Testing for chlamydia and gonorrhoea in men who have sex with men (MSM) and trans-women is
recommended every three months for those taking HIV Pre-Exposure Prophylaxis (PrEP). Testing
requires throat and bottom samples, and samples from the urethra (wee-pipe), usually a urine
sample. However, many sexual health services struggle to afford the costs of these 3-samples,
four-times per year, which may restrict numbers given PrEP.
The investigators' previous research has shown that the 3-samples (throat, bottom, urine) can
be combined into one pooled specimen to accurately find gonorrhoea and reduce laboratory
costs. However, the chlamydia results of pooled samples were not as good, finding only 92 out
of 100 infections compared with 99 out of 100 with 3 separate samples. The investigators'
past research showed no difference in diagnostic accuracy between clinician and self-taken
rectum and pharynx swabs for NG and CT detection. People prefer to take their own swabs and
self-taken swabs were more cost effective than clinician taken. Self-taken swabs are now used
routinely in clinical practice and are available as on-line ordered commercial kits.
This study aims to improve the accuracy of chlamydia results by comparing two new pooling
methods with the 3-samples tested separately.
MSM, and trans-women, aged 18 years or over, attending a large UK city sexual health service
for chlamydia and gonorrhoea testing will be invited to take part in the study.
The pooling methods will be: 1) pooling with a smaller amount of urine to reduce the dilution
of the other samples; and 2) pooling with a swab sample from the outside of the tip of the
penis (meatal swab) instead of urine. Meatal swabs are taken by the person themselves. The
swab does not go inside the penis so is easy to do and not painful. Studies suggest meatal
swabs may be better at finding chlamydia than urine samples.
To ensure an accurate comparison, the order of taking the two pooling method samples, and the
3-samples tested separately, will be randomised.
The study will recruit 1250 participants. This is a large enough number to show if either of
the pooling methods can detect more chlamydia than 92 out of 100 infections.
If a pooling technique was developed for MSM and trans-women that did not reduce diagnostic
sensitivity, this would likely be implemented. A sensitive, low-cost, method of triple-site
STI testing, available on-line, or using minimal in-house staff, would enable increased
testing. The investigators believe this study will identify such a method by using meatal
swabs or a reduced urine volume. The reduced diagnostic costs of almost two-thirds would
enable sexual health clinics to provide PrEP to more people, and/or utilise the money saved
elsewhere in their service.