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Public health issues

Intro

The public health impact of chlamydial infections comprises the direct and indirect costs of chlamydial disease including mental as well as physical and economic costs. This 'cost of illness' crucially depends on the prevalence of the disease, the associated costs of detection, treatment and management and the impact on productivity [Malek & Malik, 1999].  Crucial to further research is cost benefit analysis of alternative strategies for detecting and managing chlamydial infections.

Prevalence and incidence

C. trachomatis is the most common sexually transmitted pathogen of humans, with an estimated 89 million new cases occurring world wide each year [Gerbase et al., 1998].  In the US, the incidence of new cases of chlamydial genital tract infection is approximately 4 million a year. This is almost certainly an underestimate because of underutilisation of the most sensitive diagnostic methods and because men are less likely to be screened for infection than women [Schachter, 1999].  In Europe there are an estimated 10 million new cases of chlamydial genital tract infection per year [Malek & Malik, 1999] with the prevalence of C. trachomatis infection in unscreened asymptomatic women ranging from 1.7 - 17% depending upon the setting, context and country [Wilson et al., 2002].  Prevalence rates vary widely according to age, gender, geographic region, social and cultural mores, risk factors and diagnostic methodology. For examples of prevalence observed in different geographic regions see the reviews of laboratory diagnostic tests.  Typically in developed countries the prevalence of genital chlamydial infection in sexually active women age 15 to 25 years old will be of the order of 9%, perhaps a little less for males. The risk factors are generally well known and include the age of sexual debut, the number of sexual partners, the frequency of sexual encounters and failure to use barrier contraception. The prevalence of infection may be much higher in developing countries or in selected population groups, such as women seeking termination of pregnancy. The prevalence of infection declines substantially with age in persons age 25 or more, an important consideration for public health strategy. Unfortunately some of the serious sequelae of chlamydial infection in women, such as tubal factor infertility, may persist for life.

Repeat or recurrent infection

The public health benefit of screening may be reduced by high chlamydia incidence and repeat infection rates.  Rieetmeijer et al., 2002 in Denver, Colorado did a retrospective cohort study of 3568 patients who were tested on multiple occasions. Of these, 491 (13.8%) had positive test results at their first visit (baseline infections), and 385 (10.8%) had positive results at a subsequent visit (incident infections). The overall incidence was 11.7 per 100 person-years of follow-up evaluation. Among those 25 years of age or younger the corresponding incidence was 19.7 per 100 person years. The incidence of new infections among persons without a baseline infection was 10.0 per 100 person-years, whereas the incidence of repeat infections was 23.6 per 100 person-years. Repeat infections accounted for 26% of all incident infections. The factors associated with repeat infection were younger age, non-use of condoms, and no treatment after contact with a partner who had a diagnosis of chlamydia or a chlamydia-related condition, as measured at the initial visit. Chlamydial infections in the community are dynamic. In a home-based setting in Denmark, Kjaer et al., 2000 found that the cumulative recurrence of urogenital C. trachomatis infections after antibiotic treatment was 29% over a 24 week period, presumably by reinfection from sexual partners. Effective screening strategy ideally requires rapid diagnosis and treatment, good sexual partner management and rescreening to ensure reinfection has not occurred.

The burden of chlamydial genital tract infection

The burden of chlamydial genital tract infections for health services and individuals is enormous, with women particularly disadvantaged. For example; there are roughly 1 million cases of pelvic inflammatory disease in women in the US each year leading to approximately 150,000 to 200,000 becoming involuntarily infertile as a result of bilateral obstruction of the fallopian tubes. At least a quarter of these cases for the US can be attributed to chlamydial infection [Westrom et al., 1992] while in the UK the figure is probably nearer 50%  [Bevan et al., 1995]. In the US in 1990 the direct costs of treating pelvic inflammatory disease and its complications were estimated at $2.18 billion plus indirect costs of $1.5 billion, a total cost of $4.2 billion. Private insurance met 41% of the direct cost and public payment sources about 30% [Washington et  al, 1990; 1987]. Projected costs for the year 2000 [Washington et al., 1991] were $10 billion, with an increasing proportion burdening public institutions. Most of this cost (79%) was related to the management of infection and its complications in women. Indeed these costs may be an underestimate because: a) the authors used the lower range of estimates for the direct healthcare costs of managing chlamydial infections and costs excluded included those for: b) complications in men, such as reactive arthritis; c) paediatric costs associated with adverse pregnancy outcome and child mortality; c) complications arising from asymptomatic or undiagnosed chlamydial infection. Psychosocial costs of chlamydial infection to patients and their partners are hard to estimate and were also excluded.

The studies of Washington et al., 1987; 1990; 1991 for the US are in many ways landmark studies. Comparable studies for the European or other regions as a whole have not been published. Nevertheless estimates of chlamydial related health costs for Sweden [WHO, 1990; Genc & Mardh, 1996] and for Finland [Paavonen et al., 1998] indicate that the burden of chlamydial infections on European health systems is comparable to that in the US. The key public health question therefore is what is the most effective strategy for detecting, managing and, if possible, preventing chlamydial infections and their complications. This is considered in the following series of web pages.

[MEW] July 2004

NEXT: Screening in Males

References

Bevan, C. D., Johal, B. J., Mumtaz, G., Ridgway, G. L. & Siddle, N. C. (1995). Clinical, laparoscopic and microbiological findings in acute salpingitis: report on a United Kingdom cohort. British Journal of Obstetrics and Gynaecology 102, 407 - 414.

Genc, M. & Mardh, P. A. (1996). A cost-effectiveness analysis of screening and treatment for Chlamydia trachomatis infection in asymptomatic women. Annals of Internal Medicine 124, 1 - 7. Full article html [Spreadsheet-based Bayesian decision analysis model. No sensitivity analysis and assumes 100% treatment success].

Kjaer, H. O., Dimcevski, G., Hoff, G., Olesen, F. & Ostergaard, L. (2000). Recurrence of urogenital Chlamydia trachomatis infection evaluated by mailed samples obtained at home: 24 weeks' prospective follow up study. Sexually Transmitted Infections 76, 169 - 172.

Malek, M. & Malik, F. (2001). Economic implications of Chlamydia trachomatis. In: International handbook of Chlamydia [ed. Moss, T. R.] pp 97 - 113. Euromed Publications Ltd., Haslemere UK, ISBN 1 899015 43 4 [Good review].

Paavonen, J., Puolakkainen, M., Paukku, M. & Sintonen, H. (1998). Cost-benefit analysis of first-void urine Chlamydia trachomatis screening program. Obstetrics and Gynecology 92, 292 - 298. Full article (html)

Rietmeijer, C. A., van Bemmelen, R., Judson, F. N. & Douglas, J. M. Jr. (2002). Incidence and repeat infection rates of Chlamydia trachomatis among male and female patients in an STD clinic: implications for screening and rescreening. Sexually Transmitted Diseases 29, 65 - 72.

Schachter, J. (1999). Infection and disease epidemiology. In: (Stephens, R. S. ed.,) Chlamydia: Intracellular biology, pathogenesis and immunity. Pages 139 - 169.  American Society of Microbiology Press, Washington D.C., ISBN 1-55581-155-8.

Washington, A. E., Aral, S. O., Wolner-Hanssen, P., Grimes, D. A.. &  Holmes, K. K. (1990). Assessing risk for pelvic inflammatory disease and its sequelae. Journal of the American Medical Association (JAMA) 266, 2581 - 2586.

Washington, A. E., Johnson, R. E. & Sanders, L. L. (1987). Chlamydia trachomatis infections in the United States. What are they costing us? Journal of the American Medical Association (JAMA) 257, 2070 - 20722.

Washington, A. E. & Katz, P. (1991). Cost of and payment source for pelvic inflammatory disease. Trends and projections, 1983 through 2000. JAMA 266, 2565 - 2569.

Westrom, L. R., Joesoef, R., Reynolds, G., Hagdu, A. & Thompson, S. E. (1992). Pelvic inflammatory disease and fertility. A cohort study of 1,844 women with laparoscopically verified disease and 657 control women with normal laparoscopic results. Sexually Transmitted Diseases 19, 185 - 192. 

WHO Regional Office for Europe (1990). Annexes 1 and 2. Cost estimates of infections and of salpingitis due to C. trachomatis, based in Swedish figures. In: Guidelines for the prevention of genital chlamydial infections [Ed. Mardh, P. A.] pp 38 - 42. WHO collaborating centre for STD, Uppsala.

Wilson, J. S., Honey, E., Templeton, A., Paavonen, J., Mardh, P. A. & Stray-Pedersen, B. (2002). A systematic review of the prevalence of Chlamydia trachomatis among European women. Human Reproduction Update. 8, 385 - 94.