Epididymitis is not a major outcome in ClaSS

Pelham M Barton, Senior Lecturer in Mathematical Modelling,
August 13, 2007

Dear Editor,

While sharing Adams and colleagues’ concerns about the use of major outcomes averted, I should like to point out a factual error in their description[1] of the results from the ClaSS model[2]. The definition of major outcome used in that report, which appears in the text on page 107 and in the caption to Figure 18 on page 108 of the report[2] excludes epididymitis. The “seemingly perverse” result that screening males in addition to females is more cost-effective than screening females alone is therefore based on an outcome measure that does not include epididymitis. While it is true that the cost of epididymitis is included in the calculations, the result cited still holds even if the cost of epididymitis is removed. In the interests of further clarity, I should also like to point out that we only considered screening males in addition to females: we never considered screening males alone.


[1] Adams E J, Edmunds W J, Turner K M. Commentary on “The cost-effectiveness of opportunistic chlamydia screening in England”. Sex Transm Infect 2007;83:275.

[2] Low N, McCarthy A, Macleod J, et al. Epidemiological, social, diagnostic and economic evaluation of population screening for genital chlamydial infection. Health Technology Assessment, 2007. Report No. 11(8).

Conflict of Interest

None declared