TABLE 3.

Performance characteristics of the various assaysa

AssayInfluenza A virusswH1
% Sn% Sp% PPV% NPV% Sn% Sp% PPV% NPV
Duplex RT-PCR (55°C)b97.2 (93.8-97.2)100 (98.1-100)100 (96.5-100)98.4 (93.1-98.4)93.9 (90.0-93.9)100 (98.0-100)100 (95.8-100)97.1 (95.1-97.1)
Duplex RT-PCR (50°C)b97.2 (93.8-97.2)100 (98.1-100)100 (96.5-100)98.4 (93.1-98.4)77.3 (72.6-77.3)100 (97.7-100)100 (94.0-100)89.8 (87.7-89.8)
Monoplex RT-PCRc74.6 (70.3-74.6)100 (97.6-100)100 (94.1-100)87.6 (85.4-87.6)80.3 (75.7-80.3)100 (97.7-100)100 (94.3-100)91.0 (89.0-91.0)
Real-time RT-PCRc71.8 (67.4-71.8)100 (97.5-100)100 (93.9-100)86.4 (84.3-86.4)90.9 (86.7-90.9)100 (97.9-100)100 (95.4-100)95.7 (93.6-100)
Triplex RT-PCR47.9 (43.4-47.9)100 (97.5-100)100 (90.6-100)77.4 (75.5-77.4)
Rapid antigen testing12.7 (9.0-12.7)100 (97.9-100)100 (71.0-100)67.2 (65.8-67.2)
  • a The sensitivities (Sn), specificities (Sp), positive predictive values (PPV), and negative predictive values (NPV) were calculated by comparison to the results obtained with a modified gold standard (see Materials and Methods); 95% confidence intervals are indicated in parentheses. The results for influenza A virus are based on 71 confirmed cases (66 cases of pandemic [H1N1] 2009 influenza virus infection, 3 cases of seasonal [H1N1] influenza A virus infection, and 2 cases of seasonal [H3N2] influenza virus infection). The results for swH1 were calculated on the basis of the data for the 66 confirmed cases of pandemic (H1N1) 2009 influenza virus infection. A P value of <0.05 was considered statistically significant.

  • b The duplex RT-assay PCR was evaluated by using annealing temperatures of 50°C and 55°C.

  • c For the monoplex and real-time RT-PCRs, the detection of influenza A virus and swH1 was performed in independent reactions.