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Collecting Saliva and Measuring Salivary Cortisol and Alpha-amylase in Frail Community Residing Older Adults via Family Caregivers
Published on: December 18, 2013
[Measurement of salivary cortisol with four commercial kits]
K Nahoul1, M C Patricot, N Bressot
1Fondation de recherche en hormonologie, Fresnes, France.
Insights
Evaluating four commercial immunoassays for salivary cortisol measurement revealed none were fully adequate. However, incorporating a chromatographic step significantly enhanced specificity, with the Coat-A-Count kit showing the most promising results.
Area of Science:
- Endocrinology
- Biochemistry
- Analytical Chemistry
Background:
- Accurate salivary cortisol measurement is crucial for assessing adrenal function.
- Commercially available immunoassays vary in their suitability for direct salivary analysis.
Purpose of the Study:
- To evaluate the performance of four commercial immunoassays for salivary cortisol determination.
- To assess the impact of sample extraction and chromatographic purification on assay accuracy and specificity.
Main Methods:
- Four immunoassays (enzyme-immunoassay, two fluoro-immunoassays, radioimmunoassay) were tested.
- Sample preparation involved direct analysis or extraction (methylene chloride, Bond Elut).
- Assay results were compared against a reference method involving Sephadex LH 20 chromatography.
Main Results:
- No tested immunoassay was deemed fully adequate for salivary cortisol measurement under the study conditions.
- The introduction of a chromatographic step significantly improved assay specificity.
- The Coat-A-Count radioimmunoassay kit, particularly with chromatography, yielded the most comparable results to the reference method, though discrepancies occurred at low cortisol levels.
Conclusions:
- Current commercial immunoassays may require modification, such as chromatographic purification, for reliable salivary cortisol quantification.
- The Coat-A-Count kit demonstrates potential for salivary cortisol measurement when combined with appropriate sample processing techniques.
- Further optimization is needed to address discrepancies at low concentration levels for improved clinical utility.
Abstract:
Salivary cortisol was determined with four commercially available immunoassays: one enzyme-immunoassay (Cortisol Biotrol), two fluoro-immunoassays (TDX, Abbott; Stratus, Baxter) and one radioimmunoassay (Coat-A-Count, Behring). In order to improve the sensitivity of these immunoassays, it was necessary to increase sample volumes. Thus an extraction step had to be included in the procedure. It was performed with either methylene chloride or Bond Elut. However, the Coat-A-Count kit may be applied directly on salivary aliquots. The results obtained were compared to those yielded by the reference technique which includes a chromatographic step on Sephadex LH 20. According to the present data (n = 20) no kit appears to be adequate for salivary cortisol measurement at any level, at least in the conditions applied in this study. However, the introduction of a chromatographic step in the procedure improved greatly the specificity. Nevertheless, the best results were obtained with the Coat-A-Count kit. Indeed, they were generally similar to those of the reference technique, but some discrepancies were observed at low levels.
