses after the Fukushima Dai-ichi nuclear accident occurred in 2011. We present new radioecological understanding of the processes involved, such as the interaction of waterborne radionuclides with suspended particles and sediments or the biological uptake and turnover of radionuclides, which have been better quantified and mathematically described. We demonstrate that biokinetic models can better represent radionuclide transfer to biota in non-equilibrium situations, bringing more realism to predictions, especially when combining physical, chemical and biological interactions that occur in such an open and dynamic environment as the ocean. As a result, we are readier now than we were before the FDNPP accident in terms of having models that can be applied to dynamic situations. The paper concludes with our vision for marine radioecology as a fundamental research discipline and we present a strategy for our discipline at the European and international levels. The lessons learned are presented along with their possible applicability to assess/reduce the environmental consequences of future accidents to the marine environment and guidance for future research, as well as to assure the sustainability of marine radioecology. This guidance necessarily reflects on why and where further research funding is needed, signalling the way for future investigations.

Anorectal swabs as a marker of male-to-male sexual exposure in STI surveillance systems.

Identification of priority populations such as men who have sex with men (MSM) is important in surveillance systems to monitor trends of sexually transmitted infections (STIs). We explored using routinely collected non-behavioural data as a means to establish MSM status in surveillance by assessing anorectal swab as a marker of male-to-male sexual exposure. We used chlamydia testing data from a sexual health clinic, 2007-2012. Men reporting any male sexual partner(s) in the previous 12 months were considered MSM. The dataset was split into development and validation samples to develop a univariate predictive model and assess the model fit. The dataset included 30 358 individual men and 48 554 episodes of STI testing; 45% were among reported MSM and an anorectal swab was performed in 40% of testing episodes. Anorectal swabbing had good diagnostic performance as a marker for MSM status (sensitivity = 87%, specificity = 99%, positive predictive value = 98·6%, negative predictive value = 90·3%). The model showed good fit against the internal validation sample (area under the curve = 0·93). Anorectal swabs are a valid marker of MSM behaviour in surveillance data from sexual health clinics, and they are likely to be particularly useful for monitoring STI trends among MSM with higher risk behaviour.