Endocrine Abstracts (2001) 2 P94

CONVENIENT 'DELFIA' IMMUNOFLUORIMETRIC ASSAYS FOR PLASMA AND URINE 18-HYDROXYCORTISOL

KA Robb, B Joshi, G Barnard, P Quinlan, C Glenn, A Armston & PJ Wood


Regional Endocrine Unit, Southampton General Hospital, Southampton UK.


Plasma and urine 18-hydroxycortisol ('18-OHF') measurements are helpful to discriminate primary hyperaldosteronism (Conn's syndrome) caused by adrenal hyperplasia (normal 18-OHF) from adrenal adenoma or glucocorticoid suppressible hyperaldosteronism ( raised 18-OHF). We have developed DELFIA time-resolved fluorescence assays for 18-OHF as a second-line biochemical investigation for patients with raised plasma aldosterone/ renin ratios. Following ether extraction, test samples and standards were analysed in a system consisting of rabbit anti-18-OHF antiserum and biotinylated 18-OHF tracer using strip-format microtitre plates coated with goat anti-rabbit antiserum. Europium-labelled Neutralite avidin was used to detect bound tracer. The methods have been validated in terms of recovery, parallelism, specificity, detection limit and precision. Plasma 18-OHF reference ranges determined in 15 subjects were 0.7 to 6.5 nmol/L (supine) and 1.6 to 10.7 nmol/L (ambulant). The urine 18-OHF reference range, determined in 18 adults was 40-550 nmol/24 hours.

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