Literature review > Issue 8 > Review on Sparks et al. 

The issue of defining optimal screening algorithms for those at a risk of STIs but not presenting to clinics, or for those who do not contact health services at all, is under continuing investigation [1].

A further question arises in relation to the possibility of identification of any reinfection with Chlamydia trachomatis and Neisseria gonorrhoeae in those previously diagnosed with this condition. This recurrence occurs often within a relatively short period after demonstrably successful treatment, particularly in those with untreated partners or who are otherwise at high risk. It is therefore advised that consideration be given to active re-screening of these groups [2]. The combination of nucleic acid amplification assays and self-collected patient samples makes this process less cumbersome and alternative strategies for re-screening using patient-collected and mailed specimens have been explored in a number of studies.

This paper describes the outcome of a randomized trial to assess the feasibility and acceptability of re-screening heterosexual men and women diagnosed earlier with either gonococcal or chlamydial infection. Patient preferences compared were for retesting by mailing self-collected samples or re-attendance at the STD clinic. The study was underpowered to reach a conclusion and most of those contacted preferred the clinic re-attendance option. However the authors concluded that the availability of the mail based choice increased the proportion of those successfully retested, and that wider use of this option was worth further investigation in a definitive study.

The authors raised some interesting points in relation to mail based re-screening, and other issues have been separately flagged regarding this option in other studies. Overall, only 24% of 297 patients for whom re-screening was initiated in this study were ultimately tested, and this "highlights the persisting difficulties" associated with all re-screening efforts. One such difficulty here was the 'inability to contact 42% of potential subjects' despite a minimum of 5 contact attempts by telephone or letter for each patient. Other studies in the USA also had similar overall response rates. Even after agreement to participate, in one study, 10% of mailed samples could not be successfully tested. A Danish study obtained a slightly higher initial response rate (30%) using GPs to recruit patients. The authors of this study speculated that the need for an initial GP visit or reluctance to participate in an STI survey may have contributed to low acceptance. Conversely the presence of symptoms, in half those responding, was seen as a motivating factor for enrolment. Once recruited however, the completion rate for providing a mailed sample in this cohort was very high, again suggesting a high acceptability in those who took up this option.

Other points raised in other studies include those of the optimal time to re-screen, cost, including cost of laboratory testing, legislative restrictions in some settings, a more likely compliance by the 'worried well' rather than those in higher risk groups, the limitations of screening in one site only (urethra) in homosexually active men who may have rectal infection, privacy issues and fear of sample use for additional purposes including drug screening.

One earlier study identified costs, excluding those of testing, of a mail-based program at about $US25.00 per returned sample. The study reported here does not provide cost estimates for the study but recall attempts were more intense in this study and thus probably more expensive. Others have suggested that "participation might increase if patients were educated at the time of visit …and agreed to be re-screened through the mail". This may also decrease costs associated with repeated contact attempts.

There is an increasing consensus that a screening/re-screening approach is beneficial in terms of prevention of certain STIs.

Screening programs for Chlamydia have been justified on the basis of cost effectiveness and their success has been based on a high uptake rate [3].

Re-screening programs will also be subjected to a rigorous cost-effectiveness analysis if funding is to be provided and maintained. The argument for active re-screening of those who have already tested positive is a cogent one and public health outcomes will be enhanced by the exploration of re-screening strategies, which can readily identify those at risk of reinfection. The data in this and other studies suggest that the patient-collected and mailed specimens option will provide the required benefit to a significant subset of a high-risk group.

References:

1. Fenton KA, Ward H. National Chlamydia screening programme in England: making progress. Sex Transm Infect 2004;80:331-333.

2. Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines. MMWR Morb Mortal Wkly Rep 2002;51(no RR-6):33.

3. LaMontagne DS, fenton KA, Randall S, Anderson S, Carter P. Establishing the National Chlamydia Screening Programme in England: results from the first full year of screening. Sex Transm Infect 2004;80:335-341.

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