Table 5.
Sensitivity, specificity and predictive values of different case definitions for detection of influenza among hospitalized patients of all ages, Ballabgarh, India, July 2009–August 2011
| No. (%) of patients | Sensitivity % (95% CI) | Specificity % (95% CI) | Positive predictive value % (95% CI) | Negative predictive value % (95% CI) | |||
|---|---|---|---|---|---|---|---|
| All patients (n = 1043) | Influenza virus + (n = 74) | Influenza virus − (n = 969) | |||||
| ≥1 respiratory symptom | 913 (88) | 70 | 843 | 95 (87, 99) | 13 (11, 15) | 7 (6, 7) | 97 (92, 99) |
| Acute respiratory infection | 594 (57) | 65 | 529 | 88 (78, 94) | 45 (42, 49) | 11 (8, 14) | 98 (96, 99) |
| Influenza‐like illness | 180 (17) | 33 | 147 | 45 (33, 57) | 85 (82, 87) | 18 (13, 25) | 95 (94, 97) |
| Severe acute respiratory illness* | 179 (17) | 21 | 158 | 28 (19, 40) | 84 (81, 86) | 12 (7, 17) | 94 (92, 95) |
| Febrile acute respiratory illness | 185 (18) | 33 | 152 | 45 (33,57) | 84 (82, 87) | 18 (13, 24) | 95 (94, 96) |
| Additional Case Definitions that include reported fever and case definitions based on symptom complexes | |||||||
| Influenza‐like illness: measured or reported fever | 448 (43) | 58 | 390 | 78 (67, 87) | 60 (57, 63) | 13 (10, 16) | 97 (96, 99) |
| Severe acute respiratory illness: measured or reported fever* | 243 (23) | 27 | 216 | 37 (26, 49) | 78 (75, 80) | 11 (8, 16) | 94 (92, 96) |
| Febrile acute respiratory illness: measured or reported fever | 478 (46) | 61 | 417 | 82 (72, 90) | 57 (54, 60) | 13 (10, 16) | 98 (96, 99) |
| Measured fever plus cough | 169 (16) | 30 | 139 | 41 (29, 53) | 86 (83, 88) | 18 (12, 24) | 95 (93, 96) |
| Measured or reported fever plus cough | 430 (41) | 55 | 375 | 74 (63, 84) | 61 (58, 64) | 13 (10, 16) | 97 (95,98) |
| Measured fever plus either cough or nasal discharge | 173 (17) | 30 | 143 | 41 (29, 53) | 85 (83, 87) | 17 (12, 24) | 95 (93, 93) |
| Measured or reported fever plus either cough or nasal discharge | 446 (43) | 57 | 389 | 77 (66, 86) | 60 (57, 63) | 13 (10, 16) | 97 (96, 98) |
*Age‐specific definitions as noted in Table 1 were used. The requirement of fever (measured or measured/reported) was included only for persons 5 years of age and older.