The significance of combining World Health Organization and Center for Disease Control criteria to resolve indeterminate human immunodeficiency virus type-1 Western blot results.

A total of 466 repeatedly reactive HIV-1 blood samples evidenced by enzyme immunoassay were analyzed by the Western blot method and interpreted according to WHO and CDC criteria. Discordant and indeterminate samples were further analyzed by PCR. When the Western blot result was classified as indeterminate, according to both WHO and CDC criteria, the PCR test was always negative. These findings suggest that samples with double-indeterminate status should be reported as negative.