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Table 4 Performance metrics of influenza clinical case definitions in subjects 6–49 years ( n= 523)

From: Determination of clinical and demographic predictors of laboratory-confirmed influenza with subtype analysis

  

Laboratory influenza

    
 

Clinical test

diagnosis

    

Clinical test

result

Positive

Negative

SN (%) (95% CI)

SP (%) (95% CI)

PPV (%) (95% CI)

NPV (%) (95% CI)

At least 1 criteriona

Positive

157

363

100.0 (undefined) b

0.8 (0.0–1.6)

30.2 (26.3–34.1)

100.0 (undefined) b

Negative

0

3

At least 2 criteriaa

Positive

149

292

94.9 (93.0–96.8)

20.2 (16.8–23.7)

33.8 (29.7–37.8)

90.2 (87.7–92.8)

Negative

8

74

At least 3 criteriaa

Positive

91

73

58.0 (53.7–62.2)

80.1 (76.6–83.5)

55.5 (51.2–59.7)

81.6 (78.3–84.9)

Negative

66

293

All 4 criteriaa

Positive

23

5

14.6 (11.6–17.7)

98.6 (97.6–99.6)

82.1 (78.9–85.4)

72.9 (69.1–76.7)

Negative

134

361

Exact 2 criteria c

Acute onset and fever

Positive

31

22

19.7 (16.3–23.2)

94.0 (92.0–96.0)

58.5 (54.3–62.7)

73.2 (69.4–77.0)

Negative

126

344

Acute onset and cough

Positive

86

85

54.8 (50.5–59.0)

76.8 (73.2–80.4)

50.3 (46.0–54.6)

79.8 (76.4–83.3)

Negative

71

281

Acute onset and body aches

Positive

64

68

40.8 (36.6–45.0)

81.4 (78.1–84.8)

48.5 (44.2–52.8)

76.2 (72.6–79.9)

Negative

93

298

Fever and cough

Positive

51

29

32.5 (28.5–36.5)

92.1 (89.8–94.4)

63.8 (59.6–67.9)

76.1 (72.4–79.7)

Negative

106

337

Fever and body aches

Positive

42

25

26.8 (23.0–30.5)

93.2 (91.0–95.3)

62.7 (58.5–66.8)

74.8 (71.1–78.5)

Negative

115

341

Cough and body aches

Positive

126

224

80.3 (76.8–83.7)

38.8 (34.6–43.0)

36.0 (31.9–40.1)

82.1 (78.8–85.4)

Negative

31

142

Cough + any of other 3 criteria

Positive

149

264

94.9 (93.0–96.8)

27.9 (24.0–31.7)

36.1 (32.0–40.2)

92.7 (90.5–95.0)

Negative

8

102

Exact 3 criteria c

Acute onset, fever, cough

Positive

31

14

19.7 (16.3–23.2)

96.2 (94.5–97.8)

68.9 (64.9–72.9)

73.6 (69.9–77.4)

Negative

126

352

Acute onset, cough, body aches

Positive

64

47

40.8 (36.6–45.0)

87.2 (84.3–90.0)

57.7 (53.4–61.9)

77.4 (73.8–81.0)

Negative

93

319

Acute onset, fever, body aches

Positive

23

9

14.6 (11.6–17.7)

97.5 (96.2–98.9)

71.9 (68.0–75.7)

72.7 (68.9–76.5)

Negative

134

357

Fever, cough, body aches

Positive

42

18

26.8 (23.0–30.5)

95.1 (93.2–96.9)

70.0 (66.1–74.0)

75.2 (71.5–78.9)

Negative

115

348

CDC ILI case definition d

Total study population

Positive

83

82

37.7 (33.6–41.9)

85.6 (82.6–88.6)

50.3 (46.0–54.6)

78.0 (74.5–81.6)

Negative

137

487

Subjects ages 3–5 years

Positive

3

15

25.0 (21.3–28.7)

71.7 (67.8–75.6)

16.7 (13.4–19.9)

80.9 (77.5–84.2)

Negative

9

38

Subjects ages 6–49 years

Positive

63

52

40.1 (35.9–44.3)

85.8 (82.8–88.8)

54.8 (50.5–59.0)

77.0 (73.4–80.6)

Negative

94

314

Subjects ages 50–80 years

Positive

17

15

33.3 (29.3–37.4)

90.0 (87.4–92.6)

53.1 (48.8–57.4)

79.9 (76.4–83.3)

Negative

34

135

  1. NOTE. CDC, Centers for Disease Control and Prevention; CI, confidence interval; ILI, influenza-like illness; NPV, negative predictive value; PPV, positive predictive value; SN, sensitivity; SP, specificity. The first 15 clinical tests displayed are defined according to combinations of 4 influenza predictors (“criteria”) present in a subject: acute onset, fever, cough, and body aches. CI calculated for a proportion estimate as follows: (estimate) ± 1.96 x √(estimate x (1 – estimate)/n). aPositive test defined by at least n of the 4 criteria of interest being met. bCI undefined; cannot be calculated for a proportion of 1.0. cThe exact criteria listed are met, regardless of whether the other unlisted criteria are met. dCDC ILI definition = temperature ≥37.8 °C and either cough or sore throat in absence of another known cause. Presence of another known cause is not assessable in this study. This case definition’s performance was evaluated in and is reported for all age groups included in the study.