OBJECTIVE: To evaluate the significance of serum specific antibodies against severe acute respiratory syndrome (SARS) virus in the diagnosis of SARS and the concordance of IFA and ELISA in the antibodies measurements. METHODS: Specific antibodies of IgM and IgG against SARS virus in 267 serum specimens from patients with SARS and 132 from non-SARS patients or healthy persons were assayed with IFA or ELISA. The sensitivity, specificity, positive predictive value (ppv), negative predictive value (NPV), and accuracy were used to evaluate the significance of the antibodies in diagnosis of SARS. The concordance of different measurements was tested with Kappa. RESULTS: The positive rate of specific IgM and IgG detected by IFA increased sharply on the eleventh day of the disease. The sensitivity, specificity, PPV, NPV, and accuracy of IgM in diagnosis of SARS on eleventh day or later were 65.6%, 100.0%, 100.0%, 71.0% and 81.3%, respectively, and IgG were 91.1%, 97.0% 97.3%, 90.1%, and 93.8%, respectively. Similar results could be seen when IgM and IgG were detected by ELISA. The Kappa of IFA and ELISA for IgM and IgG were 0.640 and 0.779 respectively. CONCLUSIONS: The antibodies against SARS virus can be detected in the mid-and late stage of SARS. The antibodies can be used in the serological diagnosis of SARS. There is high concordance of IFA and ELISA results in measurement of SARS antibodies.
OBJECTIVE: To evaluate the significance of serum specific antibodies against severe acute respiratory syndrome (SARS) virus in the diagnosis of SARS and the concordance of IFA and ELISA in the antibodies measurements. METHODS: Specific antibodies of IgM and IgG against SARS virus in 267 serum specimens from patients with SARS and 132 from non-SARSpatients or healthy persons were assayed with IFA or ELISA. The sensitivity, specificity, positive predictive value (ppv), negative predictive value (NPV), and accuracy were used to evaluate the significance of the antibodies in diagnosis of SARS. The concordance of different measurements was tested with Kappa. RESULTS: The positive rate of specific IgM and IgG detected by IFA increased sharply on the eleventh day of the disease. The sensitivity, specificity, PPV, NPV, and accuracy of IgM in diagnosis of SARS on eleventh day or later were 65.6%, 100.0%, 100.0%, 71.0% and 81.3%, respectively, and IgG were 91.1%, 97.0% 97.3%, 90.1%, and 93.8%, respectively. Similar results could be seen when IgM and IgG were detected by ELISA. The Kappa of IFA and ELISA for IgM and IgG were 0.640 and 0.779 respectively. CONCLUSIONS: The antibodies against SARS virus can be detected in the mid-and late stage of SARS. The antibodies can be used in the serological diagnosis of SARS. There is high concordance of IFA and ELISA results in measurement of SARS antibodies.