2 question here really: background below (the example is a hypothetical
one)
1) can anybody point me in the direction of a source for a)the
prevalence of lung cancer in a 55yr old caucasian female, lived in the
UK all her life, who has smoked 10-20 cigs/day for 35 yrs and whose
younger sister (heavier smoker) has just had lung cancer diagnosed; and
b) the sensitivity and specificity of a plain cxr for diagnosing lung
cancer in such an individual (no known co-existing lung diseases)?
2) i'd be very interested to know what peoples' best guesses are for
these values, if other people want to play this game then they could
e-mail me privately and if i get more than 10 responses say i'll put the
results up on the list. if any radiologists reply i'd be interested if
they could identify themselves as such (do they over or under estimate
the accuracy of the cxr i wonder)
background:
on the gp-uk list we've been discussing the relative merits of
performing a cxr at the request of the individual in a) above, and there
were of course pros and antis. we calculated predictive values, false
positive rates etc using a range of values for the variables mentioned
in a) and b) and the results were extremely interesting and i think have
surprised many. it has been suggested that we attempt to formalise the
results a bit by using some values that have a better basis in evidence
if possible.
I have searched Bandolier, the effective health bulletin and performed
some searches using Pubmed: suffice to say that i am aware of the trials
showing a failure of screening smokers to reduce lung cancer mortality;
and seen a snippet in a review by Eddy D that was difficult to interpret
(quote: Mayo Lung Project: Chest roentgenograms and sputum cytology lead
to false-positive test results in smokers of approximately 5% and 0.5%,
respectively. Because of the lack of evidence of benefit and because of
its potential harms and costs, screening for lung cancer is not
recommended). However i am drawing a blank on the questions above.
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