Sampling time for self-taking an oropharyngeal swab for gonorrhoea and chlamydia testing

Keywords: Chlamydia trachomatis, Neisseria gonorrhoeae, pharyngeal, screening, self-collected, sexually transmitted diseases, sexually transmitted infection, throat.

Rises in oropharyngeal gonorrhoea and chlamydia have been observed in at-risk populations such as gay, bisexual, and other men who have sex with men (MSM) and sex workers in many countries.^1,2 A correct and accurate sampling method is important for testing. However, there have been no standardised guidelines or recommendations on sampling time for taking an oropharyngeal swab for gonorrhoea and chlamydia testing. In 2021, Stuart and colleagues found that UK sexual health clinicians spent on average 4.6 s taking oropharyngeal swabs for gonorrhoea culture.³ This sampling time was estimated by clinicians, and it may vary between patients. Nucleic acid amplification test (NAAT) has a higher sensitivity than culture for gonorrhoea detection; however, there have been no studies examining the sampling time for taking oropharyngeal swabs for gonorrhoea detected using NAAT.

To minimise the risk of SARS-CoV-2 to healthcare workers during the COVID-19 pandemic, the Melbourne Sexual Health Centre (MSHC) changed from clinician-collected to self-taking oropharyngeal swab in March 2020.⁴ We aimed to determine the sampling time for self-taking oropharyngeal swabs for gonorrhoea and chlamydia testing.

Between 9 November 2021 and 18 January 2022, clients who attended MSHC, who were aged ≥18 years and were tested for oropharyngeal STI, were invited to participate in a study that asked them to record the amount of time they spent on self-taking one oropharyngeal swab for gonorrhoea and chlamydia testing. We also asked the participants how they recorded the time: (1) using a smartphone; (2) self-counting; or (3) other methods. An illustrated instruction on how to take an oropharyngeal swab was placed in the bathroom but there was no recommended sampling time included in the instructions.⁴ All oropharyngeal swabs were tested for both gonorrhoea and chlamydia using NAAT. This study was approved by the Alfred Hospital Ethics Committee (386/20).

There were 215 participants recruited in the study and the characteristics are presented in Table 1. The sampling time ranged from 1 to 123 s, with a median of 8 s (IQR = 5–12). Of the 212 participants who answered the question on how they recorded the sampling time, most used self-counting methods (53.3%; n = 113), followed by smartphone (26.9%; n = 57) and then other methods such as guessing or swabbing until it caused a gag reflex (19.8%; n = 42). However, younger participants tended to use a smartphone and older participants tended to use another method (P < 0.001; Supplementary Table S1). There was a significant difference in sampling time across the three methods (P < 0.001; Fig. 1); the median time was 13 s (IQR = 10–26) for smartphone, 6 s (IQR = 5–10) for self-counting and 5 s (IQR = 3–10) for other methods.

Table 1.  Demographic characteristics of 215 participants.

Fig. 1.  Violin plots and box plots of the sampling time for self-taking oropharyngeal swabs, stratified by three different counting methods. Kruskal–Wallis, P < 0.001. The P-values shown in the figure were calculated using Mann–Whitney U-test when comparing the sampling time between two groups.

The test positivity for oropharyngeal gonorrhoea was 3.3% (7/214) and oropharyngeal chlamydia was 0.9% (2/214). The median sampling time did not differ between oropharyngeal gonorrhoea positive test results vs negative test results (10 s vs 8 s; P = 0.570); and between oropharyngeal chlamydia positive test results vs negative test results (7 s vs 8 s; P = 0.457; Table 2). The small number of oropharyngeal gonorrhoea cases might be due to the changes in sexual practices during the COVID-19 pandemic⁵ and it may not have enough power to detect the differences.

Table 2.  Sampling time for self-taking oropharyngeal swab, stratified by oropharyngeal gonorrhoea and chlamydia positivity.

There have been no standardised guidelines on sampling time for taking an oropharyngeal swab for gonorrhoea and chlamydia testing. Our findings suggest that most individuals spent 8 s on sampling the oropharynx. Some participants swabbed until having a gag reflex, but a past study has shown that there was no association between having a gag reflex and gonorrhoea test positivity using NAAT.⁶ Self-taking nasopharyngeal swabs have become more common since the COVID-19 pandemic and some guidelines recommended swabbing for 10–15 s for COVID-19 testing.^7,8 Self-counting or guessing may not be accurate and it may not be practical to use a smartphone to count; therefore, recommending the number of rotations at tonsils and the posterior pharyngeal wall (e.g. five rotations for COVID-19 sampling) may be easier or more practical for self-taking swabs.⁸

Supplementary material is available online.

All data relevant to the study are included in the article.

CKF and EPFC are Editors of Sexual Health, but they were blinded from the peer-review process for this paper. All other authors declare no conflicts of interest.

This study was funded by an Australian National Health and Medical Research Council (NHMRC) Emerging Leadership Investigator Grant (GNT1172873). EPFC is supported by an NHMRC Emerging Leadership Investigator Grant (GNT1172873). CKF is supported by an Australian NHMRC Leadership Investigator Grant (GNT1172900).

EPFC, TRP and CKF conceived the study. EPFC and TRP designed the study and oversaw the study. EPFC performed data analyses and wrote the first draft of the manuscript. KM, TS, AB and GT were involved in study recruitment. KM and WT were involved in data entry. WT assisted with literature search. All authors were involved in data interpretation, revising the manuscript for important intellectual content and approved the final version. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.