Usefulness and limitations of an in-house direct radioimmunoassay for 17-hydroxyprogesterone in serum.

M. S. Lo, M. L. Ng, Loo Ling Wu, B. S. Azmy, B. A. Khalid

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Abstract

Since conventional radioimmunoassays (RIA) for measurement of 17-hydroxyprogesterone (17-OHP) in serum samples require a laborious solvent extraction step, a direct and rapid in-house RIA was developed for early diagnosis and management of congenital adrenal hyperplasia (CAH). In-house rabbit anti-17-OHP antiserum, tritium labelled 17-OHP and dextran-coated charcoal were used in assay buffer with low pH 5.1 and preheated serum samples. Both inter- and intra-assay CVs were < 10% and the sensitivity was 1.2 nmol/l or 12 fmol/tube. Results from the direct assay correlated well with values from an extraction assay, r = 0.88 in samples from CAH patients, r = 0.85 in adults and children, 0.69 and 0.40 in term and preterm neonates respectively, 0.66 and 0.63 in luteal phase and third trimester pregnancy; p < 0.001 in all groups except p < 0.05 in preterm neonates. However, results from the direct assay were two to three times higher in serum samples from CAH patients, normal adults and children, but were five to seven times higher in pregnancy and term neonates and thirty times higher in preterm neonates. The markedly elevated levels measured by the direct assay are probably due to cross-reactivities with water-soluble steroid metabolites such as 17-hydroxypregnenolone sulphate and dehydroepiandrosterone sulphate (DHEAS). Although the direct assay is only useful as a screening test for preterm babies, it can be used for both diagnosis and monitoring of treatment of CAH in all other age groups.

Original languageEnglish
Pages (from-to)43-52
Number of pages10
JournalThe Malaysian journal of pathology
Volume18
Issue number1
Publication statusPublished - Jun 1996

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17-alpha-Hydroxyprogesterone
Congenital Adrenal Hyperplasia
Radioimmunoassay
Newborn Infant
Serum
Dehydroepiandrosterone Sulfate
Tritium
Luteal Phase
Charcoal
Third Pregnancy Trimester
Dextrans
Immune Sera
Early Diagnosis
Buffers
Age Groups
Steroids
Rabbits
Pregnancy
Water

Cite this

Usefulness and limitations of an in-house direct radioimmunoassay for 17-hydroxyprogesterone in serum. / Lo, M. S.; Ng, M. L.; Wu, Loo Ling; Azmy, B. S.; Khalid, B. A.

In: The Malaysian journal of pathology, Vol. 18, No. 1, 06.1996, p. 43-52.

Research output: Contribution to journalArticle

Lo, M. S. ; Ng, M. L. ; Wu, Loo Ling ; Azmy, B. S. ; Khalid, B. A. / Usefulness and limitations of an in-house direct radioimmunoassay for 17-hydroxyprogesterone in serum. In: The Malaysian journal of pathology. 1996 ; Vol. 18, No. 1. pp. 43-52.
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