Bulletin of the World Health Organization

Performance of case definitions used for influenza surveillance among hospitalized patients in a rural area of India

Siddhivinayak Hirve, Mandeep Chadha, Pallavi Lele, Kathryn E Lafond, Avinash Deoshatwar, Somnath Sambhudas, Sanjay Juvekar, Anthony Mounts, Fatimah Dawood, Renu Lal & Akhilesh Mishra

Volume 90, Number 11, November 2012, 804-812

Table 4. Performance of standard case definitions and sign/symptom combinations in the identification of influenza among hospitalized patients, Vadu, India, May 2009–April 2011

Definition, by patient age Value (%) and 95% confidence interval
Sensitivity Specificity Positive predictive valuea Negative predictive valuea
Age < 5 years (n = 337)
Severe acute respiratory illness (measured fever only) 11 (4.2–24.7) 87 (82.2–90.3) 11 (4.5–25.9) 86 (80.6–89.6)
Severe acute respiratory illness (reported or measured fever) 11 (4.2–24.7) 86 (81.4–89.6) 11 (4.1–24.1) 86 (80.9–89.8)
Influenza-like illness (measured fever only) 69 (53.5–81.4) 43 (37.4–49.0) 17 (11.9–23.5) 90 (83.0–94.0)
Influenza-like illness (reported or measured fever) 87 (73.2–94.4) 5 (3.2–8.5) 13 (9.2–17.3) 72 (49.1–87.5)
Acute respiratory illness 77 (61.6–87.3) 26 (21.2–31.4) 14 (10.1–19.4) 88 (78.2–93.3)
Febrile acute respiratory illness (measured fever only) 63 (47.8–75.6) 44 (38.1–49.4) 16 (11.3–22.5) 88 (81.0–92.3)
Febrile acute respiratory illness (reported or measured fever) 77 (61.6–87.3) 27 (21.9–32.1) 14 (10.1–19.6) 88 (78.7–93.5)
Individual symptoms and symptom combinations
    Reported or measured fever 95 (83.1–98.5) 3 (1.4–5.5) 14 (10.1–18.3) 78 (45.2–93.6)
    Measured fever (> 38 °C) 88 (75.5–94.9) 21 (16.3–25.6) 16 (12.2–21.7) 92 (81.9–96.3)
    Cough 77 (61.6–87.3) 33 (27.3–38.1) 15 (10.9–21.1) 90 (81.8–94.5)
    Sore throat 51 (36.2–66.1) 53 (47.3–58.8) 16 (10.2–22.7) 88 (81.7–92.0)
    Shortness of breath 11 (4.2–24.7) 86 (81.1–89.4) 10 (4.0–23.5) 86 (80.9–89.8)
    Cough and reported or measured fever 77 (61.6–87.3) 33 (28.1–39.1) 16 (11.3–21.7) 90 (82.0–94.6)
    Sore throat and reported or measured fever 51 (36.2–66.1) 54 (47.7–59.2) 16 (10.4–23.0) 88 (81.7–92.0)
Age ≥ 5 years (n = 2842)
Severe acute respiratory illness (measured fever only) 3 (1.7–4.5) 98 (97.4–98.7) 39 (25.6–54.2) 72 (70.2–74.1)
Severe acute respiratory illness (reported or measured fever) 4 (2.5–5.7) 97 (96.4–97.9) 35 (24.3–47.2) 72 (70.1–74.1)
Influenza-like illness (measured fever only) 70 (66.3–73.5) 53 (50.7–54.9) 34 (31.6–36.9) 84 (81.2–85.6)
Influenza-like illness (reported or measured fever) 97 (95.2–98.0) 3 (2.3–3.7) 26 (24.1–27.7) 76 (65.0–83.8)
Acute respiratory illness 87 (83.8–89.1) 36 (34.3–38.3) 33 (30.5–35.1) 89 (86.6–91.1)
Febrile acute respiratory illness (measured fever only) 69 (65.0–72.2) 53 (51.1–55.2) 34 (31.3–36.5) 83 (80.7–85.1)
Febrile acute respiratory illness (reported or measured fever) 86 (83.1–88.5) 37 (34.8–38.8) 33 (30.6–35.2) 89 (86.3–90.8)
Individual symptoms and symptom combinations
   Reported or measured fever 98 (96.3–98.7) 2 (1.0–2.1) 26 (24.0–27.5) 68 (52.0–79.9)
   Measured fever (> 38 °C) 80 (76.5–82.8) 21 (19.5–22.9) 26 (23.9–27.9) 74 (70.3–78.1)
   Cough 80 (77.1–83.3) 41 (39.3–43.4) 33 (30.7–35.5) 86 (83.9–88.4)
   Sore throat 58 (54.4–62.2) 64 (61.7–65.7) 37 (33.8–39.9) 82 (79.7–83.7)
   Shortness of breath 4 (2.6–5.9) 97 (96.0–97.6) 33 (23.0–44.5) 72 (70.1–74.1)
   Myalgia 73 (69.5–76.4) 27 (25.3–29.0) 26 (23.7–27.8) 74 (70.1–77.0)
   Headache 86 (83.1–88.5) 10 (9.0–11.6) 25 (23.6–27.4) 72 (66.4–76.4)
   Cough and reported or measured fever 80 (76.1–82.5) 42 (40.2–44.3) 33 (30.7–35.6) 86 (83.7–88.2)
   Sore throat and reported or measured fever 58 (54.0–61.8) 64 (62.1–66.1) 37 (33.8–39.9) 82 (79.7–83.7)
Influenza-like illness (measured fever) and either myalgia or headache 63 (59.0–66.7) 56 (53.9–58.6) 29 (26.9–32.0) 84 (82.1–85.7)
Influenza-like illness (reported or measured fever) and either myalgia or headache 77 (73.8–80.4) 45 (42.4–47.1) 22 (20.1–23.7) 78 (75.1–80.8)

a Calculated for the period when > 10% of the tested patients were found positive for an influenza virus (June 2009–October 2010).