Volume 16, Number 5—May 2010
Dispatch
Rapid Influenza Antigen Test for Diagnosis of Pandemic (H1N1) 2009
Janice K. Louie
, Hugo Guevara, Erica Boston, Melissa Dahlke, Maria Nevarez, Tong Kong, Robert Schechter, Carol A. Glaser, and David P. Schnurr
, Hugo Guevara, Erica Boston, Melissa Dahlke, Maria Nevarez, Tong Kong, Robert Schechter, Carol A. Glaser, and David P. Schnurr
Table
Performance of rapid antigen test compared with PCR in the diagnosis of pandemic (H1N1) 2009*
| Parameter | All specimens | Patient age <18 y† | Patient age >18 y† |
|---|---|---|---|
| No. rapid test positive, PCR positive | 266 | 131 | 130 |
| No. rapid test positive, PCR negative | 49 | 19 | 28 |
| No. rapid test negative, PCR positive | 138 | 62 | 74 |
| No. rapid test negative, PCR negative | 250 | 78 | 166 |
| Total no. tested |
703 |
290 |
398 |
| Prevalence of PCR positives in sample | 0.57 | 0.67 | 0.51 |
| Sensitivity | 0.66 | 0.68 | 0.64 |
| Specificity | 0.84 | 0.80 | 0.86 |
| Positive predictive value | 0.84 | 0.87 | 0.82 |
| Negative predictive value |
0.64 |
0.56 |
0.69 |
| Positive likelihood ratio (95% CI) | 4.0 (3.1–5.2) | 3.5 (2.3–5.3) | 4.4 (3.1–6.3) |
| Posterior probability of positive test result (95% CI) | 0.84 (0.81–0.88) | 0.87 (0.82–0.91) | 0.82 (0.76–0.87) |
| Negative likelihood ratio (95% CI) | 0.41 (0.35–0.47) | 0.40 (0.32–0.50) | 0.42 (0.35–0.51) |
| Posterior probability of negative test result (95% CI) | 0.36 (0.32–0.39) | 0.44 (0.39–0.50) | 0.31 (0.27–0.35) |
*CI, confidence interval.
†Does not include results for 15 case-patients where age was not recorded.
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