title: Evaluation and validation of an enzyme-linked immunosorbent assay and an immunochromatographic test for serological diagnosis of severe acute respiratory syndrome.
abstract: 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.
authors.affiliation: Genelabs Diagnostics Pte Ltd., Singapore, Republic of Singapore. guanming@mail.genelabs.com.sg
authors.forename: Ming
authors.initials: M
authors.lastname: Guan
authors.forename: Kwok Hung
authors.initials: KH
authors.lastname: Chan
authors.forename: J S Malik
authors.initials: JS
authors.lastname: Peiris
authors.forename: See Wai
authors.initials: SW
authors.lastname: Kwan
authors.forename: Siu Yan
authors.initials: SY
authors.lastname: Lam
authors.forename: Chiu Mei
authors.initials: CM
authors.lastname: Pang
authors.forename: Ka Wing
authors.initials: KW
authors.lastname: Chu
authors.forename: Kit Man
authors.initials: KM
authors.lastname: Chan
authors.forename: Hsiao Ying
authors.initials: HY
authors.lastname: Chen
authors.forename: Ewe Beng
authors.initials: EB
authors.lastname: Phuah
authors.forename: Caiqin Jane
authors.initials: CJ
authors.lastname: Wong
mesh_terms: 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
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D011994:Recombinant Proteins