Abstract
The demand for sensitive and specific assays to determine immune status to varicella can be expected to increase with the anticipated availability of a varicella-zoster virus vaccine for use in nonimmune adults, especially health care personnel, and in immunosuppressed children. Although the fluorescent-antibody-to-membrane-antigen (FAMA) test remains the reference standard to which other tests are compared, simpler alternative assays are needed. In this study, the FAMA was compared with a simple indirect immunofluorescence assay (IFA) and a commercially available enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to varicella-zoster virus. One hundred and twelve serum samples were screened by the FAMA test and IFA at a 1:5 dilution, and 100% agreement was found. Of these samples, 101 were available for testing by ELISA, and identical results were obtained with 97 samples (96% agreement). When the samples were screened at a 1:2 dilution, 99 of 101 results agreed. In addition, 31 spinal fluid samples were tested by all three methods. When screening was at a 1:2 dilution, there was 96.8% agreement between the FAMA test and IFA. When the cutoff value established for sera was used for the spinal fluid samples, there was 90.3% agreement between the ELISA and the FAMA test. Thus, both IFA and ELISA can be considered sensitive and specific alternatives to the FAMA test, and in addition, both use commercially available reagents.