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Causality: well established
Causality assessment · Causality: well established
Clopidogrel and Thrombotic thrombocytopenic purpura: is the FAERS signal real?
A written Bradford Hill assessment of one drug–event pair. The grade is a judgement about the signal, not a statement that this drug causes this event in any one person; FAERS counts are reports, not rates.
Clopidogrel ↔ Thrombotic thrombocytopenic purpura
n=456 co-reports · PRR 15.7 · ROR 15.7
Clopidogrel carries a boxed warning for thrombotic thrombocytopenic purpura, a rare but life-threatening microangiopathy that can appear within days to weeks of starting; 456 co-reports give PRR 15.7. Prompt plasma exchange is required.
Regulatory basis: clopidogrel (Plavix) prescribing information — boxed warning for TTP.
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | Days to weeks after start |
| Strength | met | PRR 15.7 with 456 co-reports |
| Consistency | met | Reproduced across reports |
| Specificity | met | Fairly specific to thienopyridines |
| Biological gradient | not established | Not clearly dose-related |
| Plausibility | met | Immune-mediated mechanism |
| Coherence | met | Fits thienopyridine-associated TTP |
| Experiment | n/a | Too rare for trial detection |
| Analogy | met | Analogous to ticlopidine TTP |
This table is this page's own qualitative read of the literature cited above, not an automated or citation-gated assessment — see the note at the bottom of this page.
✗ No ClinicalTrials.gov results-posting trial in the top search hits for clopidogrel captured thrombotic thrombocytopenic purpura as a tracked adverse event in a usable structure. A rare, idiosyncratic haematological emergency is far below trial detection thresholds.