Table 3 Performance of BD rapid test compared with rRT-PCR test for NP/OP swabs in Kenya, July 2013–June 2014 (N = 3,119)
Characteristic | Specimens | %Sensitivity | %Specificity | %PPV | %NPV | |
|---|---|---|---|---|---|---|
n | %positive | (CI, 95%) | (CI, 95%) | (CI, 95%) | (CI, 95%) | |
Influenza Type | ||||||
Influenza A or B | 295 | 9.5 | 67.4 (63.0–71.7) | 94.1 (93.2–95.0) | 65.3 (60.9–69.6) | 94.6 (93.8–95.5) |
Influenza A | 248 | 8.0 | 71.7 (66.9–76.4) | 94.7 (93.8–95.5) | 62.6 (57.9–67.4) | 96.4 (95.7–97.1) |
Influenza B | 41 | 1.3 | 43.2 (33.2–54.1) | 99.4 (99.2–99.7) | 70.7 (58.0–82.4) | 98.2 (97.8–98.7) |
Case Type: | ||||||
SARI (n = 1995) | 160 | 8.0 | 65.0 (58.7–70.9) | 94.1 (92.9–95.1) | 60.8 (54.6–66.7)) | 95.0 (93.9–96.0) |
ILI (n = 1124) | 135 | 12.0 | 70.3 (63.2–75.6) | 94.2 (92.5–95.6) | 71.4 (63.3–77.6) | 93.9 (92.1–95.3) |
Department: | ||||||
Inpatienta (n = 1,429) | 105 | 7.3 | 69.5 (61.4–76.6) | 94.1 (92.6–95.3) | 58.0 (50.4–65.2) | 96.3 (95.1–97.3) |
Outpatient (n = 489) | 77 | 15.7 | 80.2 (70.5–87.4) | 94.7 (91.8–96.6) | 78.6 (68.9–86.0) | 95.1 (92.4–97.0) |
Age: | ||||||
< 5 years (n = 2,443) | 217 | 8.9 | 70.5 (65.0–75.4) | 94.2 (93.1–95.1) | 63.7 (58.4–68.9) | 95.7 (94.9–96.6) |
≥ 5 years (n = 676) | 78 | 11.5 | 60.0 (51.0–68.4) | 93.8 (90.5–94.9) | 69.6 (57.3–74.9) | 90.8 (88.1–93.1) |
Duration of illness onset to sample collection: | ||||||
Less than 2 days (n = 341) | 23 | 6.7 | 54.8 (38.8–69.8) | 92.0 (88.1–94.7) | 48.9 (34.3–69.7) | 93.5 (90.0–96.0) |
≥ 2 to 3 days (n = 1245) | 133 | 10.7 | 68.2 (61.1–74.6) | 94.5 (92.9–96.7) | 69.6 (62.5–76.0) | 94.1 (92.5–95.4) |
> 3 to 4 days (n = 443) | 44 | 9.9 | 69.8 (56.8–80.4) | 94.2 (91.2–96.3) | 66.7 (53.9–77.5) | 95.0 (92.1–96.9) |
> 4 to 5 days (n = 326) | 25 | 7.7 | 73.5 (55.3–86.5) | 94.5 (91.1–96.7) | 61.0 (44.5–75.4) | 96.8 (93.9–98.5) |
> 5 to 6 days (n = 232) | 21 | 9.1 | 75.0 (54.8–88.6) | 95.1 (90.9–97.5) | 67.7 (48.5–82.7) | 96.5 (92.7–98.5) |
> 6 to 7 days (n = 170) | 16 | 9.4 | 59.3 (39.0–77.0) | 93.0 (86.7–96.0) | 61.5 (40.7–79.1) | 92.4 (86.7–96.0) |
> 7 days (n = 453) | 34 | 7.5 | 61.8 (47.7–74.3) | 93.7 (90.6–95.8) | 56.6 (44.1–70.2) | 94.7 (91.8–96.6) |
≤ 7 days (n = 2666) | 261 | 9.8 | 68.1 (63.2–72.7) | 94.2 (93.2–95.1) | 66.4 (61.5–71.0) | 94.6 (93.6–95.5) |
Time of sample collection to sample testing: | ||||||
> 7 days (n = 2,773) | 281 | 10.1 | 67.7 (62.9–72.1) | 94.4 (93.3–95.2) | 67.9 (63.1–72.3) | 94.3 (93.3–95.2) |
< 7 days (n = 346) | 14 | 4.0 | 60.9 (38.8–79.5) | 92.6 (89.0–95.1) | 36.8 (22.3–54.0) | 97.1 (94.4–98.6) |
Influenza Prevalence | ||||||
Flu activity <5% (n = 619) | 11 | 1.8 | 91.7 (59.8–99.6) | 95.6 (93.5–97.0) | 28.9 (16.0–46.1) | 99.8 (98.9–100) |
Flu activity ≥ 5to < 10%(n = 857) | 33 | 3.9 | 53.2 (40.2–65.8) | 94.1 (92.3–95.6) | 41.3 (30.5–52.8) | 96.3 (94.6–97.4) |
Flu activity >10–15% (n = 342) | 28 | 8.2 | 70.0 (53.3–82.9) | 95.0 (91.8–97.1) | 65.1 (49.0–78.5) | 96.0 (92.9–97.8) |
Flu activity >15% (n = 1301) | 223 | 17.1 | 68.8 (63.4–73.8) | 93.0 (91.2–94.5) | 76.6 (71.3–81.3) | 90.0 (87.9–91.7) |
Flu activity ≥10% (n = 1,643) | 251 | 15.3 | 69.0 (63.9–75.6) | 93.5 (92.0–94.8) | 75.1 (70.1–79.6) | 91.4 (89.7–92.8) |
Flu activity <10% (1,476) | 44 | 3.0 | 59.5 (47.4–70.5) | 94.7 (93.4–95.8) | 37.3 (28.7–46.7) | 97.8 (96.9–98.5) |
Site: | ||||||
Kibera (n = 707) | 79 | 11.2 | 60.3 (51.4–68.6) | 95.3 (93.2–96.8) | 74.5 (65.0–82.3) | 91.3 (88.7–93.4) |
Lwak (494) | 34 | 6.9 | 56.7 (43.3–69.2) | 92.4 (89.5–94.7) | 50.7 (38.4–63.0) | 93.9 (91.1–95.9) |
Mombasa(n = 562) | 45 | 7.9 | 72.6 (59.6–82.8) | 93.3 (90.6–95.2) | 57.0 (45.4–67.9) | 96.5 (94.4–97.9) |
Nakuru (n = 851) | 102 | 12.0 | 77.9 (69.6–84.4) | 92.9 (90.7–94.6) | 66.7 (58.5–73.9) | 95.8 (94.0–97.2) |
Nyeri (n = 500) | 35 | 7.0 | 64.1 (50.6–77.8) | 97.3 (95.2–98.5) | 74.5 (59.4–84.9) | 95.8 (93.4–97.4) |