Table 2.
Comparison of individual influenza A virus-positive results to results when influenza A virus-positive specimens were pooled with negative specimensa
| Specimen |
CT value forb: |
|||
|---|---|---|---|---|
| InfA | swInfA | swH1 | RP | |
| CS1 | 20 ± 1 | 21 ± 2 | 25 ± 1 | 25 ± 1 |
| Spiked pools | 20 ± 1 | 21 ± 2 | 24 ± 1 | 22 ± 1 |
| CS2 | 20 ± 1 | 20 ± 3 | 24 ± 1 | 24 ± 1 |
| Spiked pools | 20 ± 1 | 21 ± 2 | 24 ± 1 | 22 ± 2 |
| CS3 | 26 ± 1 | 26 ± 1 | 29 ± 0 | 26 ± 1 |
| Spiked pools | 26 ± 1 | 26 ± 2 | 28 ± 1 | 24 ± 2 |
Nine negative clinical specimens and one specimen positive for the 2009 H1N1 virus were combined to create pools of 10 clinical specimens. Three unique clinical specimens (CS1, CS2, and CS3) positive for the 2009 H1N1 virus were each spiked into five pools of negative specimens. The positive specimens were diluted in VTM for use as controls. The crossing threshold values of CS1, CS2, and CS3 diluted in VTM were compared to the PCR results of pools containing the corresponding positive specimens (spiked pools). Each pool and specimen in VTM was extracted once, and PCR was performed in triplicates. The values are the means ± standard deviations of the triplicates.
InfA, influenza A virus matrix (M) gene target for detecting any influenza A virus; swInfA, influenza A virus nucleoprotein (NP) gene from swine for detecting swine influenza virus in the genetic lineage of 2009 pandemic influenza A (H1N1); swH1, highly conserved region of hemagglutinin (HA) gene for detecting the 2009 pandemic influenza A virus (H1N1), subtype H1; RP, human ribonucleoprotein (RP) for detecting human RNase P RNA, used with human clinical specimens to indicate that adequate isolation of nucleic acid resulted from extraction of the clinical specimen.