The "famous pairs" in Laboratory Medicine

Poor appropriateness of laboratory test prescription is a relevant problem in medicine and one of the reasons is that often physicians request "famous pairs" of biochemical tests. For instance, blood urea is typically ordered together with creatinine, plasma cholesterol is always coupled to triglycerides, erythrosedimentation rate is frequently associated to anti-streptolysin O titer and the same is true for transaminases, C-reactive protein and rheumatoid factor, anti-endomisial and anti-gliadin antibodies, amylase and lipase, prothrombin time and activated partial thromboplastin time, α-fetoprotein and carcinoembrionic antigen. This paper discusses the reason why most pairs are inappropriate and their request may generate results that are useless to clinical diagnosis. Laboratory should actively help physicians in requesting and interpreting laboratory tests. Assisting models can be useful (e.g., the laboratory could plan to perform a second level test only when the first level one is altered). More importantly, guidelines for a proper test prescription should be shared by laboratory and clinical scientific societies.