Incremental cost-effectiveness of incorporating oestriol evaluation in down syndrome screening programmes

As screening for Down syndrome becomes increasingly sophisticated, it is important to evaluate the newer technologies in terms of their cost-effectiveness. One recent addition to Down syndrome screening programmes is maternal serum unconjugated oestriol (uE₃), especially when used in conjunction with maternal serum α-fetoprotein and human chorionic gonadotropin. Using assumptions used in a California proposal to justify an expanded screening programme for Down syndrome, we calculated both the average and the incremental cost-effectiveness of adding uE₃. Using the base case assumptions, including an $8 fee for the uE₃, the incremental cost-effectiveness of adding uE₃ to the proposed California programme is $119 100 per case detected, a value that compares favourably with other Down syndrome screening programmes. The sensitivity analysis supports this conclusion over a wide range of assumptions. However, because of the uncertainty with some key data, it is still too early to fully support the inclusion of uE₃ in Down syndrome screening programmes.     

Prenatal diagnosis and outcomes of five cases of mosaicism for an isochromosome of 20q

Five cases of mosaicism for an isochromosome of 20q have been detected from a total of 50 000 cases analysed for prenatal diagnosis by amniocentesis. Karyotypes were designated mos 46,X_/46,X_,i(20q). In all cases, the abnormal cell line was detected in more than one primary culture, thus fulfilling the criterion for true (level III) mosaicism. Indications for prenatal diagnosis were parental anxiety (two cases), low maternal serum alpha-fetoprotein (AFP) (two cases), and high maternal serum AFP (one case). Level II ultrasounds on all five fetuses were normal, and the abnormal cell line was never detected in fetal blood and/or cord blood. All five pregnancies were continued and had normal outcomes, with birth weights ranging from 2.4 to 3.8 kg. The development of all five children has been normal, with the oldest child in the study now 4 years of age. We suggest that the abnormal cell line in each case was of extrafetal origin, and that this may be one of the more common examples of this phenomenon, occurring in approximately 1/10000 prenatal diagnoses. Mosaicism i(20q) may have been missed in the past because of the higher resolution necessary to detect this subtle change.     

Biological and economic optima in a tropical grazing ecosystem in Australia

Our aim in this study was to identify the economically optimal level of use of resources for a grazing system in tropical Australia and to compare it with the biological optimum. Grazing management trials were conducted in the Ord River irrigation area of north-western Australia. Biologists at the Commonwealth Scientific and Industrial Research Organization provided the biological data. The liveweight gains of Kimberley shorthorn steers were recorded, after a 1-year fattening period, for different grazing management strategies. Five different stocking rates were used on irrigated pangola grass (Digitaria decumbens) fertilized with nitrogen at five different rates. All other were applied at fixed, non-limiting levels.The results of the trials were modelled by a liveweight gain production function. This production function was used in an income simulation model to identify economically optimal (profit maximizing) stocking rates. This was done in two stages. First, a base analysis was undertaken on the basis o the economic conditions prevailing in September 1987. Second, sensitivity analysis was applied to the results of the base analysis. The parameters varied were the rate of interest, store cattle prices, finished cattle prices, transport costs and the length of the planning horizon.The biological optimum, when defined as maximum liveweight gain ha⁻¹, corresponds to a much higher intensity of use of resources than the economic optimum, and yields substantially lower profits or higher losses. These discrepancies increase when economic conditions worsen, or when the planning horizon of graziers is decreased from 50 to 10 years. Therefore, the adoption of the biological optimum cannot result in an econonomically stable grazing system in the medium to long term, when it is highly likely that economic parameters will fluctuate. The economic stability of the system is increased, but is still quite weak, if the economically optimal input combination is utilized. It was not possible to determine whether this economic optimum would result in long-term ecological stability because the relevant data were not collected during the trials.The relevance of management recommendations made to graziers and land administrators would be increased if these recommendations were based on an analysis of both the economic and the ecological stability of grazing systems over the medium to long term. We show in the last part of this study how this could be accomplished.     

Prenatal diagnosis of cystinosis utilizing chorionic villus sampling

The prenatal diagnosis of cystinosis is currently based on the increased amount of free-cystine present in amniotic fluid cells. Amniocyte cultures must be grown for at least 2 weeks to obtain sufficient cells for such measurements. Thus, the diagnosis cannot be made until close to 20 weeks gestational age by this method. We report a case in which chorionic villi were used for direct cystine measurement resulting in the in utero diagnosis of cystinosis at 9 weeks gestational age. The diagnosis was confirmed by the study of cultured chorionic villus cells, and of the 10-week abortus.     

Evidence of a second gamete fusion after the first cleavage of the zygote in a 47,XX, + 18/70,XXX, + 18 mosaic. A remarkable diploid-triploid discrepancy after CVS

A 70,XXX, +18 karyotype was found by chorionic villus sampling, while the fetal fibroblast culture of the affected fetus revealed a 47,XX,+ 18 karyotype. From several possible mechanisms, we assume that a second gamete fusion occurred after the first cell division of the zygote. According to this interpretation, the mosaicism arose in very early pregnancy (at the two-cell stage). This discrepancy can therefore be explained by selection pressure, due to the differentiation processes in the embryonic tissues.     

Rapid prenatal diagnosis of Patau's syndrome in a fetus with an abdominal wall defect by 72 hour culture of cells from amniotic fluid

A woman in the 32nd week of pregnancy was referred for investigation because of fetal abnormalities, including an abdominal wall defect, detected by ultrasonography. In view of the increased risk of chromosome abnormality, amniocentesis was performed to enable informed decisions about the management of the pregnancy and delivery to be taken. Cells from the liquor were inoculated into standard lymphocyte culture medium and incubated for 72 h. Slides with a high mitotic index and good quality metaphases, comparable to those from a blood culture, were obtained after harvesting. Cytogenetic analysis showed the karyotype to be 46,XY,—14,+t(13ql4q), which is consistent with Patau's syndrome. This technique appears to be an option for rapid karyotyping in cases of abdominal wall defect, where a chromosomal abnormality is suspected.