Table 4.

Performance of Clinical Prediction Rules and Simple Heuristics for the Diagnosis of Influenza

Derivation groupValidation groupAll patients
Flu/Total (%)LRIn Group (%)Flu/Total (%)LRIn Group (%)Flu/Total (%, 95% CI)LRIn Group (%)
Flu score 1
    Low risk (0–11)7/86 (8.1)0.1726.41/34 (2.9)0.0625.68/120 (6.7, 3.4–12.6)0.1426.1
    Moderate risk (12–15)24/106 (22.6)0.5732.516/46 (34.8)0.9834.640/152 (26.3, 20.0–33.8)0.6933.1
    High risk (16–24)79/134 (59.0)2.8241.130/53 (56.6)2.3939.8109/187 (58.3, 51.1–65.1)2.6940.7
Flu score 2
    Low risk (0–2)6/77 (7.8)0.1723.61/32 (3.1)0.0624.17/109 (6.4, 3.1–12.7)0.1323.7
    Moderate risk (4–6)44/149 (29.5)0.8245.716/56 (28.6)0.7342.160/205 (29.3, 23.5–35.8)0.8044.7
    High risk (8–12)60/100 (60.0)2.9530.730/45 (66.7)3.6633.890/145 (62.1, 54.0–69.6)3.1531.6
Flu score 3
    Low risk (0–2)10/109 (9.2)0.2033.42/40 (5.0)0.1030.112/149 (8.1, 4.7–13.5)0.1732.5
    Moderate risk (3)25/90 (27.8)0.7627.614/39 (35.9)1.0229.339/129 (30.2, 23.0–38.6)0.8328.1
    High risk (4–6)75/127 (59.1)2.8339.031/54 (57.4)2.4740.6106/181 (58.6, 51.3–65.5)2.7239.4
Flu score 4
    Low risk (−1–3)4/36 (11.1)0.2511.11/19 (5.3)0.1014.35/55 (9.1, 4.0–19.6)0.1912.0
    Moderate risk (4–8)36/166 (21.7)0.5551.217/65 (26.2)0.6548.953/231 (22.9, 18.0–28.8)0.5750.5
    High risk (9–11)69/122 (56.6)2.5737.729/49 (59.2)2.6536.898/171 (57.1, 49.8–64.5)2.5937.4
Flu score 5
    Low risk (0–11)3/28 (10.7)0.248.60/17 (0.0)0.012.83/45 (6.7, 2.3–17.9)0.149.8
    Moderate risk (12–16)59/220 (26.8)0.7267.926/84 (31.0)0.8263.285/304 (28.0, 23.2–33.3)0.7566.5
    High risk (17+)47/76 (61.8)3.2023.521/32 (65.6)4.2724.168/108 (63.0, 53.6–71.5)3.2823.6
Heuristics
    Fever, cough
        Positive (both present)NANA96/157 (61.1, 53.4–68.4)3.0334.2
        Negative (0 or 1 present)NANA61/302 (20.2, 16.1–25.1)0.4965.8
    Fever, cough, and acute-onset
        Positive (all 3 present)NANA64/86 (74.4, 64.3–82.5)5.5918.7
        Negative (0, 1, or 2 present)NANA93/373 (24.9, 20.8–29.6)0.6481.3