Prospective analysis of 18-F-FDG positron emission tomography (PET) and 111-In leucocyte scintigraphy (LS) in the management of fever of unknown origin (FUO)

Objectives The aim of this study is to compare the diagnostic performance of 18F-FDG-PET (PET) and 111In-labelled leucocyte scintigraphy (LS) in the management of fever of unknown origin (FUO).

Methods Twenty-one consecutive patients with FUO were prospectively studied using whole-body LS and PET within a week of each other. Performance of the two modalities for identifying the aetiology of FUO was evaluated. Final diagnosis was based on biopsy, microbiological tests and imaging follow-up.

Results Abnormal tracer uptake was seen on LS in 3/21 (14%) patients and on PET in 8/21 (38%) patients, suggesting a higher sensitivity for PET (McNemar’s test, p<0.01). All LS positive cases were identified on PET and confirmed as infection. The causes of FUO on PET in others were: benign (n=2), infection (n=2) and vasculitis (n=1). Of 13 patients with normal investigations, 10 made spontaneous recovery during the follow-up period and no definite cause for FUO was found following further investigations. One patient was diagnosed with Still’s disease, one polymyalgia rheumatica and another died of menigoencephalitis.

Conclusions PET has a higher sensitivity than LS in the assessment of FUO. PET, where available, may be used as the non-invasive diagnostic modality of choice in the assessment of FUO

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Contingency Tables of LS and PET

Two contingency tables with number of cases (LS on the left, PET on the right). LS shows sensitivity 30%, specificity 100%. PET shows sensitivity 60%, specificity 82%.