Commercial Radioimmunoassays Do Not Measure Urinary Free Cortisol Accurately and Should Not Be Used for Physiological Studies
Bibliographic record
Abstract
In their recent article, Legro et al. (1) claim to have studied urinary free cortisol (UFC) in adolescent females using “established RIA methods that employ methanol extraction before assay.” They provide data for reproducibility (8%) and sensitivity (5 μg/24 h) and minimal data for cross-reactivity. No references are provided. It is not clear what the methanol extraction step consisted of or was meant to accomplish. The assays used are presumably commercial RIAs, none of which has been shown to measure UFC accurately. Such assays are validated only for serum or plasma cortisol and give values that are much too high for UFC, as shown more than 20 yr ago and many times since when compared with data obtained after HPLC or other extensive chromatography (2), or more recently by liquid chromatography-tandem mass spectrometry (3). The values obtained by RIA are usually about three or more times higher than the true values, due to competition by large amounts of metabolites or other forms of interference. Although such RIA methods may have some clinical use in determining excessive cortisol production, they are unsuitable for physiological studies if one wishes to measure cortisol itself.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.030 | 0.049 |
| Meta-epidemiology (narrow) | 0.002 | 0.002 |
| Meta-epidemiology (broad) | 0.005 | 0.001 |
| Bibliometrics | 0.003 | 0.004 |
| Science and technology studies | 0.001 | 0.004 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.004 | 0.001 |
| Research integrity | 0.004 | 0.003 |
| Insufficient payload (model declined to judge) | 0.009 | 0.013 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".