Letters to the Editor GENETIC COUNSELING

To the Editor: We have read Dr. Edwards' critique of our book, Principles of Genetic Counseling [1], with the appropriate feelings: pleasure at the flattery and embarrassment at our mistakes. He has obviously read the text closely, and we can only regret that we did not have the benefit of such trenchant criticism before publication. Many of his points we would concede; with some we would sharply disagree; in some instances, he seems to have missed the point entirely. For instance, if he had applied the method of dummy consultands, he would not think it absurd to try to establish the probable genotype in a remote ancestor, even if the information were somewhat suspect. Again, we included an "unconventional" exposition of probability and quoted no standard reference precisely because attempts at explaining orthodox theory (which is designed by probabilists for probabilists in abstract situations) to people concerned with practical problems, like ourselves, has been so ineffectual. We shall not take your space in matching rhetoric for rhetoric, but there is one major misinterpretation of what we have said which is so grotesque that it cannot go unanswered. It occurs in the first paragraph and sets the whole tone of the critique. Either Dr. Edwards does not himself distinguish between reason and logic or he supposes that we do not. He seems to imply that we are proposing to substitute abstract argument (or possibly even "algebra") for empirical data. Nothing could be further from the truth. If, when he claims to be an empiricist, he means that empirical evidence is at once the foundation and the touchstone of science, we are as staunch empiricists as he. If (which we cannot believe) he means that he relies exclusively on such data at the expense of coherence, surmise, conjecture, verification, interpretation, and systematic application, then we have scarcely any common ground for discussion. If a disease is known (from observation) to follow an X-linked pattern of inheritance (the existence of which is known from observation), we use this model in arriving at a conclusion. Where many congenital defects are concerned, we have large gaps in our reasoning and must use model-free and distribution-free methods which, we were at pains to point out, are both less efficient and less secure. Where, as in giving a prognosis for mucolipidosis type IV, we do not even have fact (the disease being scarce, but newly recognized and only on a small scale), we are driven to common sense, tempered analogies with "similar" conditions, broad clinical experience, and the like. The "practical man" who does not understand the methods for handling to best advantage what data he has or deliberately turns his back on them may err grievously. A knowledge of physics alone may not make it possible to design bridges, but we would not trust ourselves in the hands of an engineer who dismissed what physics and the theory of design had to tell him. These examples illustrate what we mean by rating 301

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LETTERS TO THE EDITOR

reason first (which comprises all the appropriate sources of information with rationality and coherence added) and common sense alone last. EDMOND A. MURPHY GARY A. CHASE Division of Medical Genetics The Joseph Earle Moore Clinic The John Hopkins Hospital Baltimore, Maryland 21205 REFERENCE 1. EDWARDS JH: Review of Principles of Genetic Counseling, by MURPHY EA, CHASE GA. Am J Hum Genet 28:627-630, 1976

MASS NEONATAL SCREENING IN 1977

To the Editor: It has been 15 years since the development of an automated bacterial inhibition assay for hyperphenylalanemia ushered in the era of mass screening to presymptomatically identify persons with genetic disease [1]. Despite some early controversy over the risks of false positive diagnoses [2], during the mid-sixties more than 40 states passed laws requiring that newborns be tested for phenylketonuria (PKU). Since then a variety of technological developments have greatly increased the number of genetic disorders that can be detected in neonates [3]. During the past 5 years, a number of state public health departments have followed the lead of Massachusetts [3] and have expanded the scope of their phenylketonuria screening programs. In some states, special enabling laws have directed public health officials to this task, but most programs have been expanded after a policy decision made within the executive branch [4]. In February 1975, in an effort to ascertain the extent to which various state PKU programs had expanded, I surveyed the departments of public health. The results indicated that in at least nine states infants were being tested for one or more metabolic disorders other than phenylketonuria and that in at least five other states some infants were being tested for sickle cell anemia [5]. Responses to other questions in the survey indicated public health officials generally favored the expansion of screening efforts. In November 1976, I resurveyed the states to determine whether further expansion had taken place. Thirty-seven states replied to the initial mailing; a repeat mailing (6 weeks later) garnered seven more responses, giving me data on 44. Thus, the following compilation excludes seven states (Alabama, California, Kansas, New Hampshire, South Carolina, Tennessee, and Washington, D.C.) that did not respond. The results of my second (albeit crude) survey suggest that state support of mass neonatal screening has rapidly increased during the past 2 years. The number of states screening for galactosemia has risen from six to at least 17. At least nine states now screen for histidinemia, 11 for homocystinuria, 12 for maple syrup urine disease, and

Genetic counseling.

Letters to the Editor GENETIC COUNSELING To the Editor: We have read Dr. Edwards' critique of our book, Principles of Genetic Counseling [1], with th...
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