It has been suggested that evidence-based laboratory medicine (EBLM) could help to improve the pertinence and accuracy of medical guidelines. In order to demonstrate this, we have used an EBLM approach (i.e. a systematic review) to examine three recently published guidelines that gave quite conflicting recommendations regarding the use of laboratory variables in the management of primary non-small cell lung cancer patients. In recommending the routine measurement of serum albumin, and, to a lesser extent, that of serum calcium in the pre-therapeutic prognostic evaluation of the advanced disease, the American Thoracic Society and the European Respiratory Society were probably correct with regard to calcium but perhaps mistaken regarding albumin. Some of the recommendations of the European Group on Tumour Markers regarding the usefulness of routine measurements of tumour markers (carcinoembryonic antigen (CEA), cancer antigen 125 (CA 125), tissue-polypeptide antigen (TPA)) in the pre- and/or post-therapeutic prognostic evaluation can also be criticised. In addition, the latter society as well as the Société de Pneumologie de Langue Française did not even try to list laboratory variables, others than tumour markers, that would be useful to stratify patients participating in clinical trials (i.e. lactate dehydrogenase (LDH), albumin, calcium, blood cell count, etc.), and the laboratory variables listed by the two former societies were probably not the right ones in this context: in particular LDH and tumour markers (fragments of cytokeratin 19 (Cyfra 21-1), tissue-polypeptide-specific antigen (TPS), neuron-specific enolase (NSE)) were not mentioned. Most, if not all of these discrepancies in the current medical practice guidelines might have been avoided had an EBLM approach been used by the authors.