Am J Psychiatry 1984; 141:1550-1555
Copyright © 1984 by American Psychiatric Association
The dexamethasone suppression test in normal control subjects: comparison of two assays and effect of age
AH Rosenbaum, AF Schatzberg, RA MacLaughlin, K Snyder, NS Jiang, D Ilstrup, AJ Rothschild and B Kliman
he authors used competitive protein binding assay and radioimmunoassay to
measure cortisol levels in 38 normal control subjects three times before
and three times after administration of 1 mg of dexamethasone. They found
significant interassay differences at 11:00 p.m. before dexamethasone and
at all three postdexamethasone times. Analysis of variance revealed
significant overall positive relationships between age and cortisol levels
measured by both techniques. Age correlated significantly with
postdexamethasone cortisol levels measured by radioimmunoassay but not when
measured by competitive protein binding assay. Clinicians should obtain
data from their laboratories as to appropriate cutoffs for cortisol
suppression on the specific assay used.
