Table 1

Detection of viruses in NPA and fNS specimens compared with total viral findings by either method

Virus

No. of samples in which virus was detected by:

Total no.

Sensitivitya for fNS (%)

Mean differenceb in Ct values (range)

Agreementc between NPA and fNS (95% CI d)


Both methods

NPA only

fNS only


Rhinovirus

7

2

0

9

78

3.2 (-2.0-6.5)

0.86 (0.68-1.05)

RSV A

1

1

1

3

5.8

RSV B

2

0

0

2

2.2 (5.6-9.9)

Influenza A

0

1

0

1

N/A

Influenza B

1

1

0

2

15.5

Bocavirus

0

1

0

1

N/A

Enterovirus

0

1

0

1

N/A

Metapneumovirus

0

0

1

1

N/A

Any virus

11

7

2

20

65

5.1 (-2.0-15.5)

0.66 (0.44-0.87)


NOTE. NPA, nasopharyngeal aspirate; fNS, flocked nasal swab; Ct, cycle of threshold; CI, confidence interval.

a Percentage of positive samples from fNS in relation to the total number of pairs with positive results from any of specimens.

b The Ct value for the flocked nasal swab minus the corresponding Ct value for NPA.

c Cohen's kappa: >0.8, almost perfect agreement; 0.6-0.8, substantial agreement; 0.4-0.6, moderate agreement; <0.4, poor agreement.

d CI, confidence interval.

Öhrmalm et al. BMC Infectious Diseases 2010 10:340   doi:10.1186/1471-2334-10-340

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