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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)