Table 2. Immunoassays used to evaluate fecal samples from an adrenocorticotrophic hormone challenge (ACTH).
Results indicated a high correlation for both validation methods used; parallel displacement curves and recovery of the standards. Cross-reactivities of each assay with associated glucocorticoid metabolites are indicated as well as the optimal dilution used for samples on each assay.
| Assay | Product Information | Parallelism | Recovery | Cross-reactivities | Dilution | |
|---|---|---|---|---|---|---|
| Correlation coefficient | Equation | Correlation coefficient | ||||
| Cortisol EIA (single antibody) | R4866 supplied by C.J. Munro, University of California, Davis, CA, USA | r = 0.98 | y = 0.88x + 89.17 | r = 0.98 | cortisol at 100%, prednisolone (9.9%), prednisone (6.3%), cortisone (5%), other metabolites at <1% | 1:200 |
| Cortisol RIA (double antibody) | Coat-A-Count, PITKCO-9, 2010-10-21, Siemens, Los Angeles, CA, USA | r = 0.98 | y = 1.40x +0.56 | r = 0.99 | prednisolone (76%), 11-deoxycortisol (11.4%), methylprednisone (11%), prednisone (2.3%), betamethasone (1.6%), other metabolites at <1% | 1:8 |
| Corticosterone EIA (double antibody) | R0006 supplied by C.J. Munro, UC Davis, Davis, CA, USA | r = 0.96 | y = 0.82x + 15.27 | r = 0.99 | corticosterone 100%, deoxycorticosterone 14.25%, progesterone 2.65%, other metabolites at <1% | 1:64 |
| Corticosterone RIA (double antibody) | I125 kit ImmuChem, MP Biomedicals, LLC Diagnostics Division Orangeburg, NY, USA | r = 0.95 | y = 1.31x + 51.92 | r = 0.99 | corticosterone 100%, other metabolites at <1% | 1:200 |