Justice et al described different levels of validation for a predictive system. The authors are from the Pittsburgh Veterans Affairs Health Care System, University of Pittsburgh, University of California San Francisco, San Francisco Veterans Affairs Medical Center, and the University of Pennsylvania.
Type of Validation
Involves
Level
internal
derivation and validation groups, one location
0
prospective
same location as internal validation, presumably random
1
independent
external, second location
2
multi-site
external, multiple locations
3
multiple independent
external, multiple locations, multiple groups
4
multiple independent with life-table analysis
extrenal, multiple locations, multiple groups, multiple time intervals
5
Transportability issues:
(1) historical (retrospective vs prospective)
(2) geographic (spectrum of locations)
(3) methodologic (spectrum of various methods)
(4) spectrum of disease severity
(5) follow-up period (spectrum of different time intervals)
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