This question provided a good opportunity to reflect on appropriate use of laboratory tests. The incubation periods
for different pathogens vary, so incorrect timing of testing may provide misleading results. For example: Chlamydia
is 7-21 days, Gonorrhoea is 2-5 days, Trichomoniasis is 4-28 days. It is useful to remind patients, that while laboratory
tests can exclude some organisms, not all sexually transmitted infections can be excluded. In particular screening is
not currently recommended for HSV and HPV.
While it is prudent to delay STI testing for approximately 2 weeks, empirical treatment may be commenced. In most
cases this would be azithromycin for Chlamydia, although empirical treatment for other STIs may be indicated in high
When a patient requests an STI test a full sexual history and examination is indicated to help determine risk and
guide testing. This would typically include a swab (for women) or first void urine (for men) for Chlamydia, collection
of a separate swab for gonorrhoea and trichomonas. Serology testing for HIV, hepatitis B and C, and syphilis will be
guided by findings in history and examination.
Because a range of tests is indicated for patients requesting an STI check, self testing is generally not a recommended
alternative. However the panel were interested to know if a self taken swab or a first void urine (FVU) for gonorrhoea
is useful if a swab is refused.
Some of the panel were also familiar with practice in Australia, in which a single swab is used for both Chlamydia
and gonorrhoea, and they wondered if this approach could be used in New Zealand.
The self collected vaginal swab has been found to be a more sensitive test than FVU for identifying C.trachomatis in
females. Many of the nucleic acid amplification tests (NAAT) used for detection of C.trachomatis also can be
used for the detection of N.gonorrhoeae but there are some issues with the specificity (false positive) tests
as well as the cost. It is also not possible to perform susceptibility testing on these samples.