Case-Only Design for GxE ExposureCasesControls Genotype:Non-carrierCarrierNon-carrierCarrier UnexposedabAB ExposedcdCD OR GxE estimators: –Case-control: (ad/bc) / (AD/BC) –Case-only:ad/bc Assuming no G-E association in controls Umbach et al Stat Med 1994;13:153-62 Smaller variance (more power) than case-control test Can't test this assumption in controls, then decide whether to do case-only or case-control Albert et al, AJE 2001:154:687-93 But can combine case-only and case-control estimators Mukerjee et al, GE 2008;32:615-26.
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