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Highly sensitive microassay for aldosterone in unextracted plasma: comparison with two other methods
The Journal of Laboratory and Clinical Medicine
|November 1, 1984
Summary
A new direct radioimmunoassay offers a simple, sensitive method for measuring plasma aldosterone. This accurate technique provides results identical to established methods, simplifying clinical diagnostics.
Area of Science:
- Endocrinology
- Clinical Chemistry
- Assay Development
Background:
- Accurate measurement of plasma aldosterone is crucial for diagnosing and managing conditions like hyperaldosteronism.
- Traditional methods often involve complex extraction and chromatography steps, increasing time and cost.
- A need exists for a simpler, more direct assay for routine clinical use.
Purpose of the Study:
- To develop and validate a direct radioimmunoassay for plasma aldosterone.
- To compare the performance of the new direct assay with existing methods.
- To establish normal reference ranges for plasma aldosterone using the new assay.
Main Methods:
- Development of a direct radioimmunoassay using 125I-labeled aldosterone and a specific antiserum.
- Comparison with a standard assay involving methylene chloride extraction and column chromatography.
- Comparison with a micromethod using methylene chloride extraction only.
- Assay validation including sensitivity, precision (within- and between-assay variation), and correlation studies.
Main Results:
- The direct radioimmunoassay can measure aldosterone concentrations as low as 2 pg/ml in 25 microliters of plasma.
- Excellent precision was demonstrated with within-assay coefficients of variation ranging from 4.0% to 5.3% and between-assay variation from 5.0% to 9.4%.
- High correlation coefficients (0.97-0.99) were observed among the three methods, with results virtually identical to the standard chromatography method.
- Normal plasma aldosterone values in seated humans on unrestricted salt intake were determined to be 68 +/- 28 pg/ml.
Conclusions:
- A simple, direct microradioimmunoassay for plasma aldosterone has been successfully developed.
- The assay is accurate across a wide range of concentrations, highly sensitive, and provides results comparable to established methods.
- This direct assay offers a significant advancement for routine clinical laboratory analysis of plasma aldosterone.