Increased mean platelet volume in septicaemia.

An increased mean platelet volume (MPV), measured by the Coulter counter model S plus, was found in 13 of 25 patients with proven septicaemia but in none of 25 patients with localised bacterial infection and negative blood cultures. The increase in MPV was found both in patients with normal and low platelet counts and was not related to a particular micro-organism. Patients who responded favourably to antibiotic treatment all had normal MPVs after one week of treatment. However, 9 of 11 patients with a prolonged course of their infection due to endocarditis or abdominal abscesses had raised MPVs after seven days of treatment, and four patients who died of infection in the first week all had increased MPVs on the day of their death. An increased MPV in a patient with bacterial infection possibly indicates that the infection has become invasive--that is, that septicaemia has occurred. A persistent rise or further increase indicates that treatment is inadequate.