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Table 1 Distribution of test results in the full study population and the nested case-control samples with various case-control ratios

From: Advantages of the nested case-control design in diagnostic research

 

Full study population

Nested case-control samples for different case-control ratios

 

DVT +

DVT-

Cases

Controls

Test results

n = 289

n = 1006

n = 289

1:1

n = 289

1:2

n = 578

1:3

n = 867

1:4

n = 1156

D-dimer test abnormal

271 (94)

621 (62)

271 (94)

178 (61)

357 (62)

535 (62)

713 (62)

Calf difference, cm*

3.2 (1.7)

2.1 (1.6)

3.2 (1.7)

2.1 (1.6)

2.1 (1.6)

2.1 (1.6)

2.1 (1.6)

Age, years*

61.9 (16.8)

59.4 (17.7)

61.9 (16.8)

59.4 (17.8)

59.5 (17.8)

59.4 (17.8)

59.4 (17.7)

Male gender

137 (47)

330 (33)

137 (47)

94 (33)

190 (33)

282 (33)

380 (33)

  1. For each case-control ratio, 100 nested case-control samples were drawn. The statistics of the control samples are the average values. All values represent absolute patient numbers (%) unless stated otherwise.
  2. DVT+ = deep vein thrombosis present; DVT- = deep vein thrombosis absent; *mean (standard deviation)