The misclassification of depression and anxiety disorders in the multiple sclerosis prodrome: A probabilistic bias analysis
Bibliographic record
Abstract
BACKGROUND: Studies suggest that depression/anxiety form part of the multiple sclerosis (MS) prodrome. However, several biases have not been addressed. We re-examined this association after correcting for: (i) misclassification of individuals not seeking healthcare, (ii) differential surveillance of depression/anxiety in the health system, and (iii) misclassified person-time from using the date of the first MS-related diagnostic claim (i.e., a demyelinating event) as a proxy for MS onset. METHODS: In this cohort study, we applied a validated algorithm to health administrative ('claims') data in British Columbia, Canada (1991-2020) to identify MS cases, and matched to general population controls. The neurologist-recorded date of MS symptom onset was available for a subset of the MS cases. We identified depression/anxiety in the 5-years preceding the first demyelinating claim using a validated algorithm. We compared the prevalence of depression/anxiety using modified Poisson regression. To account for misclassification and differential surveillance, we applied probabilistic bias analyses; for misclassified person-time, we applied time-distribution matching to the MS symptom onset date. RESULTS: Our cohort included 9929 MS cases and 49,574 controls. The prevalence ratio for depression/anxiety was 1.74 (95 %CI: 1.66-1.81). Following correction for misclassification, differential surveillance using a detection ratio of 1.11, and misclassified person-time, the prevalence ratio increased to 3.25 (95 %CI: 1.98-40.54). When the same correction was conducted, but a detection ratio of 1.16 was applied, the prevalence ratio increased to 3.13 (95 %CI: 1.97-33.52). CONCLUSIONS: Previous conventional analyses were biased towards the null, leading to an under-estimation of the association between depression/anxiety and MS in the prodromal period. This first application of probabilistic quantitative bias analysis within MS research demonstrates both its feasibility and utility.
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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 | 0.131 | 0.204 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.009 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".