Very interesting example from Dr Padmanabhan Badrinath; and glad to know
the design of Amarti's study.
Observational studies such as case-ctrl studies may be more vulnerable
to selective publication, because of potentially wider difference in
results from similar studies; plus, because of relatively easy to
conduct a case-ctrl study (and therefore easy to give up result without
publication). Consequently, only 'positive' results published and the
correlation between factors is over-estimated.
Arturo may have a search of literature and see how many studies (trials,
observational studies) have been published on the topic. If well
designed clinical trials are already available, it may need to justify
why this case-ctrl study being conducted. If only observational studies
are available and if these studies show mainly 'positive' result, the
risk of publication bias should be assessed, eg, using funnel plot. If
your case-ctrl study is well designed and important confounders
adjusted, your 'negative' result should be published, to warn readers
about potential problem of publication bias on the topic. So your
'negative' result may contribute 'positively'.
-----------------------------------------
Fujian Song
NHS Centre for Reviews and Dissemination
University of York
York, UK
-----------------------------------------
Arturo Marti-Carvajal wrote:
>
> Dear all:
>
> This discussion interesting restitution is been.
> Our research is a study of cases and controls based in patient hospital on
> the relationship between iron deficiency and prematurity in a not developed
> country. Would somebody like to see the abstract?
>
> Many thanks in advance,
>
> Arturo
>
> At 20:25 12/01/99 PST, you wrote:
> >Dear all,
> >I have been following the recent discussion on the acceptence/rejection
> >of negative trials (the question raised by Arturo Marti-Carvajal).
> >Fujian Song from York mentions that negative results are more likely to
> >be accepted if they are likely to change current practice or question
> >long-held clinical doctrines. I would like to add that this is not
> >restricted to clinical trials and even observational studies could
> >produce a similar results as shown by the case control study published
> >in the recent issue of Annals of Internal Medicine on the role of
> >antibiotic prophylaxis to prevent infective endocarditis in cardiac
> >patients.
> >Strom BL, Abrutyn E, Berlin JA et al. Dental and cardiac risk factors
> >for infective endocarditis. A population based case control study. Ann
> >Intern Med 1998;129:761-769.
> >
> >I have taken the liberty of reproducing the jist of the article from our
> >JSCAN (a monthly newsletter summarising all important studies which will
> >have impact on patient care circulated to primary and secondary care
> >physicians in our Health District, compiled by me)
> >----------------------------------------------------------------------
> >In this era of evidence based medicine (EBM), long-held clinical
> >doctrines are being questioned. Readers may well remember the medical
> >school teaching that antibiotic prophylaxis should be given to risk
> >groups before dental procedures to prevent infective endocarditis. This
> >is still the current teaching, though its effectiveness in humans has
> >not been proven. The risk group for prophylaxis include those with
> >cardiac valve abnormalities. This case control study from Philadelphia
> >questions the value of antibiotic prophylaxis in patients with valvular
> >abnormalities. The authors interviewed 273 patients with
> >community-acquired infective endocarditis and matched neighborhood
> >controls. Information on demographic variables, host risk factors, and
> >dental treatment was obtained from medical records and the interview.
> >There was no difference in the frequency of dental treatment between
> >cases and neighborhood controls in the preceding three months. 38% of
> >the cases knew of their cardiac lesions as compared to 6% of the
> >controls. Of the cases and controls who knew of their condition, 20.2%
> >of cases and 23.5% controls had had dental treatment over the last two
> >months. Case patients more often had a history of mitral valve prolapse,
> >congenital heart disease, cardiac valvular surgery, rheumatic fever and
> >heart murmur without other known cardiac abnormalities. The authors
> >concluded that dental treatment might not be a risk factor for infective
> >endocarditis, even in patients with valvular abnormalities, but that
> >cardiac valvular abnormalities are strong risk factors and that
> >physicians should reconsider the current policies for prophylaxis.
> >
> >The accompanying editorial puts this study into context and makes
> >practical recommendations; "The time has come to scale back on
> >prophylaxis against endocarditis before dental treatment. In the matrix
> >of procedures related to predisposing conditions, prophylaxis should be
> >downgraded to "not recommended" for most dental procedures except
> >extractions and gingival surgery (including implant placement) and for
> >most underlying cardiac conditions except prosthetic valves and previous
> >endocarditis".
> >----------------------------------------------------------------------
> >
> >I will be happy to hear from the list.
> >
> >Regards,
> >
> >Badri
> >
> >Dr.P.Badrinath M.D.,M.Phil.,(Epid) PhD(Cantab)
> >Assistant Professor and Epidemiologist,
> >Department of Community Medicine,
> >UAE University, PO Box 17666, Al Ain,
> >United Arab Emirates.
> >Tel: 00 971 3 5039 652
> >Fax: 00 971 3 672022.
> >[log in to unmask]
> >
> >
> >______________________________________________________
> >Get Your Private, Free Email at http://www.hotmail.com
> >
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