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Table 2 Impact of main effects on type I error and analytical bias for the case-only design

From: The case-only design is a powerful approach to detect interactions but should be used with caution

  

Disease prevalence

\({{\varvec{\beta}}}_{{\varvec{G}}}\)

\({{\varvec{\beta}}}_{{\varvec{E}}}\)

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

4.5%

5.0%

10.0%

15.0%

20.0%

(a) Type I error

\(\ln(3.846)\) 

\(\ln(5)\)

0.141321

0.252332

0.396712

0.551859

0.695653

0.810552

0.891836

0.942837

0.972389

0.999998

1.000000

1.000000

\(\ln(3.846)\)

\(\ln(2)\)

0.056403

0.063479

0.072751

0.085891

0.101210

0.119065

0.138098

0.160377

0.183840

0.480285

0.735506

0.873881

\(\ln(1.2)\) 

\(\ln(2)\)

0.050132

0.050603

0.049854

0.050842

0.050614

0.051195

0.051387

0.052100

0.052221

0.057378

0.063536

0.070049

\(\ln(1.05)\) 

\(\ln(1.1)\)

0.049890

0.049729

0.049665

0.049657

0.049644

0.049992

0.049896

0.049923

0.050019

0.050016

0.049992

0.049666

\(\ln(0.952)\) 

\(\ln(0.909)\)

0.049816

0.049991

0.049856

0.049738

0.049618

0.050020

0.050054

0.049950

0.049860

0.049651

0.049931

0.050423

\(\ln(0.833)\) 

\(\ln(0.5)\)

0.050030

0.049658

0.049459

0.049875

0.049607

0.049515

0.049339

0.049723

0.049573

0.049940

0.051270

0.052579

\(\ln(0.26)\) 

\(\ln(0.5)\)

0.048962

0.048521

0.048793

0.048931

0.049388

0.049655

0.050008

0.050319

0.051327

0.063964

0.088547

0.125843

\(\ln(0.26)\)

\(\ln(0.2)\)

0.047237

0.047101

0.046880

0.047278

0.047025

0.047459

0.047611

0.048081

0.048999

0.063687

0.096078

0.152817

(b) Analytical bias

\(\ln(3.846)\)

\(\ln(5)\)

−0.039119

−0.057894

−0.076150

−0.093890

−0.111119

−0.127843

−0.144066

−0.159797

−0.175042

−0.302652

−0.391307

−0.449137

\(\ln(3.846)\)

\(\ln(2)\)

−0.012563

−0.018684

−0.024697

−0.030605

−0.036407

−0.042105

−0.047698

−0.053188

−0.058576

−0.106964

−0.145864

−0.175993

\(\ln(1.2)\)

\(\ln(2)\)

−0.001667

−0.002479

−0.003277

−0.004061

−0.004831

−0.005588

−0.006330

−0.007060

−0.007775

−0.014227

−0.019476

−0.023631

\(\ln(1.05)\)

\(\ln(1.1)\)

.−0.000048

−0.000072

−0.000095

−0.000118

−0.000141

−0.000164

−0.000186

−0.000208

−0.000230

−0.000434

−0.000612

−0.000764

\(\ln(0.952)\) 

\(\ln(0.909)\)

−0.000044

−0.000066

−0.000087

−0.000109

−0.000130

−0.000151

−0.000171

−0.000192

−0.000212

−0.000404

−0.000574

−0.000724

\(\ln(0.833)\)

\(\ln(0.5)\)

−0.000928

−0.001389

−0.001847

−0.002303

−0.002756

−0.003207

−0.003655

−0.004101

−0.004544

−0.008831

−0.012836

−0.016536

\(\ln(0.26)\)

\(\ln(0.5)\)

−0.005304

−0.007952

−0.010597

−0.013240

−0.015878

−0.018514

−0.021146

−0.023774

−0.026399

−0.052388

−0.077767

−0.102296

\(\ln(0.26)\)

\(\ln(0.2)\)

−0.008789

−0.013196

−0.017611

−0.022035

−0.026467

−0.030907

−0.035354

−0.039810

−0.044273

−0.089276

−0.134820

−0.180639

  1. Data (N = 10,000 cases) were generated under the null with no interaction (\({\beta }_{G\times E}=0\)). The MAF for the genetic variant is 0.2 and the frequency of the environmental exposure is 0.1. Type I error is calculated as the proportion of instances that the null hypothesis is rejected among all 1,000,000 replicates (\(\alpha =0.05)\). Analytical bias was calculated using formula (4). Type I errors exceeding 5% of the alpha level are highlighted in bold in the table