Normal Ranges and "Errors"

Excerpt

To the Editor: Dr. Burnum's recent valuable perspective (1) on "The Misinformation Era" spreads well-meant misinformation under the heading "Laboratory and Personnel Errors" by using the words "false" and "error" to describe the 5% of laboratory results that fall outside the normal range.

The normal range has no direct relation to disease. Normal range is traditionally defined as the central 95% of values in a population. The outer 5% are outside not by error or by illness but by definition. They obviously include the healthy as well as the sick. For certain purposes we should improve a test's properties by