Counseling in medical genetics / Sheldon Reed.

  • Reed, Sheldon C. (Sheldon Clark), 1910-2003.
Date:
[1980], ©1980
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Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Counseling in medical genetics / Sheldon Reed. Source: Wellcome Collection.

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    94 / Cystic Fibrosis—A Challenge diagnosed at some time (1 in 1,600 frequency, 4,000,000 births annually). This is a disease of great significance, particularly when it is remembered that the cost of treating a single patient may be a financial disaster for the family. Clearly, this disease is one where screening of conjugal couples to determine whether both are carriers would be of great help. The most practical screening test is naturally that of finding the affected homozygous patient as soon after birth as possible. The wide spectrum of symp¬ toms which vary from patient to patient probably means that the basic defect is a number of metabolic steps prior to the observed pathology. Consequently, it will be more difficult to find a screening test useful for all patients. The tests should be capable of detecting in the newborn one or more aspects of chronic pulmonary disease, pancreatic exocrine deficiency, and abnormally high sodium and chloride concentrations in sweat. The disease escapes detection in some patients until young adulthood, and late diagnosis seems to become more, rather than less, common. The sweat electrolyte abnormality is present from birth and persists through¬ out life. The sweat test, when properly performed, is accepted as the simplest and most reliable laboratory procedure for confirming the diagnosis of CF in children. The method of choice seems to be that of Gibson-Cooke which is described in Appendix В of the NAS/NRC Committee Report [1976] on evaluation of testing for cystic fibrosis. The sweat test is not as definitive in persons over 18 as it is in children. Enzyme assay will be especially useful for adults as these patients may be tall, well nourished, and relatively healthy looking. Not only tryptic activity but activity of chymotrypsin and carboxypeptidase are absent or greatly reduced in CF. The most practical test for widespread screening of the newborn is the meconium test. All patients with meconium ileus and about 80% of all infants born with cystic fibrosis have abnormally high concentrations of albumin in their meconiums; see Stephan et al [1975]. According to Warren J. Warwick, MD, in a personal communication, with newborn infants having the genetics for cystic fibrosis, one would detect 80% of them but would miss the 20% who would be false negatives. No doubt many more than 20% are missed and die without diagnosis under present procedures. Consequently, newborn testing would be very useful for these cases. However, there would be about 1,200 false positives found for every 80 bona fide cases. These 1,200 babies would all have to be given the sweat test at about 4—6 weeks of age in order to eliminate the approximately 1,180 false positives and to find the remaining 20 real cases. In the meantime the 1,180 pairs of parents have been subjected to needless worry which is ethically undesirable. Except for the above complication there is no ethical objection to screening for the homozygous CF patient because treatment may be helpful when a patient is detected, that is, diagnosed. Early diagnosis is not only humane but a basic