In the article "Morning Plasma Cortisol Levels in Infants Treated with Topical Fluorinated Glucocorticosteroids" by Weston et al (Pediatrics 65:103, 1980) an error has been noted in the description of the method used for cortisol assay. Samples were assayed by the competitive-protein binding radioassay of Murphy, which permits measurement of cortisol in 0.1-ml aliquots of plasma (0.2 ml for a duplicate determination) with a coefficient of variation of 7%.1,2 The Spencer-Peet fluorometric method, noted incorrectly in the text, would require a much larger volume of plasma than that obtained from the infants. References: (1) Murphy BEP: Some studies of the protein-binding of steroids and their application to the routine micro and ultramicro measurement of various steroids in body fluids by competitive protein binding radioassay. J Clin Endocrinol Metab 27:973, 1967; (2) Morris HG, DeRoche G, Winkler SM, et al: Effect of oral prednisone on the measurement of plasma steroid concentrations by the competitive protein binding radioassay. J Pediatr 85:248, 1974.
- Copyright © 1980 by the American Academy of Pediatrics