Changes to processing of female genital swabs

Female genital swabs for Gram’s stain are primarily recommended for the diagnosis of bacterial vaginosis (BV) and candidiasis in symptomatic women. Asymptomatic screening for either BV or candidiasis is virtually never indicated, however we receive many such swabs every week.

We have noted that many request forms submitted with female genital swabs provide limited clinical information so it is not possible to determine the clinical indication for the test. A significant number of swabs are referred together with cervical smears from women who are undergoing routine cervical screening and are very unlikely to be symptomatic. This is not recommended practice since the positive predictive value of the Gram’s stain for asymptomatic women has not been validated. Many organisms identified from genital swabs represent commensal flora but may be misinterpreted as infection.

Therefore, routine genital swabs for BV and Candidiasis are not recommended unless symptoms are present. This includes women with an uncomplicated pregnancy or prior to insertion of an intrauterine contraceptive device (IUD).

There is no change to the testing of Aptima swabs for chlamydia/gonorrhoea (CT/NG) NAAT, but note that opportunistic CT/NG testing in asymptomatic women is only recommended for high risk populations, such as women <25 yrs, change in partner, multiple partners etc. The positive predictive value of a positive chlamydia result from a vaginal swab from an asymptomatic women can be as low as 40%, meaning that asymptomatic screening has the potential to do harm from over-diagnosis.

From 28 June 2021 vaginal swabs will not be processed unless appropriate clinical details are provided on the request form.

Genital culture swabs are primarily recommended for:
– diagnosis of bacterial vaginosis (BV), candidiasis or Trichomonas vaginalis (TV) infection in symptomatic women
– investigation of vaginal discharge and STI
– investigation of vaginal thrush which is recurrent or non-responsive to treatment
– as part of TV infection contact tracing

Genital swabs should NOT be performed as part of a “routine screen” taken concurrently with a cervical smear in asymptomatic women.

Treatment of BV is not recommended unless symptoms are present, and Candida can be a normal commensal of the genital tract. As such, female genital swabs for the diagnosis of BV or candidiasis will not be processed unless appropriate clinical details are provided on the request form. Clinical details must indicate the presence of symptoms such as vaginal discharge, itch, burning, ?vaginitis etc. Pre-termination of pregnancy or a high risk pregnancy (previous low birth weight) will also be accepted as indications for testing for BV.

Genital swabs not processed on account of absent clinical details will be stored for three days before being discarded. During this time, referrers can contact the laboratory to discuss specimen processing on 06 872 6462 or email

In addition, we will not be routinely culturing for Candida unless there is a history of failed treatment for vaginal thrush. Candida spp. are part of the normal flora, and to be causing infection they should be present in sufficient numbers to be seen on Gram’s stain.

These changes brings Hawke’s Bay community testing in line with other New Zealand laboratories who have had identical processes since 2017.

For any further information, please contact Dr Tim Blackmore, Clinical Microbiologist
T: 027 271 8606

Download a PDF of this Lab Update here>>.