“Do it yourself” tests for chlamydia could be missing around 80% of cases

Commercially available home tests for chlamydia could be failing to identify between 75% and 83% of people infected when compared with the “gold standard” biochemical lab test, according to new research from the Netherlands.

The study of 772 women found that three “point of care” tests available on the internet and in pharmacies only correctly identified 17-25% of women who had chlamydia according to nucleic acid amplification testing commonly used by GPs and sexual health clinics.

Chlamydia is the most common sexually transmitted infection in the United Kingdom. More than 200,000 people were diagnosed in 2009, the majority of whom were aged 15-24. Around 50% of men and 70-80% of women who get chlamydia will have no symptoms, yet left undiagnosed chlamydia cause infertility.

Point of care tests for chlamydia usually involve the woman taking a vaginal swab herself and sending the sample to a laboratory to be tested, then going for an appointment with her doctor to get the result. Currently testing involves one doctor’s appointment to have a sample taken and a second 1-2 weeks to get the result, which is a much more time consuming approach.

The authors of this study assessed all women over the age of 16 who applied for a consultation at a sexual health clinic in Maastricht between September 2007 and April 2008. A total of 772 women with a median age of 23 were included in the final study.

When nucleic acid amplification testing was used, 11% of these women were found to be infected with Chlamydia trachomatis.

The authors then assessed whether three tests commercially available and certified in Europe – Handilab-C, Biorapid CHLAMYDIA Ag test, and QuickVue Chlamydia test – could identify which women had chlamydia.

The three tests only picked up 17.1-25.0% of women who had chlamydia (sensitivity) and correctly excluded 93.7-99.7% of those who didn’t (specificity). World Health Organization criteria indicate that point of care tests should have a sensitivity of between 43% and 65% and a specificity of 98%.

The sensitivity of two of the tests improved slightly if they were performed within 72 hours of the women taking a vaginal swab. As little as 19.8% of women who tested positive actually had chlamydia, although about 90% of those who tested negative were free from disease.

The results of this study indicate that many infections would have been missed had these point of care tests been used on their own, allowing women to go untreated and potentially spread the infection, and people with false positive results could have been treated unnecessarily.

On this basis the authors state: “In our opinion, the chlamydia point of care tests we have evaluated are not ready for widespread use.”

In an editorial on the topic, Dr Sue Skidmore from the Department of Microbiology at Princess Royal Hospital, Telford, agrees. “It is widely agreed that rapid tests for sexually transmitted infections with high sensitivity and specificity would provide advantages,” she writes, “although the introduction of their use, particularly for home use, needs to be rigorously evaluated and controlled with an assurance that robust quality assurance is in place when appropriate.”

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van Dommelen L et al. (2010) Alarmingly poor performance in Chlamydia trachomatis point-of-care testing. Sexually Transmitted Infections 86:355-359. DOI: 10.1136/sti.2010.042598

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Backpackers in Australia are a sexual health risk

Backpacker AustraliaYoung people, especially Brits, famously head to Australia in their droves in search of travel, adventure, and, crucially, some hot weather.  In 2009-09, 560,105 international backpackers visited Australia, representing 10.9% of all international visitors.

It seems that backpackers in Oz aren’t just looking for fun and sun though – according to a new study they’re also looking for flings, and are bringing sexually transmitted diseases with them.

Research published in the journal Sexually Transmitted Infections has found that international backpackers in Sydney had a higher number of sexual partners and drunk more alcohol than native Australians. Backpackers also had higher rates of chlamydia and more previous sexually transmitted infections than locals.

The authors of this study retrospectively looked through the medical records at the Sydney Sexual Health Centre and identified 5,702 backpackers – people who had been born outside of Australia and been in the country for less than two years – and 7256 comparison patients – natives or people who had lived in the country for longer than 2 years. The average age of the backpacker group was 25 and almost half had come from the UK.

Backpackers were twice as likely to report drinking alcohol at hazardous levels than were comparison patients. More than a quarter (27%) of female backpackers reported drinking more than 17.5 units of alcohol a week, equivalent to about eight glasses of wine, whereas only 14% of comparison women drank at this level. A total of 17% of male backpackers drank more than 35 units of alcohol a week, roughly 15 pints of beer, compared with 5% of comparison men.

About 40% of backpackers reported having had two or more sexual partners in the previous 3 months, compared with 30% of comparison patients.  Interestingly, condom use was low in both the backpacker group and the comparison group: two thirds of each group reported having had unprotected sex.

When it came to rates of sexually transmitted infections, backpackers were more likely to be diagnosed with chlamydia (7% vs 5%) and have a history of sexually transmitted infections (15% vs 10%).  However, locals were more likely to have genital warts.

The authors point out the public health implications of their findings – international backpackers are a potential risk population for either acquiring sexually transmitted diseases or transmitting them to other travellers or local residents.  “Although we could not determine the extent of the risk of transmission to local residents from our study,” they say, “it has been demonstrated that being born overseas or having a partner from overseas was a risk factor for chlamydia infection in Sydney women.”

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McNulty A et al. (2010) The behaviour and sexual health of young international travellers (backpackers) in Australia. Sexually Transmitted Infections DOI: 10.1136/sti.2009.038737

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You’ve got mail… or chlamydia

The young people’s sexual health charity Brook has teamed up with the NHS and the laboratory testing company Preventx to offer free chlamydia testing kits through the post.

By using the Freetest.me website, young people between the ages of 16 and 24 can order a postal home testing kit, return their urine sample or vaginal swab by post, and receive the results by text message, email or on the website’s tracking service.

According to Brook, chlamydia is the most common sexually transmitted infection, with 1 in 10 people affected. Up to 75% of women and 50% of men with chlamydia have no symptoms, but left untreated the disease can cause serious health problems such as pelvic inflammatory disease and scarring of the reproductive system, and can lead to infertility.

Chlamydia can be treated easily with antibiotics, but these drugs can stop the contraceptive pill or patch from working.

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The sexual health of Great Britain

This week the Office for National Statistics released the results of their 2007/08 contraception and sexual health survey, which was undertaken as part of the National Statistics Omnibus Survey.

Over four months, 1,164 women aged 16-49 and 1,543 men aged 16-69 completed a questionnaire on contraception use, sexual health, and knowledge of sexually transmitted infections (STIs). The survey found that the majority of Brits are monogamous. Men still claim to have had more sexual partners than women but at least are mostly using condoms while they’re playing the field. Women, on the other hand, prefer the pill to any other form of contraception. We’re not too hot on emergency contraception but know our STIs better than we used to, gleaning most of our info from the TV.

As many as 75% of men and 78% of women reported having had only one sexual partner in the previous year. Within all age groups, a higher proportion of men than women reported multiple sexual partners and more women than men reported having had just one partner.

The pill was the most popular form of contraception, used by 28% of women employing such measures, and the condom was the second most popular method (24%). In total, 43% men and 50% of women had used a condom in the past year, with those who had had more than one sexual partner more likely to have used a condom than those who had only had one partner. More specifically, 80% of men and 82% of women who had multiple partners had used a condom in the past year.

Almost all women (91%) had heard of the morning after pill, but awareness of the emergency intrauterine device (IUD) had dropped from 49% in 2000/01 to 37% in 2007/08. Less than half (49%) of the women who had heard of emergency contraception knew that the morning after pill is effective up to 72 hours after intercourse, while less than 10% were aware that the emergency IUD was effective if inserted up to five days after sex. Only 6% thought that the morning after pill protected against pregnancy until the next period and less than 1% believed that it protected against sexually transmitted infections.

Nearly all respondents correctly identified that chlamydia is an STI (85% of men and 93% of women), far more than in 2000/01 (35% and 65%, respectively), and nearly all men and women knew that gonorrhoea is an STI (92% and 91%, respectively).

Alarmingly, half of all respondents reported making no changes to their behaviour as a result of what they had heard about HIV/AIDS and other STIs, but thankfully more than a third of men and women said they had increased their use of condoms.

Most respondents got their information on STIs from television programmes (31%), followed by TV adverts (22%), and newspapers, magazines or books (20%). On the other hand, the internet was rarely used as a source of information about STIs, even by young people (3% of those aged 16-24).

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