The best ever study on chlamydia screening does not support screening
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Randomised controlled trial of screening for Chlamydia trachomatis to prevent pelvic inflammatory disease: the POPI (prevention of pelvic infection) trial
The best ever study on chlamydia screening does not support screening
Many people ought to be congratulated for this study: Mainly
Oaketshott et al (1) for providing what is likely to be the defining
study on chlamydia screening and the natural history of chlamydia in women
but also the funders of the study for supporting research on chlamydia
screening when a national policy decision has already been taken to
implement it, the ethics committee for allowing a non-treatment group and
the BMJ for publishing a study with a negative result.
Thanks to all of them we now know that the incidence of PID is lower than
anticipated (1.3% in screened women compared with 1.9% in controls -
`relative risk 0.65, 95% confidence interval 0.34 to 1.22), that in the
population studied most PID occurred in screen negative women and that PID
often follows incident (new) chlamydia infection.
This large RCT (n=2529) used appropriate outcomes and had an impressive
follow up rate (94%) for inner city highly mobile women. It did not find a
statistically significant impact of chlamydia screening on PID incidence.
Unlike Oakeshott et al we believe that the study was not underpowered. The
reason why this excellent study could not find a statistically significant
reduction in PID incidence was that screening preventable PID was too rare
to make it an important public health problem, one of the basic
requirements for any screening programme.
To prevent chlamydial PID through screening it has to have a latent period
when chlamydia is present but has not caused PID. The study by Oakeshott
et al suggests that chlamydial PID often follows incident chlamydia
infection. If this would be correct screening could not reduce PID
incidence, unless by reducing the prevalence it would also reduce the
incidence of chlamydia infection. The latter still needs to be shown.
We are now able to calculate the health service costs for the prevention
of chlamydial PID through screening (of women). Findings by Kermec et al
(2) suggest that the lowest unit cost of a chlamydia screening test that
could be achieved in the UK National chlamydia Screening Programme (NCSP)
is £33. Oakeshott et al estimated that if chlamydia screening could reduce
the incidence of PID 147 women need to be screened to prevent one case of
PID. If screened through the NCSP this would cost at least £4851 per case
of PID prevented. Chlamydia screening could have other benefits than the
prevention of PID which could lower the costs per harmful outcome
prevented. One the other hand it has yet to be shown that screening men as
undertaken by the NCSP reduces the risk of PID or its consequences (3).
The cost of one episode of PID prevented through screening is thus
unlikely to be lower than for example the £4055 base tariff for the care
of people with “Non-Transient Stroke or Cerebrovascular Accident, Nervous
system infections or Encephalopathy” (4).
If screen preventable chlamydial PID is not a serious public health
problem, if there is no latent period, if an excellent RCT could not find
a statistically significant benefit from screening and more quality of
life could be achieved if the money is spend on something else then we
need to ask ourselves if there are not better options to improve the
sexual and reproductive health of young women than chlamydia screening.
Screening and “treatment” for unmet contraceptive needs may be an obvious
candidate.
References
1 Oakeschott P et al Randomised controlled trial of screening for
Chlamydia trachomatisto prevent pelvic inflammatory disease: the POPI
(prevention of pelvic infection) trial BMJ 2010;340:c1642
2 Kermec M, Grant A, Adams E. Current costs of Chlamydia screening in the
community using a top-down and bottom up approach. Poster presented at the
Second Joint Conference of the British HIV Association and the British
Association for Sexual Health and HIV, Manchester 20-23 April 2010,
Abstract P181 in HIV Medicine Vol 11, Suppl 1 May 2010
3 U.S. Preventive Services Task Force. Screening for chlamydial
infection: U.S. Preventive Services Task Force recommendation statement.
Ann Intern Med. 2007 Jul 17;147(2):128-34. Epub 2007 Jun 18.
Rapid Response:
The best ever study on chlamydia screening does not support screening
Many people ought to be congratulated for this study: Mainly
Oaketshott et al (1) for providing what is likely to be the defining
study on chlamydia screening and the natural history of chlamydia in women
but also the funders of the study for supporting research on chlamydia
screening when a national policy decision has already been taken to
implement it, the ethics committee for allowing a non-treatment group and
the BMJ for publishing a study with a negative result.
Thanks to all of them we now know that the incidence of PID is lower than
anticipated (1.3% in screened women compared with 1.9% in controls -
`relative risk 0.65, 95% confidence interval 0.34 to 1.22), that in the
population studied most PID occurred in screen negative women and that PID
often follows incident (new) chlamydia infection.
This large RCT (n=2529) used appropriate outcomes and had an impressive
follow up rate (94%) for inner city highly mobile women. It did not find a
statistically significant impact of chlamydia screening on PID incidence.
Unlike Oakeshott et al we believe that the study was not underpowered. The
reason why this excellent study could not find a statistically significant
reduction in PID incidence was that screening preventable PID was too rare
to make it an important public health problem, one of the basic
requirements for any screening programme.
To prevent chlamydial PID through screening it has to have a latent period
when chlamydia is present but has not caused PID. The study by Oakeshott
et al suggests that chlamydial PID often follows incident chlamydia
infection. If this would be correct screening could not reduce PID
incidence, unless by reducing the prevalence it would also reduce the
incidence of chlamydia infection. The latter still needs to be shown.
We are now able to calculate the health service costs for the prevention
of chlamydial PID through screening (of women). Findings by Kermec et al
(2) suggest that the lowest unit cost of a chlamydia screening test that
could be achieved in the UK National chlamydia Screening Programme (NCSP)
is £33. Oakeshott et al estimated that if chlamydia screening could reduce
the incidence of PID 147 women need to be screened to prevent one case of
PID. If screened through the NCSP this would cost at least £4851 per case
of PID prevented. Chlamydia screening could have other benefits than the
prevention of PID which could lower the costs per harmful outcome
prevented. One the other hand it has yet to be shown that screening men as
undertaken by the NCSP reduces the risk of PID or its consequences (3).
The cost of one episode of PID prevented through screening is thus
unlikely to be lower than for example the £4055 base tariff for the care
of people with “Non-Transient Stroke or Cerebrovascular Accident, Nervous
system infections or Encephalopathy” (4).
If screen preventable chlamydial PID is not a serious public health
problem, if there is no latent period, if an excellent RCT could not find
a statistically significant benefit from screening and more quality of
life could be achieved if the money is spend on something else then we
need to ask ourselves if there are not better options to improve the
sexual and reproductive health of young women than chlamydia screening.
Screening and “treatment” for unmet contraceptive needs may be an obvious
candidate.
References
1 Oakeschott P et al Randomised controlled trial of screening for
Chlamydia trachomatisto prevent pelvic inflammatory disease: the POPI
(prevention of pelvic infection) trial BMJ 2010;340:c1642
2 Kermec M, Grant A, Adams E. Current costs of Chlamydia screening in the
community using a top-down and bottom up approach. Poster presented at the
Second Joint Conference of the British HIV Association and the British
Association for Sexual Health and HIV, Manchester 20-23 April 2010,
Abstract P181 in HIV Medicine Vol 11, Suppl 1 May 2010
3 U.S. Preventive Services Task Force. Screening for chlamydial
infection: U.S. Preventive Services Task Force recommendation statement.
Ann Intern Med. 2007 Jul 17;147(2):128-34. Epub 2007 Jun 18.
4 Department of Health; Confirmation of Payment by Results (PbR)
arrangements for 2010-11
http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/@ps/documents/digitalasset/dh_115626.xls#'8.
OPCS 4 Adult Orthopaedic'!A1 accessed 3.5.10
Competing interests:
None declared
Competing interests: No competing interests