Table 3.

Results obtained for shell vial, standard cell culture, ELISA, Directigen Flu A and QCM methods in comparison with RT-PCR.

Test	No of specimens					Sensitivitye	Specificityf	PPVg	NPVh
	TPa	TNb	FPc	FNd
Shell vial	Influenza A	28	27	3	9	76	90	90	75
	Influenza B	12	52	0	3	80	100	100	95
Cell culture	Influenza A	30	30	0	7	81	100	100	81
	Influenza B	15	52	0	0	100	100	100	100
ELISA	Influenza A	25	30	0	12	68	100	100	71
	Influenza B	9	52	0	6	60	100	100	90
Directigen Flu A	Influenza A	13	30	0	24	35	100	100	56
	Influenza B	NA	NA	NA	NA	NA	NA	NA	NA
QCM	Influenza A	28	30	0	9	76	100	100	77
	Influenza B	12	52	0	3	80	100	100	95
QCM (nanoparticles)	Influenza A	30	30	0	7	81	100	100	95
	Influenza B	13	52	0	2	87	100	100	96

A total of 67 nasal samples were compared with RT-PCR which was used as the reference method (gold standard).

Samples positive by shell vial, standard cell culture, ELISA, Directigen Flu A kit and QCM, but negative by RT-PCR, were considered FP. Samples that were identified by RT-PCR assays were considered as TP. Samples that were negative by shell vial, standard cell culture, ELISA, BD Directigen Flu A kit and QCM but positive by PCR were regarded as FN. A sample that was negative by RT-PCR was a TN.

^aTP, true-positives.

^bTN, true-negatives.

^cFP, false-positives.

^dFN, false-negatives.

^eSensitivity = number of TP specimens/(number of TP + number of FN specimens) × 100.

^fSpecificity = number of TN specimens/(number of TN specimens + number of FP specimens) × 100.

^gPPV (positive predictive value) = TP/(TP + FP) × 100.

^hNPV (negative predictive value) = TN/(TN + TN) × 100.