Deconvoluting synovial fluid molecular endotypes in knee osteoarthritis: primary results from the STEpUP OA Consortium
Bibliographic record
Abstract
ABSTRACT Background Osteoarthritis (OA) has a lifetime risk of over 40%, imposing a huge societal burden. Clinical variability suggests that it could be more than one disease. S ynovial fluid T o detect E ndoty p es by U nbiased P roteomics in OA (STEpUP OA) was established to test the hypothesis that there are detectable distinct molecular endotypes in knee OA. Methods OA knee synovial fluid (SF) samples (N=1361) were from pre-existing OA cohorts with cross-sectional clinical (radiographic and pain) data. Samples were divided into Discovery (N = 708) and Replication (N=653) datasets. Proteomic analysis was performed using SomaScan V4.1 assay (6596 proteins). Unsupervised clustering was performed using k-means, assessed using the f(k) metric, with and without adjustments for potential confounders. Regression analyses were used to assess protein associations with radiographic (Kellgren and Lawrence) and knee pain (WOMAC pain), with and without stratification by body mass index (BMI) or biological sex. Adjustments were made for cohort (random intercept) or intracellular protein, using an intracellular protein score (IPS). Analyses were carried out in R according to a pre-published plan. Results No distinct SF molecular endotypes were identified in OA but two indistinct clusters were defined in non-IPS regressed data which were stable across subgroup analyses. Clustering was lost after IPS regression adjustment. Strong, replicable protein associations were observed with radiographic disease severity, which were retained after adjustment for cohort or IPS. Pathway analysis identified a strong “epithelial to mesenchymal transition (EMT)” pathway, and weaker associations with “angiogenesis”, “complement” and “coagulation”. The latter were variably lost after adjustment for BMI or biological sex. Associations with patient reported pain were weaker. Conclusion These data support knee OA as a biologically continuous disease in which disease severity is associated with a strong, robust, tissue remodelling signature. Subtle differences were found in pathways after stratification by BMI or sex.
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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 | 0.010 | 0.019 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.001 | 0.004 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".