Comparative study of five methods for intratypic differentiation of polioviruses

A coded panel of 90 poliovirus isolates, 30 of each of the three known serotypes, was used to evaluate five methods for the intratypic differentiation of polioviruses: (i) an enzyme-linked immunosorbent assay with polyclonal cross-absorbed antisera (PAb-E), (ii) a neutralization assay with type-specific monoclonal antibodies (MAb-N), (iii) a restriction fragment length polymorphism (RFLP) assay, (iv) a Sabin vaccine strain-specific PCR assay, and (v) a Sabin vaccine strain-specific cRNA probe hybridization (ProHyb) assay. Sequence analysis was used for the definitive characterization of the strains. The panel was distributed to five laboratories; each laboratory analyzed the strains by at least two methods. Each method was used by three or four laboratories. The total performance scores (percentage correct results per number of tests) of the five methods were 96.7% for PAb-E, 93.9% for MAb-N, 91.9% for RFLP assay, 93.3% for Sabin vaccine strain-specific PCR, and 97.4% for Sabin vaccine strain-specific ProHyb. Consistent results were obtained by each laboratory for 88 of 90 isolates (97.8%) examined by PAb-E, 81 of 90 isolates (90.0%) examined by MAb-N, 78 of 90 isolates (86.7%) examined by RFLP assay, 81 of 90 isolates (90.0%) examined by PCR, and 89 of 90 isolates (98.9%) examined by ProHyb assay. Six strains were classified differently by different methods. It is recommended that at least two methods be used for the intratypic differentiation of poliovirus isolates, and each method should be based on a different principle (i.e., antigenic properties and nucleotide sequence composition). If two assays yield discrepant results, further characterization, preferably by partial sequence determination, will be required for correct identification.