Indium-111 labelled platelet scintigraphy can predict the immunological origin of fever in patients on dialysis carrying a non-functioning renal allograft

The purpose of this study was to evaluate the usefulness of labelled platel et scintigraphy in the differential diagnosis of a prolonged febrile syndro me (PFS) in patients on dialysis carrying a non-functioning renal allograft . We prospectively performed an indium-lll mercaptopyridine-labelled platel et scan on 91 patients (54 men, 37 women; mean age 39.6+/-12 years). The me an duration of PFS was 35 days (range 7-122). Forty six of the 91 patients underwent steroid therapy (2-10 mg/day). Platelet labelling was carried out following Thakur's method. Platelet scans were performed 48 h after reinje ction of labelled platelets. The platelet uptake index (PUI) was calculated by dividing the cpm/pixel in the allograft ROI by cpm/pixel in a mirror ba ckground ROI. The final diagnosis of PFS was established depending on the o utcome after treatment. In 61/91 patients the fever had an immunological or igin because it disappeared after graft embolisation or transplantectomy. I n 30/91 patients the PFS disappeared after antibiotic therapy (non-immunolo gical origin). The PUI in patients with immunological PFS was 1.80+/-0.7, w hile in patients with non-immunological PFS it was 1.12+/-0.1 (P<0.05). Whe n a PUI of greater than or equal to 1.5 was considered as the threshold to establish PFS of immunological origin, the sensitivity of platelet scan was 76%, the specificity 100%, and the negative and positive predictive values 69% and 100%, respectively. In patients classified with immunological PFS who underwent steroid therapy, the PUI was significantly lower than in pati ents without steroids (P<0.05), These results suggest that In-111-labelled platelet scintigraphy can accurately predict an immunological PFS in patien ts on dialysis carrying a non-functioning renal allograft, Therapy with ste roids could reduce the sensitivity of In-111-labelled platelet scintigraphy in detecting immunological PFS.