الفهرس 
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Abstract
The purpose of this work was to prepare in-house liquid phase radioimmunoassay system with high sensitivity, accuracy and stability for use in assessment of cortisol level in human serum. The work was achieved through: prepration of immunogen (Cortisol-21-hemisuccinate: Bovine serum albumin “C-21-hs: BSA”) with good molar ratio (17 cortisol molecule: 1 BSA molecule). The produced immunogen was immunized into two groups of New-Zealand rabbits with high dose for the first group and low dose for the second group, the best displacement percentage detected (76.5%) was for rabbit 1 (R1) from the first group after 4 weeks from the fourth booster injection at titer (1/8000). The tracer was prepared using chloramine-T oxidation method with a high radiochemical purity percentage (96%), radiochemical yield percentage (64.5%) and specific activity (150 µCi/µg). Also, a wide range of cortisol standards (0-60 µg/dl) was prepared using steroid assay buffer.
Establishment of cortisol liquid phase RIA system takes place using optimum conditions detected (37 oC, 3 hrs, 100 µl sample volume, 500 µl of 12 % PEG-8000, 1/200 dilution of NRS and 1/80 dilution of 2nd antibody).
Testing the validity show that the sensitivity was 0.1 µg/dl, coefficient of variations (CVs%) for intra-assay precision were (6.2, 5.8 and 7.9), while, for inter-assay precision was (8.1, 6.9 and 9.4) for the same low, normal and high pooled sera respectively. For accuracy, recovery of cortisol was ranged from (91.7% to 110.98%), (87.48% to 101.81%) and (87.08% to 95.82%) for three different concentrations of cortisol, while the results of parallelism, ranged from (86.7% to 96%), (94.6% to 100.5%) and (86.7% to 96.5%) for the same three concentrations used in recovery test respectively. The locally produced cortisol antibodies was tested and show to be highly specific for cortisol and with low cross-reactivity to other naturally occurring compounds. Method comparison study showed that the correlation coefficients were (r = 0.99914), when our locally prepared system compared with reference method commercially available (alpha diagnostic international, cortisol Elisa kit).
These results and observations show the success of the present study to prepare a sensitive, precise, accurate and stable assay to detect cortiol concentration in human serum.