Incidence of neural tube defects in liveborn and stillborn infants in British Columbia over a 10-year period

Reports of an apparent decline in the incidence of neural tube defects (NTDs) have come from various parts of the world. If these findings are consistent they would have an important impact on prenatal diagnosis and on screening programs. The incidence of NTDs over a 10-year period was examined in British Columbia, a province that has a population-based health surveillance registry through which there is virtually complete ascertainment of liveborn infants with NTDs. The results showed a significant decrease in incidence only for stillborn infants with anencephaly. The increased use of ultrasonography and the subsequent termination of pregnancies in which the fetus has been found to have anencephaly may explain this observation.

A cost-benefit analysis of a population screening programme for neural tube defects

Population screening for neural tube defects is possible by measuring maternal serum alphafetoprotein levels with appropriate follow-up as required. British Columbia has approximately 39 000 births annually and the incidence of neural tube defects is 1.55 per 1000 births (0.94 per 1000 livebirths). Results from a cost-benefit analysis suggest that the outlined screening programme would be cost-beneficial for British Columbia. Other important factors essential to consider before instituting a population screening programme are discussed.

A cost-benefit analysis of prenatal diagnosis for neural tube defects selectively offered to relatives of index cases

Relatives of patients with neural tube defects (NTD) frequently request prenatal diagnosis for this problem, and it would be helpful to have information on cost-benefit aspects of offering this service to them. A cost-benefit analysis was done for selective prenatal diagnosis offered to parents and aunts of index cases as these are the two groups for which adequate empiric data are available. The results are extrapolated to other relatives. The study concludes that prenatal diagnosis is cost-beneficial if selectively offered for pregnancies where the fetus is a first or second degree relative of an index case. The results are discussed in terms of whether prenatal diagnosis should be offered to all aunts of index cases or only to maternal aunts. The lifetime costs of caring for an individual with spina bifida, in 1980 dollars, was calculated to be approximately $84,000.

The familial nature of multiple sclerosis: empiric recurrence risks for first, second-, and third-degree relatives of patients

Although the risks are low, relatives of multiple sclerosis (MS) patients have a greater risk of developing the disease than the general population. Since this is true of second- and third-degree relatives as well as first-degree relatives, the increased risk cannot be explained solely by environmental factors. This observation is part of the evidence that the etiology of MS may have a genetic component. Genetic counseling is recommended for MS patients. Empiric recurrence risks have been derived and give the counselor necessary information with which to provide this service.

A cost-benefit analysis of prenatal detection of Down syndrome and neural tube defects in older mothers

Infants of older mothers have an increased risk of Down syndrome. As public awareness of this disorder increases, so does the number of women requesting prenatal diagnosis for advanced maternal age. A cost-benefit analysis was done to determine the maternal age for which screening for Down syndrome is cost-beneficial. The analysis took into account the cases of neural tube defects which would be detected "incidentally" on amniocentesis, as all amniotic fluid samples have alpha fetoprotein levels measured. British Columbia (B.C.) provides a unique opportunity for such a study: single-year maternal age risk figures for Down syndrome based on virtually complete ascertainment are available; the Department of Medical Genetics Prenatal Diagnosis Clinic is the main referral centre for the province; B.C. has a universal medicare system which facilitates the calculation of medical costs and gives all women financially equal access to prenatal diagnosis. The study concludes that prenatal screening for Down syndrome is cost beneficial for women 34 years old or older at conception. A discount rate of 14% was chosen for this analysis and the effect of such a rate on the results is discussed.

A goodness-of-fit test for the polygenic threshold model: application to multiple sclerosis

Recently it has been suggested that multiple sclerosis may be a multifactorial disorder. We found in British Columbia 364 families (sibship size greater than or equal to 2) in which at least on sibling was diagnosed as having "clinically definite" multiple sclerosis. The data were tested for goodness-of-fit to the multifactorial model using an analysis that considers various parameters including ascertainment probability heritability, and sex-dependent prevalence rates. The results suggest that multiple sclerosis does not fit the multifactorial model. As an alternative genetic model we propose that a major gene could be responsible for at least a portion of the cases of multiple sclerosis.