What is a Prognosis?

Prognosis is a term used in science and medicine which refers to determining the predicted or probable level of improvement in function, and the amount of time needed to reach that level of improvement in a health condition. It may also include a prediction of levels of improvement reached at several intervals during a course of therapy.

In the context of medicine, it describes a prediction of a patient's future condition. It is expressed using general terms such as poor, favorable, moderate, excellent, excellent, fair, or hopeless. The conditions that a prognosis is applied to include both diseases or conditions, as well as the outcome expected from an intervention. This intervention can be preventative (described as prophylactic) or operative.


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The implications of prognosis

Prognostic studies aimed to understand the course, determinants, or probability of outcomes in a cohort of patients. Prognostic information is useful for the following reasons:

  • To provide information to patients
  • To identify target groups for treatment
  • To target specific prognostic factors for modification throughout treatment
  • To provide the basis of personalized or risk-based medicine
  • The design of randomized trials

Several primary studies examine prognostic factors, biomarkers, tests, and models, and a systematic review of this evidence has been conducted. The Prognosis Methods Group has made progress in developing and testing new tools and methods for designing, conducting, and quantitively synthesizing, interpreting, and reporting systematic reviews of prognosis studies. The project is still ongoing.

The need to develop systematic reviews of prognosis studies is essential in helping facilitate the interpretation and usability of prognosis study findings and to identify gaps in the literature. This work has been conducted since 2016, being formally implemented within Cochrane.

With these recent methodological developments in tools come up it is becoming increasingly possible to review prognosis studies that are hoped to have an impact on clinical practice.

What is a prognostic factor?

A prognostic factor is any variable that is associated with a risk of a health outcome among people with a particular health concern. Defined in a more detailed way a prognostic factor is a measurement that has a relationship with a clinical outcome in the absence of therapy or when standard therapy is applied.

Different categories or values of any particular prognostic factor or associated with either better or worse outcomes for future health.

For example, in the instance of cancer, tumor grade at the time of histological examination is considered to be a prognostic factor because it is frequently associated with the time to death or disease recurrence. Prognostic scores often provide a more objective or more accurate prognosis than clinical predictions alone.

Routinely collected patient characteristics are considered to be prognostic. These include sex, age, body mass index, blood pressure, smoking status, the presence of other diseases (comorbidities), or symptoms.

Prognostic factors also include biomarkers, biomarkers are molecular variables that include a diverse range of imaging, electrophysiological, blood, urine, and physiological measurements.

Prognostic vs predictive outcomes

Prognostic factors are distinct from predictive factors, however. A predictive factor is a measurement that is associated with response or an absence of response to a particular therapy. Commonly, responses are defined using clinical endpoints commonly used in clinical trials. A predictive factor implies that there is a measurable benefit from the therapy that can be seen using a predictive biomarker.

In short, a prognostic biomarker provides information about the patient's overall cancer outcome, regardless of therapy, whilst a predictive biomarker gives information about the effect of a therapeutic intervention.

Accuracy of prognosis

The accuracy of chemical prognosis is difficult to predict. A systematic review of predictions of survival in palliative care patients analyzed 4642 records to determine the accuracy of clinicians' estimates of survival until determine if any clinical profession shows greater prognostic accuracy.

This revealed that prognostic accuracy is highly heterogeneous in palliative care, with the evidence suggesting that clinicians' predictions are more likely to be inaccurate. Moreover, no subgroup of connexion was shown to be more accurate at prognosis.


  • White N, Reid F, Harris A, et al. (2016) A Systematic Review of Predictions of Survival in Palliative Care: How Accurate Are Clinicians and Who Are the Experts? PLoS One. doi:10.1371/journal.pone.0161407.
  • Riley RD, Moons KGM, Snell KIE, et al. (2019) A guide to systematic review and meta-analysis of prognostic factor studies. BMJ. doi:10.1136/bmj.k4597.
  • Clark GM. (2008) Prognostic factors versus predictive factors: Examples from a clinical trial of erlotinib. Mol Oncol. doi:10.1016/j.molonc.2007.12.001.

Further Reading

Last Updated: Oct 22, 2021

Hidaya Aliouche

Written by

Hidaya Aliouche

Hidaya is a science communications enthusiast who has recently graduated and is embarking on a career in the science and medical copywriting. She has a B.Sc. in Biochemistry from The University of Manchester. She is passionate about writing and is particularly interested in microbiology, immunology, and biochemistry.


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