Evaluation and validation of an enzyme-linked immunosorbent assay and an immunochromatographic test for serological diagnosis of severe acute respiratory syndrome.
A newly developed severe acute respiratory syndrome (SARS)-specific enzyme-linked immunosorbent assay (ELISA) was further validated to confirm cutoff values and evaluate its diagnostic performance with clinical samples. In parallel, an immunochromatographic test was also evaluated. A total of 227 clinical serum specimens collected from SARS patients were used in the study, together with 385 samples from healthy donors. By use of an immunofluorescent (IF) test as the "gold standard", both the ELISA and the immunochromatographic test were able to detect immunoglobulin G antibodies to SARS not only from late-convalescent-stage samples (>21 days from the onset of clinical symptoms), as previously established, but also from early-acute-phase samples (1 to 10 days from onset). The ELISA, using an optical density (OD) of 0.25 as its cutoff value, produced the best sensitivity while maintaining high specificity. It detected SARS-specific antibodies in 58, 70, 75, and 95%, respectively, of the four groups of samples collected from patients 1 to 10 days, 11 to 20 days, 21 to 30 days, and more than 30 days after the onset of clinical symptoms. Similarly, the immunochromatographic test detected SARS-specific antibodies in 55, 68, 81, and 79% of the four groups, respectively. The overall specificities for the ELISA and the rapid test were 99.5 and 97.7%, respectively. Although the positive correlation observed between the ELISA OD values and the IF titers was moderate (r = 0.6915; P < 0.001), the detection rates of both the ELISA and the rapid test were found well in agreement with the IF titers.
Guan
Ming
M
Genelabs Diagnostics Pte Ltd., Singapore, Republic of Singapore. guanming@mail.genelabs.com.sg
Chan
Kwok Hung
KH
Peiris
J S Malik
JS
Kwan
See Wai
SW
Lam
Siu Yan
SY
Pang
Chiu Mei
CM
Chu
Ka Wing
KW
Chan
Kit Man
KM
Chen
Hsiao Ying
HY
Phuah
Ewe Beng
EB
Wong
Caiqin Jane
CJ
D000914:Antibodies, Viral / Q000097:blood; D002845:Chromatography / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D011994:Recombinant Proteins / Q000276:immunology; D012015:Reference Standards; D045473:Severe acute respiratory syndrome-related coronavirus / Q000276:immunology; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000592:standards*; D045169:Severe Acute Respiratory Syndrome / Q000097:blood / Q000175:diagnosis*; D013997:Time Factors
D000914:Antibodies, Viral; D007074:Immunoglobulin G; D011994:Recombinant Proteins