Rational Use of Diagnostic Tests
disease. Screening tests should be used to screen for diseases that (1) have serious
consequences if left undetected, (2) are reasonably prevalent within the population, and (3)
have treatment options readily available. Should a positive result be obtained, a more
accurate, confirmatory test should then be performed.
One example of a screening test would be the urine cortisol-to-creatinine ratio (Cort:Crt)u,
which is used to screen symptomatic patients for canine hyperadrenocorticism.[1,2] The
(Cort:Crt)u ratio tests for the presence or absence of urinary cortisol excretion and is
noninvasive and inexpensive. It also has a high diagnostic sensitivity, which means that a
negative result strongly indicates that the patient most likely does not have the disease.[1,2]
Urinary cortisol excretion can be caused by both pathologic and physiologic processes,
however, and the test cannot distinguish between the two. Therefore, the (Crt:Crt)u test is not
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