Table 3. Detection Probabilities for High-Risk Variants.

Selection
Single gene model
All Individuals	0.010	0.010	0.010	0.010
Cases	0.015	0.020	0.029	0.048
w/affected sibs	0.019	0.029	0.057	0.130
sharing 1 or 2 IBD	0.020	0.032	0.066	0.155
sharing 2 IBD	0.022	0.039	0.083	0.201
With a second, nuisance locus
All Individuals	0.010	0.010	0.010	0.010
Cases	0.014	0.019	0.028	0.045
w/affected sibs	0.017	0.026	0.049	0.109
sharing 1 or 2 IBD	0.018	0.029	0.056	0.130
sharing 2 IBD	0.020	0.034	0.070	0.169

In each scenario there is a sporadic disease rate of 1% and the high-risk allele of interest elevates the disease risk by a factor of , which varies across columns. The rows represent increasingly restrictive sampling rules, and the probability that the high risk allele is present (one or two copies) in a sampled proband is tabulated. In the upper half of the table, risk depends only on one locus. In the lower half, there is also a nuisance locus, with a 5 percent allele frequency, i.e. 10 times as common as the allele of interest, and additive with its effect.