As the Department of Health comes under criticism again for its approach to Chlamydia screening at the local level,1,2 there are calls to nationalise the initiative and increase the number of sexually active people in the 14–25 age group tested in order to reach the high volume of testing required to reduce the prevalence of Chlamydia in this high-risk population.2 An increase in testing will obviously have an impact on local laboratory workloads and, as with any clinical investigation, the quality of patient samples is important in order to achieve maximum sensitivity and reliability of the nucleic acid amplification tests used for the identification of Chlamydia. This article explores some of the sampling devices and vessels available to healthcare professionals in the UK and how they can enhance the performance of Chlamydia screening programmes.
Chlamydia in young people
Genital infection with Chlamydia trachomatis is the most commonly diagnosed bacterial sexually transmitted infection (STI) in the UK and its incidence continues to increase, especially in young people under the age of 25.3 However, infection is easy to detect and treat with antibiotics.
One in 14 young people tested has been found to carry Chlamydia. Although Chlamydia infection is asymptomatic in most (up to 70%4) of carriers, if left untreated it can lead to serious health complications such as infertility, ectopic pregnancy and pelvic pain in women, and to urethritis and epidydimitis in men. It is also associated with arthritis in both sexes. This is why it is important to screen the high-risk group for Chlamydia.
Those most at risk of infection are men and women under the age of 25, especially if they have had a new sexual partner in the past 12 months; those who do not use barrier contraception; and women who are undergoing termination of pregnancy.
In 2003, the National Chlamydia Screening Programme (NCSP) was launched in the UK with the aim of controlling Chlamydia through the early detection and treatment of asymptomatic infection, preventing the development of sequelae and reducing onward disease transmission in young people under the age of 25. However, over six years on, testing levels in this population group are not yet high enough to reduce the prevalence of Chlamydia significantly.2
The NCSP recommends that sexually active young people between the ages of 14 and 25 should be tested for Chlamydia annually.
Sampling recommendations
Guidelines for the screening of patients for Chlamydia, including the collection of samples, are available for consultation and local adaptation.4
Patients can provide their own samples for testing in many local initiatives. For women, the easiest sample to provide is a first void urine specimen but they can also provide a self-taken vaginal swab. Individual trusts provide patients with instructions for the collection of high vaginal swabs. Alternatively, in women undergoing a vaginal examination, health professionals can take an endocervical swab specimen. In this instance, it is recommended to remove excess mucous or discharge, to insert the swab into the opening of the cervix and to firmly rotate the swab against the endocervix.
For men, a first void urine (held in the bladder for at least 1-2 hours) specimen is recommended.
Samples are then tested using a nucleic acid amplification test.
Urine collection
Urine collection is the most simple and least invasive method of specimen collection for Chlamydia testing, for both men and women. Nevertheless, it is important that the vessel used is of high quality, meeting requirements for the safe transport of biological samples.
The Sterilin 30-mL universal container (Fig 1) is ideal for the collection of urine samples for Chlamydia testing. The special flow-seal cap prevents leakage (leak tested according to the European Standard BS EN 14254:2004 Annex D), ensuring safe and problem-free transport of samples to the laboratory. The containers can also withstand 95 kPa (one bar) of pressure, ensuring it meets IATA regulations for diagnostic and infectious sample shipments.
The universal containers are free-standing with a conical base and thick-walled construction, which is ideal for centrifugation. They are aseptically manufactured from virgin polystyrene under cleanroom conditions (Class 7 ISO 14644) to exclude the possibility of microbiological contamination, thus ensuring accurate and reliable results.
Vaginal/endocervical swab collection
The Copan universal transport medium collection kit with the regular flocked swab (available from Sterilin) is ideal for the collection and transport of vaginal and endocervical swab specimens for Chlamydia testing by nucleic acid amplification tests.
The kit is free from enzymes and inhibitors that may interfere with nucleic acid amplification assays and the liquid transport medium includes antibiotics to prevent overgrowth of background bacterial and fungal flora. Furthermore, the design of the Copan flocked swab ensures efficient sampling of the clinical site, followed by optimal release of the specimen into the universal transport medium.
Traditional rayon or Dacron swabs consist of a compact fibre matrix wound onto a plain wooden, plastic or metal shaft. The winding process determines the shape of the swab tip. This network of interwoven fibres absorbs the patient sample but, when it is placed in the transport medium, a large proportion of the sample is trapped in the fibre matrix rather than being released into the surrounding medium, which can be highly detrimental to the performance of subsequent test methods.
In contrast, the Copan flocked swab has a moulded plastic shaft and tip that can be designed in almost any shape to optimise the collection of samples from specific body sites. Standard Copan flocked swabs (Fig 2) are generally used for vaginal and endocervical specimen collection; however, an endocervical flocked swab (Fig 2) is also available for use in the clinical setting, if preferred.
The plastic tip base is electrostatically coated with high-density perpendicular nylon fibres to produce a flocked pile (Fig 3). This brush-like structure permits the efficient removal of the sample from the body surface and the uptake of liquid through capillary action. The flocked pile is only about 1 mm deep, which allows the sample to remain close to the surface of the swab at all times and enables efficient sample release. This is further facilitated by the inclusion of glass beads in the Universal transport medium tube. Tests have shown that the flocked swab releases over 95% of the sample collected, compared to 25% from a standard fibre-tipped swab.
In a recent comparison between the use of the Copan flocked swab Universal transport medium system and a traditional rayon swab system in the detection of Chlamydia using a nucleic acid amplification method, the flocked swab system demonstrated improved amplification efficiency and increased sensitivity, which the authors concluded was probably due to the quantity of sample collected with, and released by, the flocked swab.5
Quality and reliability
As an established leader in single-use laboratory plastics, the Sterilin brand has been setting world standards for quality, reliability and user safety for more than 40 years.
Sterilin offers a range of over a thousand products for the clinical and healthcare sectors, from universal containers and Petri dishes to pipettes and mucus extractors. In addition, Sterilin is the exclusive distributor for the Copan range of swabs.
Copan is the worldwide market leader in the provision of high-quality added-value solutions for sample collection, preservation and transport. Identifying the critical importance of the pre-analytical, sample collection process, it has developed the innovative patented Copan flocked swab range.
References
1 National Audit Office. Young people’s sexual health: the National Chlamydia Screening Programme. London: NAO, 2009.
2 UK Parliament Committee of Public Accounts. Young people's sexual health: the National Chlamydia Screening Programme. 7th Report, Session 2009–10.
3 Department of Health. National Chlamydia Screening Programme Core Requirements (3rd edn). London: DH, 2006 (www.dh.gov.uk/PolicyAndGuidance/HealthAndSocialCareTopics/SexualHealth/SexualHealthGeneralInformation/SexualHealthGeneralArticle/fs/en?CONTENT_ID=4084098&chk=CSLxsK).
4 Health Protection Agency Primary Care Unit and GP Microbiology Laboratory Use Group. Diagnosis of Chlamydia: quick reference guide for general practices. London: HPA, 2008 (www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1194947422721).
5 Milia MG, Dal Conte I, Gregori G et al. Comparison between UTM-RT and M4RT kits for the collection of clinical specimens for the detection of Chlamydia trachomatis with the cobas TaqMan 48 CT test (Abstract). 19th European Congress of Clinical Microbiology and Infectious Diseases. Helsinki, Finland, 2009.