Interpretation

Positive antibody test results indicate previous infection with SARSCoV. Seroconversion from negative to positive or a four-fold rise in the antibody titer from acute to convalescent serum indicates a recent infection. A negative antibody test result later than 21 days after the onset of illness is likely to indicate that no infection with SARS-CoV has taken place. There seems to be no background seroprevalence against SARS-CoV in the control populations screened so far. Antibody testing allows the indirect diagnosis of SARS-CoV infection and is unsuitable during the acute illness; it has the advantage of being rather independent of the sample type and timing, in contrast to other virus detection methods.