Urinary diagnosis of gonorrhoea and chlamydia in men in remote Aboriginal communities

Abstract

MJA 1997; 166: 468-471  

Introduction

Urine tests for the detection of gonorrhoea and chlamydia are now commercially available. Enzyme immunoassay (EIA) tests have sensitivities above 80% and specificities above 93%,^6-9 while polymerase chain reaction (PCR) tests have reported sensitivities of 90%-100% and specificities of 98%-100%.^10-14 These technologies offered exciting possibilities to address some of the difficulties in delivering STD services, so, after receiving approval from the Alice Springs Institutional Ethics Committee, the Tri-State STD/HIV Project (TSP), in collaboration with Nganampa Health Council (NHC) and the Central Australian Aboriginal Congress (CAAC), both organisations controlled by Aboriginal communities, undertook the programs described in this article.  

Methods

Phase I: NHC provides health services to several remote Aboriginal communities and conducts annual syphilis serology screening programs in these communities. NHC maintains a population register, and all persons between the ages of 12 and 40 years who are in the communities during the screening programs are sought out and asked to participate. In April 1995, 189 men participating in this program in three communities serviced by NHC were asked to give a first-void urine sample in addition to the blood sample for the syphilis test.

Phase II: In June 1995, another 218 men in the remaining three NHC communities had urine tests only; all males over the age of 12 who were present in the communities at the time were asked to participate.

Phase III: In October 1995, a further 53 men were tested who had not been previously tested.

Phase IV: CAAC, as part of its many functions, provides the health service to the Alice Springs Gaol. In June 1995, 33 new inmates were asked to give a first-void urine sample as part of their comprehensive health check on admission.

Diagnostic tests used for gonorrhoea were culture, EIA (Abbott Gonozyme, Chicago, IL) and PCR (Roche Amplicor CT/NG, Branchburg, NJ) and for chlamydia were EIA (SYVA MicroTrak II, Palo Alto, CA) and PCR (Roche Amplicor, Branchburg, NJ) (Box 1, below). If there was insufficient urine for all tests, the order of priority was to do PCR first, then culture, chlamydia EIA and finally gonococcal EIA. To check for cross-contamination between PCR specimens, all Phase III specimens that provided sufficient urine were divided before any PCR procedures were performed. When a positive result was obtained the other half of the original sample was retested.

Chocolate and/or Thayer-Martin agar plates incubated in candle jars or CO₂ gaspacks were used for gonococcal culture. BioCult GC tubes (Orion Diagnostica, Espoo, Finland), which contain a modified Thayer-Martin dipslide and a CO₂-generating tablet, were also trialled. Culture media were inoculated with sediment from 10 mL of centrifuged urine and incubated for up to 72 hours at 35^oC on-site and/or at Western Pathology in Alice Springs. Neisseria gonorrhoeae was identified by standard methods: typical morphology of colonies, oxidase paper test, microscopy with Gram stain, and latex agglutination (Phadebact GC, Boule Diagnostics AB, Huddinge, Sweden). Urine samples for EIA and PCR were prepared on-site according to the test manufacturer's specifications and then sent to Western Pathology in Alice Springs for processing.

Male Aboriginal health workers and registered nurses in each clinic were responsible for liaison with the community and collection of specimens. Each man was asked to give 25-40 mL of first-void urine in a sterile collection jar. No urethral swabs were sought. Initial preparation of urine specimens for transport to the laboratory was completed within three hours of collection. A diagnosis of infection was made and treatment was initiated if any test was positive. Resident clinic staff were responsible for offering treatment, further investigation and safe-sex education to infected men and their sexual partners.  

Results

Study population

The rate of infection

Treatment and follow-up

Performance of the tests used

During Phase III, 19 of the 20 initially positive PCR results were retested (in one case there was insufficient urine). In 18 of these cases there was complete agreement between the first and second test. One chlamydia-positive specimen was negative on the second testing. However, because of delays in transport, the tests on this specimen were done at six and eight days after collection, well in excess of the four days maximum recommended by the test manufacturers.  

Discussion

The variation in participation rates in different communities and age-groups was largely attributable to the numbers of people who happened to be present at the time of the study (people in these remote communities being highly mobile), the working relationship between community members and the health staff, and the assiduousness of the health staff in conducting the program. In central Australia it is often considered, without specific evidence, that people who do not participate in such programs may be at higher risk of infection. Recent work by NHC showed no difference in rates of syphilis infection between those tested during the main body of a screening program and those tested later as part of an effort to test non-participants (Dr Penny Miller, unpublished data).

The screening programs in our study were intended to identify the most effective and practical tests for everyday use in remote clinics. Collection of urethral swabs was avoided because it would not have been acceptable to the community. Hence, the study lacked a diagnostic "gold standard" and could not formally evaluate sensitivities and specificities. The published specificities of all the tests were high -- above 98% for urine PCR tests.^10-14 The procedures used in Phase III demonstrated no problems with cross-contamination in PCR testing. Several studies have suggested that urine PCR tests for chlamydia are more sensitive than urethral-swab culture and highly specific.^10-13 Less work has been done on urine PCR for diagnosing gonococcal infection, but two studies indicate sensitivities above 90% and specificities of 100%.^13,14

In ideal conditions, the sensitivities of urethral-swab microscopy and culture are 90%-98%,^15,16 but are likely to be much less in remote communities because of high staff turnover, the use of non-nutritive transport media, and frequently prolonged transport times. In such circumstances, urine PCR may be as good as or better than urethral-swab microscopy and culture for diagnosis of gonorrhoea. In any event, according to local management protocols,¹⁷ all men presenting to clinics with urethritis are offered immediate treatment for both gonorrhoea and chlamydia.

In terms of practical application, PCR was superior to culture for gonorrhoea and EIA for both infections. PCR tests detected more infections with either organism than did the other tests (Box 3). Assuming that the high published specificities for the PCR tests held under field conditions, this increased rate of detection would be attributable to a superior sensitivity. The PCR test was also the easiest to use: urine is simply stored and transported at 4¡-8¡C in the same jar used to collect it. The urine must then be processed in the laboratory within four days (test manufacturer's instructions), which is usually feasible in most remote situations. In contrast, both EIA tests used require centrifuging before transport, and the SYVA MicroTrak II EIA required addition of a transport buffer.

However, PCR tests do not provide information about antibiotic susceptibility. If PCR technology is to be used as the principal diagnostic tool for gonorrhoea, there would need to be accompanying sentinel systems for gonococcal culture and antibiotic susceptibility. We found that culture of first-void urine was positive in 72% of diagnoses of gonorrhoea. Sensitivities of 70%-100% for urine culture of gonorrhoea have been reported.^18,19 On this basis, urine culture in addition to urine PCR for diagnosis of gonorrhoea could be performed routinely at sentinel sites and during similar programs to those reported here in order to maintain antibiotic-sensitivity surveillance. In the field situation, the BioCult GC tubes detected more gonorrhoea than standard Thayer-Martin plates and were easier and more convenient to use.

The accuracy, ease of use and acceptability to men of urine PCR tests suggest several strategies to make clinical services more accessible to people, reduce the amount of disease in the community and identify individuals who are in need of safe-sex education. The use of urine tests for routine diagnosis may encourage more men to present with an STD, even if there is no male practitioner present. Health services could adopt active case-finding strategies such as opportunistic testing when people present for other reasons, including annual comprehensive health checks or community surveys. Such strategies are under consideration by health services in central Australia. For example, CAAC is seeking funding to establish an outreach program via a mobile clinic to make comprehensive well-men's check-ups, including STD checks, accessible to Aboriginal men in Alice Springs.

We also examined screening as an STD control strategy. With fewer than 10 men refusing to participate, these programs resulted in 88 men who had either gonorrhoea or chlamydia and at least 45 of their sexual partners being treated. We did not have the resources to determine whether the men were symptomatic at the time of the test. However, none of them had presented to the clinic for treatment. When these findings are considered in the light of routine notifications and our own local experience, it is likely that most of these people would not have been diagnosed and treated outside these programs. Health services catering to remote Aboriginal communities in other parts of Australia may wish to consider this new technology and its usefulness in comprehensive STD education and control programs.  

Acknowledgements

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(Received 24 June, accepted 17 Oct, 1996)