Table 2 Performance of BD rapid test compared with rRT-PCR test for nasal swabs in Kenya, July 2013–July 2014 (N = 3,199)
Characteristic | Specimens | %Sensitivity | %Specificity | %PPV | %NPV | |
|---|---|---|---|---|---|---|
n, | %positive | (CI, 95%) | (CI, 95%) | (CI, 95%) | (CI, 95%) | |
Influenza Type | ||||||
Influenza A or B | 321 | 10.0 | 77.0 (72.6–80.9) | 94.9 (94.0–95.7) | 69.5 (65.0–73.6) | 96.5 (95.7–97.1) |
Influenza A | 270 | 8.4 | 77.8 (73.0–82.0) | 95.8 (94.4–96.0) | 66.5 (61.7–71.0) | 97.2 (96.5–97.8) |
Influenza B | 46 | 1.4 | 63.9 (51.7–74.6) | 99.6 (99.3–99.8) | 79.3 (66.3–88.4) | 99.2 (98.9–99.4) |
Case Type: | ||||||
SARI (n = 2059) | 178 | 8.6 | 74.2 (68.1–79.5) | 94.9 (93.7–95.8) | 65.7 (59.7–71.3) | 96.5 (95.6–97.3) |
ILI (n = 1140) | 143 | 12.5 | 80.8 (73.4–82.4) | 95.0 (94.4–96.0) | 74.9 (61.5–70.9) | 96.4 (96.7–97.9) |
Department: | ||||||
Inpatienta (n = 1480) | 122 | 8.2 | 76.3 (69.3–82.8) | 95.2 (93.9–96.3) | 65.9 (58.9–72.7) | 97.1 (96.0–97.9) |
Outpatient (n = 498) | 80 | 16.1 | 87.0 (77.9–92.8) | 95.6 (93.0–97.3) | 81.6 (72.3–88.5) | 97.0 (94.7–98.4) |
Age: | ||||||
< 5 years (n = 2512) | 237 | 9.4 | 78.0 (72.8–82.4) | 95.1 (94.1–96.0) | 68.7 (63.5–73.5) | 96.9 (96.1–97.6) |
≥ 5 years (n = 687) | 84 | 12.2 | 74.3 (65.1–81.9) | 94.3 (91.9–96.0) | 71.8 (62.6–79.5) | 94.9 (92.7–96.5) |
Illness onset to sample collection: | ||||||
Less than 2 days (n = 346) | 23 | 6.6 | 65.7 (47.7–80.3) | 92.0 (88.2–94.6) | 47.9 (33.5–62.6) | 96.0 (92.9–97.8) |
≥ 2 to 3 days (n = 1267) | 145 | 11.4 | 79.2 (75.5–84.7) | 95.5 (94.0–96.6) | 74.7 (67.9–80.6) | 96.5 (95.1–97.4) |
> 3 to 4 days (n = 454) | 44 | 9.7 | 80.0 (66.7–89.1) | 94.5 (91.6–96.4) | 66.7 (53.9–77.5) | 97.2 (94.8–98.5) |
> 4 to 5 days (n = 337) | 30 | 8.9 | 75.0 (58.5–86.8) | 96.0 (92.9–97.8) | 71.4 (55.2–83.8) | 96.6 (93.7–98.3) |
> 5 to 6 days (n = 237) | 21 | 8.9 | 77.8 (57.3–90.6) | 95.2 (91.2–97.6) | 67.7 (48.5–82.7) | 97.1 (93.5–98.8) |
> 6 to 7 days (n = 174) | 18 | 10.3 | 69.2 (48.1–84.9) | 93.9 (88.4–97.0) | 66.7 (46.0–82.8) | 94.6 (89.2–97.4) |
> 7 days (n = 298) | 23 | 7.7 | 76.7 (57.3–89.4) | 95.9 (92.6–97.8) | 67.6 (49.4–82.0) | 97.3 (94.4–98.8) |
≤ 7 days (n = 2727) | 280 | 10.3 | 77.6 (72.8–81.7) | 94.9 (93.9–95.7) | 69.8 (65.0–74.2) | 96.5 (95.7–97.2) |
Sample collection to sample testingb: | ||||||
> 7 days (n = 2834) | 305 | 10.8 | 76.3 (71.9–80.4) | 95.2 (94.3–96.0) | 72.4 (67.9–76.6) | 96.1 (95.2–96.8) |
≤ 7 days (n = 365) | 16 | 4.4 | 94.1 (69.2–99.7) | 92.8 (89.4–95.2) | 39.0 (24.6–55.5) | 99.7 (98.0–100) |
Influenza Prevalence | ||||||
Influenza activity <5% (n = 640) | 13 | 2.0 | 72.2 (46.4–89.3) | 95.7 (93.7–97.1) | 32.5 (19.1–49.2) | 99.2 (98.0–99.7) |
Influenza activity 5to10% (n = 875) | 42 | 4.8 | 76.4 (62.7–86.3) | 95.0 (93.2–96.3) | 50.6 (39.5–61.7) | 98.4 (97.2–99.1) |
Influenza activity >10to15% (n = 354) | 28 | 7.9 | 71.8 (54.9–84.5) | 95.2 (92.1–97.2) | 65.1 (49.0–78.5) | 96.5 (93.6–98.1) |
Influenza activity >15% (n = 1334) | 238 | 17.9 | 78.1 (73.0–82.5) | 94.4 (92.7–95.7) | 80.5 (75.4–84.7) | 93.5 (91.8–94.9) |
Influenza activity ≥10%(n = 1684) | 266 | 15.8 | 77.3 (72.5–81.6) | 94.6 (93.2–95.7) | 78.5 (73.6–82.6) | 94.2 (92.8–95.4) |
Flu activity <10% (n = 1515) | 56 | 3.6 | 75.3 (63.6–84.4) | 95.3 (94.0–96.3) | 44.7 (35.8–53.9) | 98.7 (97.9–99.2) |
Surveillance Site: | ||||||
Kibera (n = 722) | 85 | 11.8 | 73.9 (64.7–81.5) | 95.6 (93.5–99.7) | 75.9 (66.7–83.3) | 95.1 (93.1–96.6) |
Lwak (n = 499) | 34 | 6.8 | 68.0 (53.2–80.1) | 92.7 (89.7–94.8) | 50.7 (38.4–63.0) | 96.3 (94.0–97.8) |
Mombasa (595) | 55 | 9.2 | 79.7 (68.0–88.1) | 95.1 (92.7–96.7) | 67.9 (56.5–77.6) | 97.3 (95.4–98.4) |
Nakuru(874) | 110 | 12.6 | 84.6 (77.0–90.1) | 94.0 (91.9–95.5) | 71.0 (63.0–77.8) | 97.2 (95.7–98.3) |
Nyeri (n = 509) | 37 | 7.3 | 69.8 (55.5–81.3) | 97.8 (95.9–98.9) | 78.7 (63.9–88.8) | 96.5 (94.3–97.9) |