Facilitating the laboratory diagnosis of infectious mononucleosis.

Sera from 501 patients with suspected infectious mononucleosis were tested by the sheep cell screening test (SCST) and the Monospot (Ortho) test; those with any positive results were examined by the full Paul-Bunnell titration. All sera in which the SCST and Monospot tests were both positive also gave a positive result with the full Paul-Bunnell titration. This indicated that the Monospot could be used as a confirmatory test for all sera giving a positive SCST, agreement between these two tests being considered diagnostic of infectious mononucleosis; the titration would be required only when the Monospot did not give a supporting positive result. Implementation of the above procedure, estimated to eliminate 86% of Paul-Bunnell titrations, has considerably reduced tedious laboratory work and enabled most positive diagnostic reports to be sent out 24 hr. earlier than before.