{"entity":{"id":"external-validation","kind":"term","name":"External validation","aka":["external validation","externally validated","external cohort","independent cohort","independent validation","external test set","generalisability","generalizability"],"tldr":"External validation tests a model on patients from a different hospital, country or platform than it was trained on; it is the only evidence that a result travels.","summary":"External validity is the extent to which a study's conclusions generalise to other situations, people and times (Wikipedia). For a prognostic model that means an independent cohort, ideally collected by other people on another platform: TCGA-trained survival models are routinely tested on METABRIC, and the concordance index typically falls, sometimes to chance. A model with no external validation has an internal estimate, not a result, and several OnCo ideas argue that multi-site validation should precede clinical use.","asOf":"2026-09-24","wikipedia":"https://en.wikipedia.org/wiki/External_validity","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/External_validity"}],"tags":["cansim-terms"],"related":["idea-tr2-ai-external-validation-registry","idea-data-multisite-validation-precondition","cancer-ai-vocabulary"],"cancers":[],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["train-test-discipline","domain-adaptation","calibration","analytical-vs-clinical-validation"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":["Listed in the CanSim terms map 1.0.0 (docs/onco/terms.json, generated 2026-09-24), CC BY 4.0, attribution: CanSim project, an open, public-data-first cancer foundation-model programme; CanSim page path /terms/external-validation."],"provenance":{"editedBy":"OnCo CanSim terms wave (Wikipedia summaries, standards and project pages, GDC and FDA pages, Europe PMC)","editedOn":"2026-09-24","note":"CanSim terms map 1.0.0 (docs/onco/terms.json, generated 2026-09-24), CC BY 4.0, attribution: CanSim project, an open, public-data-first cancer foundation-model programme"},"category":"Methods and models"},"route":"/terms/external-validation/","neighbours":{"idea":[{"id":"idea-tr2-ai-external-validation-registry","kind":"idea","name":"A registry of external validation datasets for cancer AI models, with mandatory reporting","route":"/ideas/idea-tr2-ai-external-validation-registry/"},{"id":"idea-data-multisite-validation-precondition","kind":"idea","name":"External validation at five or more sites in two countries before clearance","route":"/ideas/idea-data-multisite-validation-precondition/"}],"term":[{"id":"analytical-vs-clinical-validation","kind":"term","name":"Analytical versus clinical validation","route":"/terms/analytical-vs-clinical-validation/"},{"id":"calibration","kind":"term","name":"Calibration: reliability diagrams and the Brier score","route":"/terms/calibration/"},{"id":"cancer-ai-vocabulary","kind":"term","name":"Cancer AI vocabulary (CanSim terms map)","route":"/terms/cancer-ai-vocabulary/"},{"id":"clinical-covariates","kind":"term","name":"Clinical covariates (age, stage, nodes, treatment flags)","route":"/terms/clinical-covariates/"},{"id":"cross-validation","kind":"term","name":"Cross-validation and stratified k-fold","route":"/terms/cross-validation/"},{"id":"domain-adaptation","kind":"term","name":"Domain shift and domain adaptation (cell line to patient)","route":"/terms/domain-adaptation/"},{"id":"drug-response-splits","kind":"term","name":"Drug-response data splits: leave-cell-line-out, leave-drug-out, leave-tissue-out","route":"/terms/drug-response-splits/"},{"id":"microarray-expression","kind":"term","name":"Microarray expression data","route":"/terms/microarray-expression/"},{"id":"train-test-discipline","kind":"term","name":"Train, validation and test split discipline","route":"/terms/train-test-discipline/"}]}}