Is Europe ready for STD screening?

Is screening cost beneficial as a strategy to combat the epidemic of genital chlamydial infections and some other sexually transmitted diseases (STDs)? What are the medical, human, and social benefits and costs of screening? Finally, are we ready to start a programme of more general screening of STD agents within the populations of Europe? There are a number of reasons to screen for Chlamydia trachomatis. At least half of infected people are carriers-that is, they either do not experience sufficient symptoms to feel motivated to consult, or they simply have no symptoms at all. Screening and identifying such cases allows detection of additional chlamydia positive cases through partner notification. This is highly rewarding as more than half of all partners of a chlamydia infected index case are also likely to be infected. ' This is true even when less sensitive detection methods, such as ELISA (enzyme linked immunosorbent assay) are used. Another important reason to screen is that adverse immunological reactions may be induced by chlamydial infections such as production of chlamydial heat shock protein (HSP) antibodies, which cross react with human HSP. Such adverse immune reactions might not be abolished by eradicating the organism by antibiotic therapy; thus, breaking the transmission chains by detection and treatment of carriers is important. The overall effect of reducing the number of chlamydial infections can be demonstrated by analysis of the situation in Sweden (a country where the notification of infections by Chlamydia trachomatis has been obligatory since 1982), where the number of reported cases has dropped from approximately 40 000 cases in 1987 to around 15 000 cases in 1994.2 The introduction of more sensitive diagnostic techniques, PCR (polymerase chain reaction) and LCR (ligase chain reaction), in the most recent years resulted in only a marginal increase in reported chlamydial infections. Furthermore, there has recently been increased screening for C trachomatis among Swedish men. Along with this drop in prevalence there has been a corresponding reduction in the number of cases of pelvic inflammatory disease (PID)3 and of ectopic pregnancies,4 two of the known complications of genital chlamydial infections. A drop in prevalence has also been seen in parts of the USA which have instigated screening programmes for genital chlamydial infection.5 Whether or not there has been or will be a similar drop in the number of cases of infertility in these places, is, however, not yet known. Among the obstacles to the introduction of wider STD screening in Europe is, of course, the current critical situation of health economics, particularly in eastern Europe. The message that a society may gain and not lose money in the long run6 7 -that is, in a perspective of a decade, by screening for, for example, C trachomatis, may not be immediately attractive to those responsible for the management of healthcare budgets, particularly budgets that rely on government money. New expenditure is seldom sanctioned for benefits that are discounted over such a time perspective. In this context it is necessary to realise that the mean time lag that passes after a primary tubal chlamydial infection and before a woman attends because of PID or ectopic pregnancy is approximately 7-8 years. These two conditions are costly to society. Abdominal pain in PID is likely to result in an increased consumption of health care and pain relieving drugs etc, adding costs to the health budget. Many social costs due to STDs, their complications, and sequelae have not generally been considered in cost-benefit calculations; costs which may exceed several fold the costs of detection and treatment of the original condition. It has been calculated that it is cost beneficial to screen for C trachomatis when the prevalence of genital chlamydial infection is approximately 6%6 and when treating all detected cases with 1 g of azithromycin as a single dose (assuming a non-existent compliance problem if the drug is given at a clinic). In another study8, which used different criteria for diagnosing PID, included an estimate of the number of silent PIDs, and used other methods for detecting chlamydia infection, a prevalence of 3% was found to be the cut off for screening shown to be cost beneficial. In 24 family planning clinics in 14 European countries, we found the prevalence of C trachomatis infections in 3000 women aged 15 to 45 years, who considered themselves to be gynaecologically healthy, to range from 00% to 7.6%. 2 The study made use of a PCR method for testing urine samples. In five of these countries, the prevalences were above 3%. Selective screening is likely to increase the cost-benefit rates in populations with overall prevalences below the threshold for gain. Thus, screening of cohorts ofwomen with known risk factors for infection or symptomatic cases-for example, women complaining of vaginal discharge, is likely to identify even higher prevalences than in asymptomatic cohorts. Furthermore, if partner notification is undertaken among the sexual partner(s) of individuals found positive at screening and also of the partner's partner(s), such case detection is likely to increase the cost-benefit further. Which methods should be used for screening? The method used must be suitable for its Institute of Clinical Bacteriology, Uppsala University, Uppsala, Sweden P-A MArdh