External Validation of clinical prediction models
Dr. Nancy Agnes, Head, Technical Operations, Statswork info@statswork.com
Validation, particularly external validation,
II. FACTORS INFLUENCES AFFECT
is a crucial part of developing a predictive
EXTERNAL VALIDATION DATA
model. External validation is needed to ensure
that
a
prediction
model
is
generalizable to patients other than those in
the
derivative
cohort.
External
The sample size for external validation data for the implementation of the prediction model is affected by the number of events and predictors.
validation can be done by testing the model's output in data that isn't the same as
External validation of the prediction model
the data used to create the model. As a
requires a minimum of 100 events and/or
consequence, it is carried out after the
non-events,
creation of a prediction model.
studies, and a systematic analysis found
according
to
simulation
that small external validation studies are I. EXTERNAL VALIDATION
ineffective
and
inaccurate.Example:
External validation can take many forms,
Radiology imaging is often treated as
including validation in the field such as
effective
temporal, geographical and independent
researchers often validate the findings
validation. For external validation studies,
using clinical prediction model. Every
the sample size calculation estimates
prediction
based on statistical power considerations
regression analysis. The most common
have not been extensively investigated.
predictive model or the regression model
However, in order to achieve adequate
used for the clinical prediction model are
model output in the validation set, a large
linear regression if the dependent variable
sample size is needed to validate the
is continuous in nature, logistic regression
prediction model.
model if the dependent variable is binary, and
predictive
model
is
Cox-proportional
parameters
based
model
on
if
and
the
the
dependent variable is time-to-event in
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