Patient demographics and risk characteristics
| Usual rule-out strategy (n=313) | LoDED strategy (n=316) | All patients (n=629) | |
| Age (years), mean (SD) | 53.6 (16.2) | 54.0 (16.2) | 53.8 (16.1) |
| Sex | |||
| Women (%) | 127 (41) | 129 (41) | 256 (41) |
| Men (%) | 186 (59) | 187 (59) | 373 (59) |
| Ethnic origin (%)* | |||
| White | 277 (89) | 277 (88) | 554 (88) |
| Chest pain history (clinician reported)† (%) | |||
| Slightly suspicious | 176 (56) | 171 (54) | 347 (55) |
| Moderately suspicious | 112 (36) | 111 (35) | 223 (36) |
| Highly suspicious | 25 (8) | 34 (11) | 59 (9) |
| Prior history of coronary artery disease (%) | 41 (13) | 40 (13) | 81 (13) |
| Known risk factors (%) | |||
| Hypercholesterolaemia | 48 (15) | 55 (17) | 103 (16) |
| Hypertension | 86 (28) | 82 (26) | 168 (27) |
| Diabetes (treated) | 31 (10) | 34 (11) | 65 (10) |
| Current smoking | 54 (17) | 54 (17) | 108 (17) |
| Family history of coronary artery disease (first-degree relative under the age of 65 years) | 67 (21) | 71 (23) | 138 (22) |
| TIMI score,‡ median (IQR) | 0 (0–1) | 0 (0–1) | 0 (0–1) |
| TIMI score 0 (%) | 175 (57.6) | 176 (57.3) | 351 (57.5) |
| TIMI score 1 (%) | 60 (19.7) | 63 (20.5) | 123 (20.1) |
| TIMI score ≥2 (%) | 69 (22.7) | 68 (22.2) | 137 (22.4) |
| HEART score,§ median (IQR) | 2 (1–4) | 2 (1–4) | 2 (1–4) |
| HEART score 0–3 (%) | 213 (71) | 211 (69) | 424 (70) |
| HEART score 4–6 (%) | 75 (25) | 83 (27) | 128 (26) |
| HEART score ≥7 (%) | 13 (4) | 11 (4) | 24 (4) |
| Chest pain onset to arrival in ED (hours), median (IQR) | 2.5 (1.6–3.9) | 2.2 (1.4–3.4) | 2.3 (1.5–3.6) |
| Chest pain onset to arrival in ED (hours) (range)¶ | 0.02–178.4 | 0.02–120.5 | 0.02–178.4 |
| Chest pain onset to first hs-cTn sample collection (hours) (median (IQR)) | 3.3 (2.4–4.7) | 3.2 (2.2–4.5) | 3.3 (2.3–4.5) |
| Chest pain onset to first hs-cTn sample collection (hours) (range)¶ | 0.2–178.6 | 0.5–121.4 | 0.2–178.6 |
| Chest pain onset to first hs-cTn sample collection categorised by minutes (%) | |||
| 0–60 min | 9 (3) | 4 (1) | 13 (2) |
| 61–120 min | 34 (12) | 54 (18) | 88 (15) |
| 121–180 min | 85 (29) | 76 (26) | 161 (28) |
| >181 min | 161 (56) | 162 (55) | 323 (55) |
*Data missing for one patient.
†Clinicians were asked to grade level of suspicion after taking a history according to definitions used within the HEART score (see further).26 A highly suspicious history included all of central chest discomfort with radiation to the jaw/arms precipitated by exertion and relieved by rest or nitrates. A moderately suspicious history included some highly suspicious features but will have some other atypical features, such as right-sided pain, burning pain or pain that is worse on deep inspiration. A slightly suspicious history did not have any highly suspicious features but by definition of being involved in the trial, the treating clinician felt the patient warranted testing to rule out a cardiac cause for chest pain.
‡TIMI score.29 Data available in 611/629 cases.
§HEART: data available in 606/629 cases.26
¶Refers to chest pain onset time, rather than peak symptoms. Note patients were excluded if peak symptoms occurred >6 hours prior to ED presentation.
ED, emergency department; HEART, History, ECG, Age, Risk factors, Troponin; hs-cTn, high-sensitivity cardiac troponin; LoDED, limit of detection and ECG discharge; TIMI, Thrombolysis In Myocardial Infarction.