Chlamydia, Screening, Ireland
Genital Chlamydia trachomatis (CT) infection is the most common curable, bacterial sexually transmitted infection (STI) worldwide [1, 2]. The number of cases notified in Ireland increased from 3,353 in 2005 to 5,781 in 2009 . Notifications have increased since 2004 when legislation requiring laboratory notification came into effect. Chlamydia is usually a ‘silent’ asymptomatic infection, spread without the knowledge of those transmitting and contracting it: most cases remain undetected and thus untreated. It is a major public health problem because it causes pelvic inflammatory disease (PID) in up to 30% of infected women who are not treated, which can lead to ectopic pregnancy and tubal factor infertility, and it also facilitates the transmission of HIV in both women and men [1, 4].
Prevalence studies in Ireland have detected chlamydia in 4–11% of young people [5, 6, 7], with positivity rates of over 10% in some settings . Similar rates have been found in large studies in the United Kingdom (UK) , elsewhere in Europe  and North America . A 2004 review estimated UK rates of 4–5% for women under 20 years in the general population, and 8–17% in women under 20 years attending sexual health services . The authors of the review assumed, in the absence of data, that males had similar rates. Age under 25 years is considered a risk factor for infection in England . In the English National Chlamydia Screening Programme (NCSP) overall chlamydia positivity rates have averaged 7.6% in men and 9.3% in women, based on a total of 370,012 screening tests reported .
Chlamydia screening has become more feasible due to the development of urinebased laboratory tests, which can be used in clinical and non-clinical settings, instead of more invasive and uncomfortable methods such as endocervical and urethral swabs. Urine testing is now the norm for screening men for chlamydia. For these reasons and because most cases are asymptomatic and undetected, especially in women, several countries have introduced chlamydia screening interventions .
A 2005 report prepared by the Health Protection Surveillance Centre (HPSC)  concluded that an investigation of the feasibility, acceptability and likely uptake of chlamydia screening in various settings in Ireland should be prioritised. It also concluded that agreement on best practice for the management of identified infections and partner notification was urgently needed. Following a competitive tendering process in late 2006, the HPSC, supported by the Health Research Board (HRB), contracted a team of population health and other specialists from the Royal College of Surgeons in Ireland (RCSI), the National University of Ireland Galway (NUIG) and the Health Service Executive (HSE) to conduct a pilot study of chlamydia screening.The study ran from 2007 to 2009.
Since 2009, several articles and reports have been published internationally, including reviews and the results of screening studies, which question the case for chlamydia screening in the general population. A systematic review of screening programmes concluded that the available evidence did not justify the establishment of opportunistic chlamydia screening programmes in under-25 year olds in the general population, given methodological weaknesses in the trials cited as justification for screening .
A review of the three phases of the English National Chlamydia Screening Programme (NCSP) reported screening coverage levels in the target population of only 4.8% in 2007–2008 ; although by 2009–2010, 47% of sexually active young women and 25% of men had been tested . A review by the English National Audit Office  concluded that the NCSP had not demonstrated value for money, citing lack of efficiencies in purchasing and logistics. Also, models had shown that annual testing rates of young people of between 26% and 43% would be needed in order to significantly reduce the prevalence of chlamydia . The recent higher coverage levels achieved by the NCSP in reaching these recommended levels is a cause for optimism, and valuable lessons will be learned from the English national programme.
However, the potential of opportunistic chlamydia screening to prevent serious morbidity (chiefly pelvic inflammatory disease in women) has been challenged by the results of an important randomised control trial of screening among young female students in London . The trial found that most episodes of PID (30 of 38) would not have been prevented by annual screening as they occurred in women who had tested negative for chlamydia at the start of the 12 months.
Epidemiology | International Public Health
Balfe M, Brugha R, O'Connell E, Vaughan D, O'Donovan D, Coleman C, Conroy R, Cormican M, Fitzgerald M, Fleming C, McGee H, Murphy A, Ni Fhoghlu, O'Neill C, Gillespie P. Chlamydia Screening in Ireland: a pilot study of opportunistic screening for genital Chlamydia trachomatis infection in Ireland (2007-2009). Summary Integrated Report. Dublin: Health Protection Surveillance Centre (HPSC) Ireland and Health research Board (HRB) Ireland, 2012.