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Table 1 Scenario for Example 1

From: Flexible Two-Phase studies for rare exposures: Feasibility, planning and efficiency issues of a new variant

Variables and parameters characterizing the set-up

Values of parameters and variables

Stratification/Proxy Z (with J strata)

Past work in metal industry

 

No: Z = 1

 

Yes: Z = 2

Phase One prevalence among controls (Ï„0 j)

Z = 1: Ï„0 1 = 80%

 

Z = 2: Ï„0 2 = 20%*

Risk factor X (with K outcomes)

Exposure to MWF

 

No: X = 1

 

Yes: X = 2

Disease Model (Odds Ratios) (ψk)

ψ1 = 1: baseline risk

 

ψ2 = 2#

Phase Two prevalence of X among controls by stratum (Ï€0 jk)

Z = 1: π0 11 = 97.5%, π0 12 = 2.5%&

Z = 2: π0 21 = 75%, π0 22 = 25%@

  1. *20% prevalence of having worked in the metal industry
  2. #Exposure to MWF doubles the risk of bladder cancer
  3. &Among non-metal-industry workers, 2.5% exposed to MWF
  4. @Among metal-industry workers, 25% exposed to MWF
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Epidemiologic Perspectives & Innovations

ISSN: 1742-5573