Table 2. Diagnostic performance of NS1 rapid test in enrolment plasma samples and odds of NS1 detection in relation to plasma viremia.
| Laboratory-confirmed dengue cases | Non-dengue cases | Total | ||
|---|---|---|---|---|
| NS1 rapid test positive | 1192 | 32 | 1224 | PPV % = 97.4% (96.3–98.2%) |
| NS1 rapid test negative | 500 | 3983 | 4483 | NPV % = 88.9% (87.9–89.8%) |
| Total | 1692 | 4015 | 5707 | |
| Median (IQR) plasma viral RNA concentration (log10copies/ml) a | OR (95%CI) | Sensitivity % (95%CI) | Specificity % (95%CI) | |
| All serotypes (n = 1692) | 7.3 (6.2–8.3) | 1.8 (1.6–1.9) | 70.4% (68.2–72.6%) | 99.2% (98.9–99.5%) |
| DENV-1 (n = 629) | 7.9 (6.6–8.7) | 2.0 (1.8–2.3) | 80.3 (77.0–83.3%) | - |
| DENV-2 (n = 399) | 7.0 (6.0–7.9) | 1.8 (1.5–2.1) | 46.4 (41.4–51.4%) | - |
| DENV-3 (n = 154) | 7.5 (6.4–8.6) | 1.4 (1.1–1.9) | 85.1 (78.4–90.3%) | - |
| DENV-4 (n = 433) | 6.9 (6.0–7.7) | 1.5 (1.3–1.8) | 75.8 (71.3–79.7%) | - |
a Viremia measurement in the enrolment plasma sample (the same sample was also used for NS1 testing).
PPV: positive predictive value; NPV: negative predictive value; DENV: dengue virus; OR: odds ratios for detecting NS1 for each 10-fold higher DENV RNA concentration. There were 77 dengue cases where the infecting serotype was unknown.