Rethinking our Thinking about Diagnostic tests: There is nothing Positive or Negative about a Test result

By ROBERT McNUTT, MD Making a diagnosis is easy if the test we use to make the diagnosis defines the disease. These sorts of tests, called “reference-standard” tests, when present at any level of the test’s result, make the diagnosis. A spinal fluid culture growing listeria or opioids in the urine are examples. Using reference-standard tests in clinical medicine, however, is not the norm. The reason for this is that reference-standard tests often don’t exist and if they do they may be dangerous, difficult to obtain, and costly. Hence, we use most often non-reference standard tests that can only raise or lower the likelihoods of diseases. There is nothing particularly new in these comments. Every reader will know such concepts as, the “sensitivity and specificity” of a test. Every reader will remember hearing about, or be able to construct, 2X2 tables showing the sensitivity of a test; the corresponding false negative percent; the specificity of the test; the corresponding false positive percent. But, despite the ever-present teaching of how tests ‘work”, it is my experience that physicians and patients have difficulty using the measures of a test’s value in clinical care. This difficulty is manifest in the observation that diagnosis mistakes may be common and the perceived mistake is the inciting event in up to 40% of malpractice cases. If the conceptual ideas for appropriate test characteristics are so clear and well taught, why is there...
Source: The Health Care Blog - Category: Consumer Health News Authors: Tags: THCB Robert McNutt Source Type: blogs