Efficacy of statewide neonatal screening for cystic fibrosis by assay of trypsinogen concentrations

Article Abstract:

Among white Americans, cystic fibrosis (CF) is the most common lethal genetic disorder. Some of the effects of the disease may be mitigated by early treatment, but there is not yet an early screening program for this disease. The definitive sweat test is too elaborate to be routinely performed on all infants, and its effectiveness for infants under three months of age is uncertain. A good preliminary screening protocol for infants would be rapid and cheap; the more elaborate sweat test could then be used to evaluate only those infants selected by the first pass of screening. A good candidate for a screening test is the level of trypsinogen in the blood. Under normal conditions, trypsinogen is converted into the digestive enzyme trypsin within the digestive tract. However, trypsinogen is manufactured in the pancreas, an organ which is seriously affected in CF; patients with cystic fibrosis have larger than normal amounts of trypsinogen in their blood. The test for trypsinogen is easy and may be performed on a drop of dried blood. To test the feasibility of using this test for the screening of infants, a testing protocol was designed and evaluated on 279,399 infants. In the testing protocol, all infants were tested for trypsinogen. Those with high amounts in their blood were tested a second time to rule out errors. The infants who were found to have increased amounts twice were then given the sweat test. If the sweat test was also positive, the infant was referred for further evaluation and treatment. A total of 73 cases of cystic fibrosis were identified; when adjusted for racial differences, the rate was 1 case per 2,251 white infants, close to the expected rate. During the course of the study, there were three known cases of CF missed by the screening test. Fewer than 8 percent of the infants testing positive on the first trypsinogen test actually had cystic fibrosis. This fraction is in keeping with first-pass accuracy for other genetic screening tests. The results of this study indicate that it is both possible and practical to establish a screening program for the early detection of cystic fibrosis among infants. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Medical screening, Health screening, Cystic fibrosis, Pancreas, Pancreatic secretions

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Screening for multiple endocrine neoplasia type 2a with DNA-polymorphism analysis

Article Abstract:

Multiple endocrine neoplasia type 2a (MEN2a) is an inherited disease which results in the development of thyroid cancer, tumors of the adrenal glands (which produce adrenal hormones), and overactivity of the parathyroid glands (which regulate the levels of calcium and phosphorus in the body). MEN2a has been linked with a particular genetic abnormality on chromosome 10, which allows for identification of carriers of this mutation by using various DNA probes, or markers. The genetic material of 130 members of 11 families of European and North African origin was analyzed, and all 11 families tested positive for at least one of three markers of the genetic abnormality. These results made it possible to provide genetic counseling for eight families. The findings demonstrated that this genetic screening, called restriction-fragment-length polymorphisms (RFLP) analysis, was more effective for detecting MEN2a carrier states than endocrine tests of the thyroid and parathyroid glands, especially in younger people. The greatest accuracy was obtained when genetic screening and endocrine testing were combined. It was recommended that, after diagnosis with genetic screening, individuals at risk for MEN2a be monitored for early signs of endocrine gland abnormalities, and counseled on the possible risks for their children. Early identification and surgical removal of thyroid cancer reduces the risk of metastasis (spread of the cancer). Relatives of MEN2a thyroid cancer patients should also be screened and observed for this genetic abnormality, and its manifestations. (Consumer Summary produced by Reliance Medical Information, Inc.)

Usage, DNA probes, Linkage (Genetics), Adenomatosis, Familial endocrine, Multiple endocrine neoplasia, Thyroid cancer, Parathyroid glands

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Ultrasonographic screening for fetal aneuploidy

Article Abstract:

Screening pregnant women with ultrasound to detect abnormalities in the fetal neck may identify chromosomal defects that require more invasive testing. In one study, this screening identified 54% of cases of Down's syndrome, a cause of mental retardation. Screening for nuchal translucency, indicative of fluid accumulating at the neck of the fetus, requires some technical precision, and studies have reported significant variation between ultrasound examiners. More experience in women at low risk for such fetal defects should precede widespread adoption of this screening test.

Ultrasound imaging, Fetus, Identification and classification, Chromosome abnormalities, Aneuploidy

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