Dear Eleri/List,
Just a quick note on the summarising of diagnostic tests. You should read
the short paper by Lachs et al. (full OVID ref. below) which addresses
Dipstick testing for UTIs. The point that it makes, very elegantly, is that
the test performance varies depending on the pre-test probability. This
sounds unremarkablefor those used to dealing with PPV/NPV.
HOWEVER, this paper has evidence that the Sensitivity & Specificity vary
depending on the Pre-Test Probability. This has serious implications for
the application of test results from one study population to another
population.
There are many other references in the literature to Spectrum
Bias,especially in Cardiological Diagnosis. I gave a short talk on it about
a year ago,and if anyone want the powerpoint slides/ references then drop
me an email.
Hope this helps,
Matt Williams
ITU SHO
Charing Cross Hospital
London
1. Lachs MS. Nachamkin I. Edelstein PH. Goldman J. Feinstein AR. Schwartz
JS. Spectrum bias in the evaluation of diagnostic tests: lessons from the
rapid dipstick test for urinary tract infection. [see comments.]. [Journal
Article] Annals of Internal Medicine. 117(2):135-40, 1992 Jul 15.
UI: 1605428
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