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Natural History Study of Prognosis

  1. Avital Cnaan

Published Online: 15 JUL 2005

DOI: 10.1002/0470011815.b2a04028

Encyclopedia of Biostatistics

Encyclopedia of Biostatistics

How to Cite

Cnaan, A. 2005. Natural History Study of Prognosis. Encyclopedia of Biostatistics. 5.

Author Information

  1. University of Pennsylvania, Philadelphia, PA, USA

Publication History

  1. Published Online: 15 JUL 2005


Prognosis refers to the probable outcome of an attack of disease. The traditional definition would describe the evolution of disease in the absence of medical intervention, but nowadays we may also include the term “clinical course” to describe the natural history of a disease that has been affected by medical intervention. Various design considerations are reviewed for the study of natural history, including the use of cohort studies, the various biases that may affect such studies, and the definition of time zero as a clearly defined starting point. Other topics include the analysis of dichotomous outcomes, survival analysis and longitudinal data analysis. Combination of data from several studies, and situations involving multiple outcomes are also mentioned.


  • study design;
  • bias;
  • data analysis;
  • data synthesis;
  • multiple outcomes