Indium labelled leucocyte scintigraphy in occult infection: a comparison with ultrasound and computed tomography.

A review of five year's experience of the use of 111Indium labelled leucocyte scintigraphy (111In WBC) in the investigation of suspected sepsis is presented. The results of 257 111In WBC scans for which a definitive diagnosis was subsequently established were available for analysis. The findings are compared with those of ultrasound (130 cases) and computed tomography (82 cases) and the final clinical outcome. The sensitivity and specificity of the 111In WBC for the series were 97% and 91% respectively. The major cause of the false positive 111In WBC results was activity within the bowel not due to infection. Thrombus within the inferior vena cava caused a false positive 111In WBC result: this is previously undescribed. There were a large number of incorrect ultrasound results, particularly with abdominal and pelvic abscesses, pyelonephritis, peritonitis and non-infected fluid collections, showing that a negative ultrasound cannot exclude infection. The relative merits of the three modalities are discussed, emphasizing that more than one technique may be required to establish a diagnosis.