THE VALUE OF INDIUM-111-LABELED LEUKOCYTE IMAGING AND ULTRASONOGRAPHYIN THE INVESTIGATION OF PYREXIA OF UNKNOWN ORIGIN

The aim of this study was to assess indium-lll leucocyte imaging and u ltrasound in the investigation of pyrexia of unknown origin (PUO), as well as the predictive value of available clinical information on the radiological outcome. 256 In-111 leucocyte scans performed over a 5 ye ar period were reviewed. There were 59 scans in 58 patients who fulfil led recognized criteria for true PUO; 47 of these patients had ultraso und. In 15 patients the fever settled and no diagnosis was made: the s ource of PUO was infective in 20 and non-infective in 24. In the group as a whole, the sensitivities of leucocyte scan and ultrasound were 2 5% and 23% with specificities of 100% and 83%, respectively. In infect ive cases of PUO, the sensitivities were 20% for both modalities. Ther e was no correlation between leucocyte count or differential, C reacti ve protein or the presence or absence of antibiotics. In the cases whe re the leucocyte scan led to the diagnosis of infection, the scan was performed within 4 weeks of the onset of symptoms. The results show th at an infective cause for PUO is established in less than 50% of cases . The leucocyte scan is specific and although not very sensitive can o ften be a guide to subsequent cross-sectional imaging. If an infective cause for the PUO is strongly suspected, In-111 leucocyte scanning ma y be more sensitive if performed in the first few weeks of fever.