High diagnostic accuracy for idiopathic Addison's disease with a sensitive radiobinding assay for autoantibodies against recombinant human 21-hydroxylase.
Autoantibodies against 21-hydroxylase (P450c21) are common in idiopathic autoimmune Addison's disease. In the present work, we have developed a sensitive radiobinding assay using in vitro translated recombinant human 35S-P450c21. Levels of P450c21 antibodies (P450c21-Ab) were expressed as a relative index (P450c21 index) using a P450c21-Ab positive Addisonian serum and two antibody-negative healthy sera as positive and negative standards in healthy individuals. The upper level of normal was the mean + 3 SD. Positivity for P450c21-Ab was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of immunoprecipitated 35S-P450c21. In 38 Addisonian patients, P450c21-Ab were found in 24/28 (86%) idiopathic, 0/5 post-tuberculosis, 0/3 adrenoleukodystrophy, and 0/2 post-adrenalectomy sera. Among healthy individuals, 1/70 (1.4%) were positive. The P450c21 index, as an estimate of P450c21-Ab levels, correlated inversely with the duration of idiopathic Addison's disease (r = -0.527; P = 0.007): 16/16 (100%) positive in patients with less than 20 yr and 8/12 (67%) positive in patients with more than 20 yr disease duration. The availability of this simple and sensitive radiobinding assay to evaluate levels of P450c21-Ab will permit large clinical studies as well as screening subjects at risk. In addition, the general population can now be screened to evaluate the predictive value of P450c21-Ab for Addison's disease.
Falorni
A
A
Department of Molecular Medicine, Karolinska Institute, Stockholm, Sweden.
Nikoshkov
A
A
Laureti
S
S
Grenbäck
E
E
Hulting
A L
AL
Casucci
G
G
Santeusanio
F
F
Brunetti
P
P
Luthman
H
H
Lernmark
A
A
D000208:Acute Disease; D000224:Addison Disease / Q000175:diagnosis*; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000032:analysis*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D011869:Radioligand Assay / Q000379:methods*; D011994:Recombinant Proteins; D012016:Reference Values; D012680:Sensitivity and Specificity; D013255:Steroid 21-Hydroxylase / Q000276:immunology*
D001323:Autoantibodies; D011994:Recombinant Proteins; D013255:Steroid 21-Hydroxylase