Table 2.

Comparison of 53 diagnoses of suspected or probable cases of SARS by different assays

Test	Positive resultsa		Negative results	Total
	>10 copies per test	<10 copies per test
SARS-CoV gene chip
No. of results	9	9	35	53
Seroconversionb	6	5	0	11
Real-time nested PCRc
No. of results	10	8	35	53
Seroconversionb	7	4	0	11
Single-round RT-PCRd
No. of results	10	5	38	53
Seroconversionb	7	1	3	11
Shared results
No. of results	9e	5	35	49
Seroconversionb	6	1	0	7

^aResults of four independent tests.

^bData are number of samples obtained from patients for whom seroconversion was also noted, by ELISA and neutralizing antibody responses for available serum samples obtained during the convalescent phase of illness (ie, >28 days after onset of illness).

^cResults obtained by real-time nested PCR.¹⁷

^dResults obtained by hybridization probe-based detection using the RealArt HPA-coronavirus RT-PCR kit (Artus).

^eA total of nine samples were detected in the ‘>10 copies per test' with the gene chip method, and 10 samples with both nested and single-round PCR methods, because the virus copy number in case 18 was underestimated (see Table 3).