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Original article
Is non-invasive testing for sexually transmitted infections an efficient and acceptable alternative for patients? A randomised controlled trial
  1. L Brown1,
  2. S Patel2,
  3. N J Ives2,
  4. C McDermott1,
  5. J D C Ross1
  1. 1Whittall Street GUM Clinic, Birmingham, UK
  2. 2Birmingham Clinical Trials Unit, University of Birmingham, Birmingham, UK
  1. Correspondence to Miss L Brown, Whittall Street Clinic, Department GU Medicine, Whittall Street, Birmingham B4 6DH, UK; louise.brown{at}


Objectives A randomised controlled trial was conducted to assess and quantify the efficacy and acceptability of non-invasive testing (NIT) for sexually transmitted infections (STI) in asymptomatic patients within a genitourinary medicine clinic.

Methods Patients were randomly assigned to either standard of care (SOC—STI testing with genital examination) or NIT. The length of time patients spent in the clinic was recorded and patients were asked to complete a satisfaction survey.

Results 391 participants were randomly assigned. The length of time male and female patients spent in the clinic was significantly shorter with NIT (men 26 min; women 23 min) compared with SOC (men 41 min; women 45 min, p<0.0001), but most of this decrease was due to reduced patient waiting time within the clinic, rather than less time spent with medical or nursing staff. Those randomly assigned to NIT were significantly more likely to state they were in clinic for less time than expected (p<0.01) and report that the tests were less uncomfortable than expected (p≤0.04). For both men and women, more patients in the SOC group declined testing for syphilis (14%) and HIV (20%) compared with NIT (7% and 13%, respectively), but this was only significantly different between treatments for female patients (p≤0.02).

Conclusions NIT for STI in asymptomatic patients can reduce the time patients spend in the clinic when combined with appropriate patient care pathways, and is an acceptable alternative to physician-taken genital swabs.

  • genitourinary medicine
  • non-invasive testing
  • patient satisfaction
  • patients' views
  • randomised controlled trial
  • self-sampling
  • service delivery
  • sexual health
  • sexually transmitted infection
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Technologies to test for sexually transmitted infections (STI) using nucleic acid amplification testing (NAAT) of urine and self-taken vaginal swabs are highly sensitive and specific.1 Initially their uptake was slow, but NAAT testing is now widespread, including in the National Chlamydia Screening Programme.2 Using non-invasive testing (NIT) to screen for STI could potentially improve the efficiency of sexual health clinics, as reducing the time individual patients spend with healthcare staff means more patients can be seen. This is of particular relevance since the UK Department of Health introduced a 48 h waiting time target for genitourinary medicine services3 leading to clinics having to consider alternatives to traditional practice to help improve capacity. NIT may also be more acceptable to patients than a genital examination with genital swab sampling.

Although NIT for STI is now widely used, a formal randomised comparison with the standard screening method (genital examination and swabs) had not previously been performed. It is regarded as best practice to obtain service users views when considering changes in service delivery,4 and services benefit from this feedback by ensuring they deliver patient-centred outcomes. Therefore, the aim of this study was to assess and quantify the efficacy and acceptability of NIT for STI in asymptomatic patients presenting for STI testing.


Participants were recruited from a city centre genitourinary medicine clinic. Demographics of new patient attendance during the trial were similar to those recruited. Patients were approached by a research nurse after registration at the clinic, but before they saw a doctor or nurse, and their eligibility was assessed using a screening proforma. Asymptomatic male and female patients (>16 years of age) attending clinic for the first time or with a new problem (ie, had not attended clinic in the past month) were eligible. Patients were not eligible if they had genitourinary symptoms, were pregnant, were a known contact of a STI or reported anal intercourse within the past 3 years. Eligible patients were invited to participate in the study and given a patient information sheet with time to read it and ask questions. If the patient agreed to enter the study, written informed consent for study participation was sought at the same clinic visit.

Patients were randomly assigned by telephone by the Birmingham Clinical Trials Unit. Allocation to screening using NIT or standard of care (SOC) with genital examination and swabs was performed using a computer-generated randomisation sequence. Randomisation was stratified by gender, as the process and experience within clinic are different for men and women. Trial participants and those administering the intervention were not blinded to the treatment assignment after allocation.

Patients randomly assigned to SOC were seen by a doctor or nurse who took a sexual history from the patient and performed routine STI screening. Men had swab samples taken from the urethra for gonorrhoea culture and chlamydia NAAT, and women had a speculum examination with swabs taken from the vagina, cervix and urethra for gonorrhoea culture, chlamydia NAAT and Trichomonas vaginalis culture.

Those randomly assigned to NIT had a sexual history taken by a nurse, then men provided a urine sample and women provided a self-taken vaginal swab. Both urine samples and vaginal swabs were tested for gonorrhoea and chlamydia using NAAT (Roche PCR Amplicor; Roche, Burgess Hill, UK). Any patients found after NIT to have a positive NAAT for gonorrhoea were advised to return for a culture test to confirm the diagnosis and establish antibiotic sensitivities.

Patients in both study arms were offered a throat swab for Neisseria gonorrhoeae culture if they gave a history of fellatio. This was taken by the research nurse in the NIT arm or healthcare assistant chaperone in the SOC arm. Syphilis, HIV and, if indicated, hepatitis B testing were also offered to all patients. After STI screening, all patients were asked to complete a short questionnaire to assess the acceptability of the STI screening they had received and their experience within the clinic.

We tested the hypothesis that NIT for STI in asymptomatic patients would reduce the length of the clinic visit and increase patient satisfaction. The primary outcome measure was the length of time patients spent in the clinic. A clinic visit consisted of the patient having a consultation with a doctor or senior nurse, undergoing STI screening and having a blood sample taken. ‘In’ and ‘out’ times were recorded for each patient at each of these three stages. The total time in the clinic was defined as the difference between the ‘in time’ at the initial doctor/nurse consultation and the ‘out time’ following venepuncture (including patient waiting time in the clinic between each stage of the patient visit). Secondary outcomes were the time taken for each of the three stages individually (excluding waiting time between each stage), patient acceptability of the STI screening methods (using a patient self-completed satisfaction survey) and the detection rates of STI.

Patients were analysed in the treatment group to which they were randomly assigned on an intention-to-treat basis. Men and women were analysed separately. Continuous variables (eg, time) were compared using t tests and Wilcoxon tests, with the results presented as mean differences between the two arms with 95% CI. Categorical variables (eg, in the satisfaction survey) were compared using χ2 or Fisher's exact tests. All analysis was performed in SAS (version 9.1).

Data from our clinic database suggested that clinic visits for women last approximately 70 min (SD 30.92) and for men approximately 47 min (SD 24.27). To detect a 20% reduction in the time patients spend in clinic with 80% power (α=0.05) would require 110 patients per arm for men and 80 per arm for women. To allow for drop-outs and loss to follow-up, we aimed to randomly assign 400 patients (200 men and 200 women, split equally between the two arms).


Between 15 March 2006 and 29 September 2006, 1303 patients were approached to enter the study, with 391 of these patients being randomly assigned—204 men (103 SOC vs 101 NIT) and 187 women (94 SOC vs 93 NIT) (figure 1). Four female patients (two in each arm) withdrew from the trial. Two patients were subsequently found to be ineligible and no further data were collected, and two patients changed their minds after randomisation and withdrew consent (figure 1). A further eight patients (three men (two SOC and one NIT) and five women (one SOC and four NIT)) for whom no time data were recorded and a satisfaction survey not completed were considered lost to follow-up. There were also three patients in the SOC arm (one man and two women) who disclosed an exclusion criterion of anal sex after randomisation. Data were collected on these patients, so they were included in the analysis; thus 379 patients (201 men and 178 women) completed the study.

Figure 1

CONSORT diagram—patient recruitment and follow-up through the trial. NIT, non-invasive testing; SOC, standard of care; STI, sexually transmitted infection.

The mean age at randomisation was 28 years for men and 24 years for women, and approximately half were of white British ethnic origin (table 1). For both genders, approximately half of the patients had had a previous check-up for a STI, but only a quarter of patients self-reported a previous infection (usually chlamydia).

Table 1

Baseline characteristics of the patients in the trial

For both men and women, the mean time spent in the clinic was significantly shorter with NIT compared with SOC (table 2). Male patients randomly assigned to SOC were in clinic for on average 41 min compared with 26 min for those randomly assigned to NIT, a mean difference of 15.2 min (95% CI 9.3 to 21.0 min; p<0.0001). This was similar for female patients, for whom the average time in clinic was 45 min in the SOC arm compared with 23 min in the NIT arm, a mean difference of 22.1 min (95% CI 17.2 to 26.9 min; p<0.0001).

Table 2

Summary of time patients spent in clinic

A comparison of the three stages that make up a patient clinic visit (consultation with doctor/nurse, taking screening tests and venepuncture time) found that NIT significantly reduced the consultation time for women (SOC 7.4 vs NIT 6.2 min; p=0.009), but not men (SOC 6.6 vs NIT 7.1 min; p=0.3) (test for interaction p=0.007; table 2). The time taken for STI screening in men was significantly lower with NIT (SOC 3.5 vs NIT=2.7 min; p=0.0008), but there was no difference in women (SOC5.7 vs NIT=5.4 min; p=0.4) (test for interaction p=0.3). There was no difference in venepuncture time between the two arms for either gender.

Health carer time was defined as actual time spent with a member of the clinic staff, excluding waiting times between seeing different staff members. Health carer time (for consultation and STI screening, excluding venepuncture time and waiting time between seeing different staff members) was shorter with NIT for both genders (men SOC 10.1 vs NIT 9.7 min; p=0.5; women SOC 13.2 vs NIT 11.6 min; p=0.03; table 2). The total time spent with clinic staff (consultation, screening and venepuncture time, excluding waiting time) was also slightly reduced with NIT (men SOC 15 vs NIT 13.6 min; p=0.06; women SOC 18.1 vs NIT 16.1 min; p=0.02).

Three hundred and thirty-one (87%) of the 379 patients completed the satisfaction survey questionnaire (table 3). There were no significant differences in age, gender or ethnicity between those who did or did not complete the satisfaction survey. Although a majority of patients in both arms stated that the experience of attending the clinic had been better than expected, this was significantly higher in the NIT arm (65% SOC vs 90% NIT for men; p=0.0001 and 65% SOC vs 92% NIT for women; p=0.0002). Furthermore, those patients randomly assigned to NIT were also more likely to disagree that they were in clinic for longer than expected (31% SOC vs 69% NIT for men; p<0.0001 and 46% SOC vs 69% NIT for women; p=0.01). Most patients undergoing NIT found the tests less uncomfortable than those in the SOC arm (51% SOC vs 70% NIT for men; p=0.04 and 57% SOC vs 80% NIT for women; p=0.0002). Finally, more male patients randomly assigned to SOC agreed that there were some things about their care that could be improved (28% SOC vs 13% NIT; p=0.0002).

Table 3

Satisfaction survey data

Chlamydia (n=32) was the most common STI detected (table 4). Following a positive result for chlamydia, four of the 32 patients did not attend clinic for further follow-up and did not receive treatment. In addition, five of the eight patients with an inhibitory chlamydia result did not attend for repeat testing. All seven of the NIT patients with a positive gonorrhoea NAAT had a subsequent negative result by culture, but seven of the 11 patients with an inhibitory gonorrhoea NAAT did not return for repeat testing. Three attempts by phone or letter were made to contact those who defaulted from follow-up with a positive or equivocal test result, and either the general practitioner was informed or responsibility left with the patient if diagnosis had been communicated. Participants within the SOC arm were more likely to decline HIV and syphilis testing.

Table 4

Results from the STI screening


Our trial demonstrates that NIT is a potentially efficient method of screening for STI in asymptomatic patients. We found the total time spent in the clinic was significantly reduced with NIT compared with SOC for both male and female patients (26 min vs 41 min for men and 23 min vs 45 min for women, respectively, p<0.0001). Most of this reduction in the NIT arm was due to the more rapid movement of patients through the clinic and the consultation and screening time were only modestly reduced. Participants in the SOC arm were also more likely to decline blood tests for HIV and syphilis, which may reflect having to wait for a different member of staff to perform venepuncture, whereas a single member of staff performed all tests within the NIT arm.

NIT for STI also appears to be highly acceptable to patients. Significantly more patients in the NIT arm than the SOC arm stated that the overall clinic experience had been better than expected (men 90% vs 65%, respectively; p=0.0001) and tests were less uncomfortable than expected (women 80% vs 57%; p=0.0002, men 70% vs 51%, respectively; p=0.04). There was no evidence that male patients who had previously attended for an STI check rated NIT more favourably than those who had no previous experience of the clinic (data not shown). When the analysis of times and satisfaction survey is stratified by age (≤24, >24 years) there were no differences between the treatment arms for either male or female patients.

A small number of other STI were identified within the SOC arm, which were not screened for within the NIT arm—T vaginalis, non-specific urethritis and genital warts. These are therefore likely to have remained undiagnosed had these patients been randomly assigned to the NIT arm of the study. Equally, the long-term consequences of these conditions in asymptomatic individuals remains uncertain,5 and UK national guidelines do not recommend the screening of asymptomatic individuals.6 NAAT testing for T vaginalis (Aptima Combo 2; Gen-Probe, USA)7 will be available in the near future, although it is not yet clear how it should be utilised. STI diagnosis in each arm was a secondary outcome of the study, and it was not possible to recruit enough patients to power the trial on this endpoint. The significance of the lack of difference in STI diagnostic rates between the NIT and SOC arms of the trial therefore remains uncertain.

Previous studies have assessed the sensitivity and specificity of NAAT for chlamydia and gonorrhoea8 but few have reported the impact on clinical services. Two retrospective reviews on the implementation of NIT9 10 did not have comparator arms and did not measure the impact on patient time spent in the clinic. They identified a small number of diagnoses that were initially missed using NAAT, but the lack of a comparator arm makes it difficult to draw firm conclusions. Both studies concluded that NIT was time saving and recommended its use to improve clinic efficiency.

Patient satisfaction with overall sexual healthcare provision has been measured in a number of studies11 but little has been reported specifically in those undergoing NIT. Previous reviews have suggested that NIT is acceptable based on high levels of service uptake,12 13 but other factors are also likely to contribute to attendance rates, including location and timing of the service. Wayal et al14 used a questionnaire-based survey from 274 men who have sex with men to determine the acceptability of self-taken oral and rectal swabs. Acceptability was reported to be high but no comparison was made with clinician-taken samples. A satisfaction survey was specifically designed for our study, but there is a need for a standardised measure to ensure that repeat surveys in different settings can be compared.15

The strengths of the study were the randomised controlled design performed in a large population of STI clinic attendees. Of the 1303 patients approached to enter the study, only 391 patients were randomly assigned although the majority of patients not entered into the trial were not eligible because they were symptomatic. The determination of symptoms was performed using a self-assessment triage questionnaire, which may not always be reliable. A fuller assessment may require taking a brief sexual history in addition to the questionnaire, but patients do not always recognise the presence of STI symptoms even on direct enquiry. The results of the study may also not be generalisable to other clinics depending on the specific care pathways in use.

NIT for gonorrhoea using NAAT provides the opportunity to test for infection in community venues where rapid access to a laboratory is not available, although antimicrobial sensitivity testing is not possible in the absence of culture. The Roche PCR Amplicor used in the study has been reported to have a relatively high false positivity rate for gonorrhoea16 and none of the PCR-positive specimens in our study were confirmed on culture, although direct comparison with gonorrhoea culture may be of limited value because the sensitivity of culture has been reported to be as low as 70%.17 Inhibitory results for chlamydia and gonorrhoea were only found in female patients, reflecting earlier reports, although the exact mechanisms causing this are unclear.18 Alternative NAAT tests, such as the Aptima Combo 2, have a high sensitivity and specificity,8 and may provide fewer false-positive results while retaining high sensitivity.19

To be most effective, the introduction of NIT for STI needs to be combined with a review of service delivery, including an assessment of patient flow within the clinic to help identify bottlenecks and determine the most appropriate skill mix.20 The use of healthcare assistants, after appropriate training, to manage asymptomatic patients can reduce the need for additional qualified nursing and medical staff, while increasing capacity and reducing waiting times. Medical and nurse input can then be focused on seeing symptomatic or more complex patients.20 The use of NIT by more junior members of the clinical team can lead to a reduced length of time spent in the clinic for patients and is likely to be cost-effective.

In summary, we have demonstrated that NIT for the asymptomatic screening of STI is highly acceptable to patients and can help to reduce patient time spent in the clinic, but its impact is dependent on being integrated into appropriate care pathways.

Key messages

NIT for asymptomatic patients attending sexual health clinics:

  • Can reduce the time patients spend in clinic but only if combined with appropriate care pathways.

  • Is a highly acceptable alternative to examination and taking genital swabs.

  • Can be associated with increased acceptance rates for HIV testing.


The authors would like to thank Katrina Hood and Rebecca Newson for their assistance in recruiting patients for this study.


View Abstract


  • Funding This study was supported by Heart of Birmingham primary care trust.

  • Competing interests JDCR is an associate editor of Sexually Transmitted Infections.

  • Ethics approval This study was conducted with the approval of the Solihull Local Research Ethics Committee.

  • Contributors LB study design, study supervision, data collection, preparation of manuscript; SP study methodology, statistical analysis; NJI study methodology, statistical analysis; CMcD patient recruitment; JDCR study concept and design, study supervision, review of manuscript.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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