Prognosis and prognostic research validating a prognostic model


19-Apr-2014 23:39

In the diagnostic setting, the probability that a particular disease is present can be used, for example, to inform the referral of patients for further testing, initiate treatment directly, or reassure patients that a serious cause for their symptoms is unlikely.

In the prognostic setting, predictions can be used for planning lifestyle or therapeutic decisions based on the risk for developing a particular outcome or state of health within a specific period (Steyerberg, 2009; Moons The nature of the prediction in diagnosis is estimating the probability that a specific outcome or disease is present (or absent) within an individual, at this point in time—that is, the moment of prediction (T=0).

These and other reviews provide a clear picture that, across different disease areas and different journals, there is a generally poor level of reporting of prediction model studies (Laupacis , 2014).

Furthermore, these reviews have shown that serious deficiencies in the statistical methods, use of small data sets, inappropriate handling of missing data, and lack of validation are common (Laupacis , 2014).

Doctors naturally integrate several patient characteristics and symptoms (predictors, test results) to make a prediction (see Box B for differences in common terminology between diagnostic and prognostic studies). Prediction models (also commonly called ‘prognostic models,' ‘risk scores,' or ‘prediction rules' (Steyerberg ).

Model development studies aim to derive a prediction model by selecting the relevant predictors and combining them statistically into a multivariable model.

Collins (2011) evaluated the methodological conduct and reporting of 39 reports published before May 2011 describing the development of models to predict prevalent or incident type 2 diabetes. The list was refined during several meetings of the steering group and in e-mail discussions with the wider group of TRIPOD contributors.The resulting TRIPOD Statement is a checklist of 22 items, deemed essential for transparent reporting of a prediction model study.To aid the editorial process and readers of prediction model studies, it is recommended that authors include a completed checklist in their submission (also available at

In medicine, patients with their care providers are confronted with making numerous decisions on the basis of an estimated risk or probability that a specific disease or condition is present (diagnostic setting) or a specific event will occur in the future (prognostic setting) (Box A).

This article describes how the TRIPOD Statement was developed.