No abstract

The cost-effectiveness of CF carrier screening depends greatly on couples' reproductive plans. CF carrier screening is most cost-effective when it is performed sequentially, when the information is used for more than one pregnancy, and when the intention of the couple is to identify and terminate affected pregnancies. These conclusions are important for policy considerations regarding population-based screening for CF, and may also have important implications for screening for less common diseases.

OBJECTIVES: This paper explores several critical assumptions and methodological issues arising in cost-effectiveness analyses of genetic screening strategies in the reproductive setting. METHODS: Seven issues that arose in the development of a decision analysis of alternative strategies for cystic fibrosis carrier screening are discussed. Each of these issues required a choice in technique. RESULTS: The presentations of these analyses frequently mask underlying assumptions and methodological choices. Often there is no best choice. In the case of genetic screening in the reproductive setting, these underlying issues often touch on deeply felt human values. CONCLUSIONS: Space limitations for published papers often preclude explaining such choices in detail; yet these decisions determine the way the results should be interpreted. Those who develop these analyses need to make sure that the implications of important assumptions are understood by the clinicians who will use them. At the same time, clinicians need to enhance their understanding of what these models truly mean and how they address underlying clinical, ethical, and economic issues.

No abstract

Very-low-frequency (VLF, 3-30 kHz) electromagnetic waves are prevalent in near-Earth space, and are produced by a variety of space-based and ground-based sources. Lightning and VLF transmitters launch powerful waves that propagate through the Earth's ionosphere and into the magnetosphere. Within the magnetosphere, naturally occurring and locally generated waves include chorus, hiss, and electromagnetic ion-cyclotron (EMIC) waves. Each of these whistler-mode waves propagating in the magnetospheric plasma can induce pitch-angle scattering and precipitation of trapped energetic particles (e.g. Inan & Carpenter, 1987;Imhof et al., 1983). For example, Abel and Thorne (1998) concluded that VLF waves radiated from both lightning and ground-based VLF transmitters play a significant role in maintaining the slot region of depleted fluxes between the inner and outer radiation belts. Each of these waves occurs in different regions of space, and with different amplitudes and frequencies, and therefore each affect somewhat different populations of energetic particles.The propagation of these VLF waves within the magnetosphere, as well as from the ground through the ionosphere, is complex and difficult to experimentally assess. Chorus and hiss waves, for example, are regularly measured by spacecraft such as the Van Allen Probes, but without knowledge of the source region of these waves, the propagation characteristics are difficult to characterize. Propagation characteristics such as the propagation direction, amplitude decay and/or growth, and reflections within the magnetosphere, are critical to understanding the quantitative effect these waves have on energetic particles.