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. 2021 Apr 7;71(706):e347–e355. doi: 10.3399/BJGP.2020.0697

Table 3.

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.