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ETHICAL AND LEGAL ASPECTS OF PREDICTIVETESTING

SIR,-For disorders where preventive measures are available,early testing for risk of disease could be beneficial. Thus, if a simpletest such as measurement of serum cholesterol uncovers

predisposition to coronary heart disease, individuals at high riskcould modify the risk by changing their life-styles. Even whenpreventive measures are not available, predictive tests may helppeople to make important decisions, such as whether or not to havechildren. Someone at risk for an autosomal dominant disorder inmid-life, such as Huntington’s disease, would be able to make moreresponsible choices if he knew for certain that he carried the gene orcould obtain definite reassurance that he did not.

However, predictive testing can be to an individual’s dis-

advantage. Insurance companies, pension funds, employers, andeducational and other institutions could request information on a

person’s risk status and this could result in refusal of application for,say, life insurance. One of us (K. B.) has repeatedly arguedl-3 thatlegislation is necessary to avoid the results of predictive tests beingused to the individual’s disadvantage since such uses would

discourage the beneficial application of such tests. It could have

discriminatory and other negative effects if insurance companiesand others continue to have a right even to ask questions aboutpredictive tests.I-3Developments in DNA technology make it likely that predictive

tests will soon be available for a broad spectrum of diseases. A DNA

polymorphism genetically linked to Huntington’s disease is alreadybeing used for predictive purposes, and there are claims for anassociation between DNA variants and predisposition to coronaryheart disease. Obesity has been reported to be strongly influencedby genetic factors, and if this is confirmed the relevant genes may beidentified. Regardless of the fate of associations claimed so farbetween diseases and genetic markers, it is difficult to avoid theconclusion that there will soon be impressive developments withrespect to possibilities for predictive testing.4These developments make it necessary to initiate discussion,

hopefully ending in legislation, to secure the advantageous use ofpredictive tests and to protect the individual against untoward usesof test results. Legislation is a slow process and there is no time tolose. The results of predictive tests should be the exclusive propertyof the individual and nobody else has the right to pass on suchinformation. Furthermore, insurance companies and others shouldbe forbidden to ask for a test to be done or to ask about tests that mayor may not have been done previously. In most countries suchprotection of the individual would require new laws.The proposed action would also help to avoid situations where

responsible people, taking tests to try to protect their own health,are selectively penalised. Furthermore, if it were to be forbidden toask questions about predictive tests, there would be less lyingconnected with entry into insurance or pension schemes or jobapplications. Life insurance premiums already take into account allrisks for death, disease, or incapacity. The ethical justification forinsurance companies and commercial pension schemes seems to bethat a great number of people absorb the expenses of those lessfortunate, knowing that they themselves and their families would beprotected in case of disease or death. The use of predictive tests toincrease revenues lacks such ethical justification.

Fogarty International Center,National Institutes of Health,Bethesda, Maryland, USA

Clinical Center, NIH

KÅRE BERG*

JOHN FLETCHER

*Present address: Institute of Medical Genetics, University of Oslo, Oslo 3, Norway.

1 Berg K. Ethical problems arising from research progress in medical genetics. In: BergK, Tranoy KE, eds. Research ethics New York- Alan R. Liss, 1983: 261-75

2 Berg K Problems in monitoring population groups at high risk Hereditas 1984, 100:175-77

3 Berg K Etiske problemer i forbindelse med genetisk veiledning. In: Vejlsgaard R, ed.Medicinsk årbog. Copenhagen Munksgaard, 1985: 19-28

4 Merz B. Geneticists ponder ethical implications of screening JAMA 1985; 254: 3160.

QUETELET INDEX AS INDICATOR OF OBESITY

SIR,-Your March 8 editorial states that "Obesity is convenientlydefined by use of the Quetelet, or body mass index, W/H2". I agreethat this index is convenient, primarily because of its simplicity, andthat it is general accepted as the best of the many height-weightindices available, but it is not a very accurate index of fat content orobesity.

In a survey of 5072 males aged 16-56 years2 data collectedincluded height, weight, and fatness skinfold measurements. 3In allage groups W/H was more closely related to weight (averager=0-86, residual SE=24) than it was for fat content (averager=0-78, residual SE = 36).

Any index utilising only height and weight takes no account ofbody build. The figure shows a histogram of fat free mass (FFM) (ie,body weight minus fat mass) for 150 males weighing between 70 and71 - 9 kg and with heights between 175 and 179 - 9 cm.’While theindex had a narrow range (21 - 6 to 23 - 5) FFM had a range of about10 kg and fat content ranged from 10 to 24% fat.

Distribution of FFM (kg) in 150 males weighing 70-71-9 kg and175-179-9 9 cm in height.

The same problem exists when defining a W/Hz index for obesity,such as 27. In the population studied fat contents in individualswith W/H values over 27 ranged from about 17% to 30%. Whilesomeone with a fat content of 30% is obese, 17% is about average forhealthy, relatively active 20-25-year-olds and certainly does notindicate obesity.

The average (±SD) Quetelet index and fat content in the17-19-year-olds and 50-56-year-olds studied2 were 22±2-3 and15:i::4’ 1 % and 26:i::3’ 0 and 27:i::5’ 3%, respectively. The men aged50-56 were therefore approaching the proposed obesity level of 27,but subjectively these men were on average nowhere near obese.One factor involved in their high fat content is the increase in theproportion of internal fat with age. A Quetelet index of27 in a youngman is more likely to indicate obesity than the same value in a50-year-old. Age should therefore be taken into account wheninterpreting W/Hz values.

In summary, W/H is of little value when assessing obesity inindividuals. If it is used as a convenient indicator in populationstudies, its limitations should be taken into account. Where possiblealternative methods for measuring fat content should be used.

Syntex Research Centre,Research Park,Heriot-Watt University,Riccarton, Edinburgh EH 144AS FRANCES C. MACDONALD

1. Roche AF, Siervogel RM, Chumlea WC, Webb P. Grading body fatness from limitedanthropometric data. Am J Clin Nutr 1981, 34: 2831-38.

2. McKay FC A new method for assessing fatness from an anthropometric study on 8799British adults. PhD thesis, Glasgow University, 1983

3. Durnin JVGA, Womersley J Body fat assessed from total body density and its

estimation from skinfold thickness: Measurements on 471 men and women aged 16to 72 years Br J Nutr 1974; 32: 77-97.