Comparison of different diagnostic approaches in the validation cohort (after performing imputation)a
| Variable | Pr, %b | Sensitivity, % (95% CI) | Specificity, % (95% CI) | LR+ (95% CI) | LR– (95% CI) | PPV, % (95% CI) | NPV, % (95% CI) |
|---|---|---|---|---|---|---|---|
| Symptoms | |||||||
| Back pain | NA | 21.5 (16.5 to 27.2) | 91.2 (91.1 to 91.3) | 2.4 (1.9 to 3.1) | 0.86 (0.81 to 0.92) | 0.13 (0.10 to 0.17) | 99.95 (99.94 to 99.96) |
| Rib pain | NA | 1.2 (0.3 to 3.6) | 99.5 (99.5 to 99.5) | 2.5 (0.8 to 7.7) | 0.99 (0.99 to 1.0) | 0.14 (0.01 to 0.29) | 99.94 (99.94 to 99.95) |
| Chest pain | NA | 9.1 (5.8 to 13.4) | 93.6 (93.6 to 93.7) | 1.4 (0.9 to 2.1) | 0.97 (0.93 to 1.0) | 0.08 (0.05 to 0.11) | 99.95 (99.94 to 99.95) |
| Nosebleeds | NA | 1.2 (0.3 to 3.6) | 99.2 (99.2 to 99.2) | 1.6 (0.5 to 4.9) | 0.99 (0.98 to 1.0) | 0.09 (0.01 to 0.18) | 99.94 (99.94 to 99.95) |
| FBC (index test) | |||||||
| Anaemia (any type) | NA | 55.6 (48.6 to 62.5) | 83.6 (83.5 to 83.7) | 3.4 (3.2 to 3.6) | 0.53 (0.39 to 0.67) | 0.18 (0.15 to 0.21) | 99.97 (99.96 to 99.98) |
| Normocytic anaemia | NA | 43.5 (37.0 to 50.0) | 85.1 (84.9 to 85.2) | 2.9 (2.7 to 3.2) | 0.66 (0.54 to 0.77) | 0.15 (0.13 to 0.19) | 99.96 (99.95 to 99.97) |
| Macrocytic anaemia | NA | 11.9 (8.1 to 15.8) | 98.5 (98.4 to 98.6) | 8.1 (6.3 to 9.8) | 0.89 (0.84 to 0.95) | 0.43 (0.26 to 0.61) | 99.95 (99.94 to 99.96) |
| Low platelets | NA | 8.3 (5.5 to 11.1) | 96.5 (96.4 to 96.6) | 2.4 (1.9 to 2.9) | 0.95 (0.91 to 0.98) | 0.13 (0.07 to 0.18) | 99.95 (99.94 to 99.96) |
| Low WCC | NA | 7.0 (4.5 to 9.6) | 96.9 (96.9 to 97.0) | 2.3 (1.7 to 2.9) | 0.96 (0.93 to 0.99) | 0.13 (0.06 to 0.19) | 99.94 (99.94 to 99.95) |
| High MCV | NA | 22.9 (17.5 to 28.4) | 91.6 (91.5 to 91.7) | 2.8 (2.3 to 3.2) | 0.84 (0.76 to 0.92) | 0.15 (0.10 to 0.19) | 99.95 (99.94 to 99.96) |
| Other tests | |||||||
| Hypercalcemia | NA | 5.7 (1.9 to 9.6) | 98.3 (98.2 to 98.4) | 3.4 (1.3 to 5.5) | 0.96 (0.91 to 1.0) | 0.19 (0.04 to 0.33) | 99.95 (99.94 to 99.96) |
| High ESR | NA | 80.3 (70.4 to 90.3) | 54.8 (54.5 to 55.1) | 1.7 (1.6 to 1.9) | 0.35 (0.08 to 0.63) | 0.10 (0.08 to 0.11) | 99.98 (99.97 to 99.99) |
| High ESR or anaemia | NA | 90.5 (81.4 to 99.5) | 50.0 (49.8 to 50.3) | 1.8 (1.7 to 1.9) | 0.19 (0.13 to 0.28) | 0.10 (0.08 to 0.12) | 99.99 (99.98 to 99.99) |
| High ESR and anaemia | NA | 45.5 (38.9 to 51.9) | 88.4 (88.2 to 88.5) | 3.9 (3.6 to 4.2) | 0.62 (0.50 to 0.74) | 0.20 (0.17 to 0.25) | 99.96 (99.96 to 99.97) |
| FBC model | |||||||
| 77th percentilec | 0.06 | 78.9 (73.2 to 83.9) | 77.2 (77.1 to 77.3) | 3.5 (3.2 to 3.7) | 0.27 (0.21 to 0.35) | 0.19 (0.16 to 0.22) | 99.98 (99.97 to 99.98) |
| 90th percentile | 0.12 | 61.6 (55.1 to 67.7) | 90.2 (90.1 to 90.3) | 6.3 (5.7 to 6.9) | 0.43 (0.36 to 0.50) | 0.34 (0.29 to 0.40) | 99.98 (99.97 to 99.98) |
| 95th percentile | 0.20 | 41.3 (35.1 to 47.8) | 95.1 (95.0 to 95.2) | 8.4 (7.3 to 9.8) | 0.62 (0.55 to 0.69) | 0.46 (0.37 to 0.55) | 99.96 (99.96 to 99.97) |
| 99th percentile | 0.60 | 18.2 (13.5 to 23.6) | 99.1 (99.1 to 99.1) | 19.9 (15.2 to 26.1) | 0.83 (0.78 to 0.88) | 1.10 (0.80 to 1.40) | 99.95 (99.95 to 99.96) |
| 99.5th percentile | 0.90 | 12.8 (8.9 to 17.7) | 99.5 (99.5 to 99.6) | 27.6 (19.8 to 38.4) | 0.88 (0.84 to 0.92) | 1.50 (1.00 to 2.10) | 99.95 (99.95 to 99.96) |
| 99.9th percentile | 2.20 | 4.1 (2.0 to 7.5) | 99.9 (99.9 to 99.9) | 42.4 (23.5 to 82.9) | 0.96 (0.94 to 0.99) | 2.30 (1.10 to 4.10) | 99.95 (99.94 to 99.95) |
| All-test model | |||||||
| 84th percentilec | 0.06 | 82.6 (77.3 to 87.2) | 83.9 (83.8 to 84.0) | 5.1 (4.8 to 5.4) | 0.21 (0.16 to 0.27) | 0.28 (0.24 to 0.32) | 99.98 (99.98 to 99.99) |
| 90th percentile | 0.09 | 71.9 (65.8 to 77.5) | 90.3 (90.2 to 90.4) | 7.4 (6.9 to 8.0) | 0.31 (0.25 to 0.38) | 0.40 (0.34 to 0.47) | 99.98 (99.97 to 99.98) |
| 95th percentile | 0.15 | 62.4 (56.8 to 68.5) | 95.1 (95.0 to 95.1) | 12.9 (11.7 to 14.2) | 0.40 (0.34 to 0.47) | 0.70 (0.59 to 0.81) | 99.98 (99.97 to 99.98) |
| 99th percentile | 0.45 | 34.3 (28.3 to 40.6) | 99.0 (99.0to 99.1) | 35.1 (29.4 to 41.9) | 0.66 (0.61 to 0.73) | 1.9 (1.5 to 2.3) | 99.96 (99.96 to 99.97) |
| 99.5th percentile | 0.70 | 24.0 (18.7 to 29.9) | 99.5 (99.5 to 99.5) | 48.9 (38.9 to 61.4) | 0.76 (0.71 to 0.82) | 2.6 (2.0 to 3.3) | 99.96 (99.95 to 99.96) |
| 99.9th percentile | 1.90 | 7.8 (4.8 to 12.0) | 99.9 (99.9 to 99.9) | 80.5 (51.8 to 125.0) | 0.92 (0.89 to 0.96) | 4.2 (2.5 to 6.4) | 99.95 (99.94 to 99.95) |
↵a Results presented are based on multiple imputation as described in the methods section.
↵b Pr = corresponding probability (%) of the selected risk score percentile.
↵c These percentile values were selected to match the background prevalence in the whole cohort. ESR = erythrocyte sedimentation rate. FBC = full blood count. LR– = negative likelihood ratio. LR+ = positive likelihood ratio. MCV = mean corpuscular volume. NA = not applicable. NPV = negative predictive value. PPV = positive predictive value. WCC = white cell count.