Monospot and VP1 tests in chronic fatigue syndrome and major depression.

Thirty-four patients with chronic fatigue syndrome (CFS) were compared with controls with DSM-III-R major depression on the Monospot and VP1 antigen tests. There was no significant difference in the numbers initially VP1 positive in the groups (11/34 and 7/34 positive in the chronic fatigue and major depression group respectively). Four CFS but no depressed patients were Monospot positive initially. No patient was both Monospot and VP1 positive. Patients positive on the tests were offered a repeat 6 months later. Eight of the 11 VP1 positive patients in the CFS group were retested and four remained positive, but none of the four depressed patients retested remained positive. No patient retested remained Monospot positive. The Monospot and VP1 tests appear to have little discriminating ability between these groups as screening tests and their predictive validity is unclear.