The complexities of predictive genetic testing

doi:10.1136/bmj.322.7293.1052

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This article has a correction

Please see: Predictive genetic tests can save lives but utility varies because most have uncertain predictive value

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James P Evans, director of cancer genetics servicesa (jpevans@med.unc.edu),
Cécile Skrzynia, genetic counsellora,
Wylie Burke, chairb

^a Department of Medicine, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
^b Department of Medical History and Ethics, University of Washington, Seattle, WA 98195, USA

Correspondence to: J P Evans

Predictive genetic testing is the use of a genetic test in an asymptomatic person to predict future risk of disease. These tests represent a new and growing class of medical tests, differing in fundamental ways from conventional medical diagnostic tests. The hope underlying such testing is that early identification of individuals at risk of a specific condition will lead to reduced morbidity and mortality through targeted screening, surveillance, and prevention. Yet the clinical utility of predictive genetic testing for different diseases varies considerably. We explore here the factors that contribute to this variation and which will dictate the utility of any of these new tests now or in the future.

Summary points

Predictive genetic testing has considerable potential for accurate risk assessment and appropriate targeting of screening and preventive strategies

Most predictive tests carry a degree of uncertainty about whether a condition will develop, when it will develop, and how severe it will be

The value of a predictive test depends on the nature of the disease for which testing is being carried out, how effective treatment is, and the cost and efficacy of screening and surveillance measures

Predictive testing must be tailored to individuals' preferences and the needs and experience of families

Methods and definition of terms

The observations in this paper derive from our experience in clinical medicine, medical genetics, genetic counselling, and molecular biology and from participation in educational programmes for generalists on medical genetics. The definition of utility used here encompasses all aspects of a test (individual and societal) that render it more or less useful in the clinical arena.

Difference from conventional medical testing

Current and future use

A conventional medical diagnostic test, such as a blood count or an imaging study, defines something about the patient's current condition. Although such information may have implications for the future, its overwhelming utility lies in the information it provides about the patient's current …