To the Editor.—
The article by Crosby et al (227:310, 1974) concerning serum iron levels in normal people vividly illustrates that serious misconceptions regarding normal-range establishment persist. Even among laboratory-based physicians using a normal range established in other laboratories, on different patient populations, using different analytic techniques, and without regard for time of sample collection, the authors express amazement that 6% of blood donors in a small study and 3.5% of donors in a larger study had "high serum iron values."Establishment of normal range by use of the most common statistical tools (mean±2 SD) in the same laboratory, on the same population, and at the same time of day yields, under the most ideal conditions, 4.55% abnormals, approximately half above and half below the normal range.1 In addition, the authors do not point out that the normal range for their patient population is less than 1% prevalence of
Haven G. Normal Blood Iron Values. JAMA. 1974;228(5):568. doi:10.1001/jama.1974.03230300016014
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