Including a brief clinical history on laboratory submissions is critical for a multitude of reasons. One of the most important being that it enables diagnosticians to assemble a complete differential diagnosis list and thus facilitates appropriate test selection up front to ensure rapid turnaround of results. Safety and rapid diagnosis of zoonotic agents is another reason: For instance, tissues submitted from a cat with acute illness, high fever and history of contact with rabbits would alert the pathologist to request Francisella tularensis (tularemia) PCR testing. A test which would not be routinely ordered in the absence of case history or lesions (if tissues were included for histopathology). If a select agent is suspected (Brucella spp., Bacillus anthracis, F. tularensis, Y. pestis) it is important to contact the laboratory to ensure the sample is handled properly. See our Anthrax, Plague, and Tularemia Submission Guidelines document for more information.
Along with appropriate test selection clinical history is also necessary for interpretation of some results. It is particularly important for bacteriology where the clinical history is used to ensure the specimen is set up on the appropriate type of media(s) and culture condition(s). Many bacteria require special media for growth and unless adequate clinical history is submitted a specimen may not be cultured for specific bacteria. For more examples of how clinical history informs culture setup and interpretation, check out this article from the American Society for Microbiology (ASM). Thorough clinical case histories help the lab help you make the right diagnosis.