Flocked nasal swab versus nasopharyngeal aspirate for detection of respiratory tract viruses in immunocompromised adults: a matched comparative study

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.	Sensitivity^afor fNS (%)	Mean difference^bin Ct values (range)	Agreement^cbetween 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.

ISSN: 1471-2334