For years we have heard that "70% of clinical decisions rely on lab tests." While there is no question that lab tests are very often pivotal to a patient's management, a few years ago Mike Hallworth published a two page article that decimates the evidence base for this quotation.
Hallworth is a clinical biochemist in England; his 2011 paper is open access at Annals of Clinical Biochemistry, here.
Hallworth MJ (2011) The 70% claim: what is the evidence base? Ann Clin Biochem 48:487-8. (PMID 22045648)
See also discussion and citation by footnote in an International Federal of Clinical Chemistry deck by Khosrow Adeli and Simon Shorter, available online, here.