Evidence for an informal clinical policy resulting in high use of a very-low-yield test

The actual and self-reported practice regarding the use of cerebrospinal fluid cultures for Mycobacterium tuberculosis was examined. All neurology house staff members surveyed, 62 percent of internal medicine house staff members, and none of pediatric house staff members reported that they would order mycobacterial cultures of cerebrospinal fluid routinely. The actual practice was comparable, with 71 percent of cerebrospinal fluid specimens being subjected to culture for mycobacteria on the neurology service, 65 percent on the internal medicine service, and 6 percent on the pediatric service. In this practice, medicine and neurology house staff differ significantly from their pediatric colleagues (p less than 0.001) and from the stated practice of their respective faculties (p less than 0.01). For at least six years, most medicine and neurology house staff have commonly applied an informal clinical policy of routinely culturing cerebrospinal fluid specimens for mycobacteria, despite a low suspicion of disease, lack of faculty support for the practice, and a zero yield for the test. Informal clinical policies such as this may be an important contributor to the problem of technology overuse.