Table 2. Characteristics of Enrolled Patients.
| Characteristic | Total, n (%) | D-dimer Negative, n (%) | D-dimer Positive, n (%) | Ratio of False- to True-positive D-dimers |
|---|---|---|---|---|
| Enrolled | 4,356 (100) | 2,453 (56) | 1,903 (44) | 7.8 |
| Female | 2,930 (67) | 1,320 (45) | 1,610 (55) | 9.5 |
| Age (yr) | ||||
| <30 | 605 (14) | 373 (62) | 232 (38) | 14.5 |
| 30–39 | 961 (22) | 642 (67) | 319 (33) | 8.4 |
| 40–49 | 954 (22) | 619 (65) | 335 (35) | 8.6 |
| 50–59 | 798 (18) | 468 (59) | 330 (41) | 6.3 |
| 60–69 | 507 (12) | 217 (43) | 290 (57) | 8.1 |
| 70–79 | 328 (8) | 100 (30) | 228 (70) | 6.4 |
| ≥80 | 203 (5) | 34 (17) | 169 (83) | 5.8 |
| Race/ethnicity | ||||
| Black or African American | 1,474 (34) | 753 (51) | 721 (49) | 8.2 |
| Hispanic | 238 (5) | 155 (65) | 83 (35) | 40.5 |
| White | 2,500 (57) | 1,454 (58) | 1,046 (42) | 6.9 |
| Other | 144 (3) | 91 (63) | 53 (37) | 9.6 |
| Pretest probability of PE* | ||||
| Low (<15%) | 3,224 (74) | 1,206 (37) | 2,018 (63) | 14.1 |
| Intermediate (15%–40%) | 933 (21) | 561 (60) | 372 (40) | 5.6 |
| High (>40%) | 191 (4) | 132 (69) | 59 (31) | 1.5 |
| BMI | ||||
| <25 | 1,517 (35) | 871 (57) | 646 (43) | 9.4 |
| 25–29.9 | 1,240 (28) | 695 (56) | 545 (44) | 7.5 |
| 30–34.9 | 790 (18) | 447 (57) | 343 (43) | 7.4 |
| ≥35 | 809 (19) | 440 (54) | 369 (46) | 6.4 |
| Cocaine use | 68 (2) | 31 (46) | 37 (54) | 17.5 |
| Family history of PE | 538 (12) | 331 (62) | 207 (38) | 4.9 |
| Immobility | ||||
| General | 243 (6) | 71 (29) | 172 (71) | 4.9 |
| Limb | 73 (2) | 21 (29) | 52 (71) | 3.3 |
| Neurologic | 26 (1) | 8 (31) | 18 (69) | 8.0 |
| Hemoptysis | 116 (3) | 45 (39) | 71 (61) | 10.8 |
| Medication use | ||||
| Antiplatelet | 652 (15) | 290 (44) | 362 (56) | 6.9 |
| Estrogen | 400 (9) | 249 (62) | 151 (38) | 5.3 |
| Warfarin | 178 (4) | 84 (47) | 94 (53) | 5.7 |
| Past medical history | ||||
| Anxiety | 548 (13) | 335 (61) | 213 (39) | 10.2 |
| CAD | 416 (10) | 152 (37) | 264 (63) | 10.5 |
| Cerebrovascular disease | 151 (3) | 67 (44) | 84 (56) | 15.8 |
| CHF | 287 (7) | 99 (34) | 188 (66) | 8.0 |
| Connective tissue disease | ||||
| Rheumatoid arthritis | 76 (2) | 30 (39) | 46 (61) | 22.0 |
| Systemic lupus erythematosis | 53 (1) | 22 (42) | 31 (58) | 9.3 |
| Other connective tissue disease | 26 (1) | 11 (42) | 15 (58) | 4.0 |
| Diabetes | 556 (13) | 243 (44) | 313 (56) | 9.4 |
| Hemodialysis | 38 (1) | 12 (32) | 26 (68) | 25 |
| Hypertension | 1,503 (35) | 696 (46) | 807 (54) | 7.9 |
| Lung disease | ||||
| Asthma | 478 (11) | 292 (61) | 186 (39) | 15.9 |
| COPD | 273 (6) | 107 (39) | 166 (61) | 10.1 |
| Malignancy | ||||
| Active | 203 (5) | 59 (29) | 144 (71) | 4.5 |
| Inactive | 211 (5) | 95 (45) | 116 (55) | 7.3 |
| Sickle cell disease or trait | 15 (0) | 1 (7) | 14 (93) | 13.0 |
| Thrombophilia | 45 (1) | 24 (53) | 21 (47) | 4.3 |
| VTE | ||||
| Under treatment | 118 (3) | 56 (47) | 62 (53) | 2.9 |
| Not under treatment | 258 (6) | 118 (46) | 140 (54) | 4.6 |
| Pregnancy | ||||
| First trimester | 18 (0) | 8 (44) | 10 (56) | —† |
| Second trimester | 31 (1) | 7 (23) | 24 (77) | — |
| Third trimester | 23 (1) | 1 (4) | 22 (96) | — |
| Postpartum | 65 (1) | 19 (29) | — | — |
| Smoking | 1,635 (38) | 905 (55) | 730 (45) | 11.0 |
| Surgery | ||||
| Abdominal | 72 (2) | 18 (25) | 54 (75) | 5.8 |
| Chest | 34 (1) | 10 (29) | 24 (71) | 11.0 |
| Orthopedic | 49 (1) | 15 (31) | 34 (69) | 2.8 |
| Other | 37 (1) | 11 (30) | 26 (70) | — |
| Trauma | 36 (1) | 17 (47) | 19 (53) | 8.5 |
| Travel | 398 (9) | 261 (66) | 137 (34) | 6.2 |
BMI = body mass index; CAD = coronary artery disease (a history of angina, myocardial infarction, or coronary artery revascularization procedure); CHF = congestive heart failure; COPD = chronic obstructive pulmonary disease; PE = pulmonary embolism; VTE = venous thromboembolism (deep vein thrombosis or PE).
*
Pretest probability determined by treating physician.
†
No patients who had D-dimer performed were diagnosed with PE.