Utility of 111In-labelled leucocyte scintigraphy in patients with fever of unknown origin in an era of changing disease spectrum and investigational techniques.

BACKGROUND

(111)In-labelled leucocyte, imaging is often used to investigate patients with fever of unknown origin (FUO). Its diagnostic performance, however, has been variable and a broad range of sensitivities and specificities have been reported. The purpose of this investigation was to evaluate the usefulness of (111)In-labelled leucocytes scintigraphy in the detection of a cause of FUO in the light of a changing spectrum of diseases causing it and advances in investigational techniques.

MATERIALS AND METHODS

Sixty-one patients with a clinical diagnosis of FUO underwent whole-body (111)In-troponolate-labelled leucocyte scintigraphy in our department over a 2-year period between February 2004 and February 2006. Of these, 54 patients were retrospectively reviewed to identify a cause of FUO. Other parameters such as C-reactive protein (CRP), leucocyte count and radiological findings were also evaluated.

RESULTS

Leucocyte scintigraphy was found to be true positive in 12 patients, true negative in 24 patients, false positive in 10 patients and false negative in eight patients. The overall sensitivity of scintigraphy was 60%, specificity 71%, positive predictive value 55%, and negative predictive value 75%. There was no difference in the scintigraphic sensitivity between patients with spontaneous FUO and those with post-operative FUO although the latter showed a higher specificity and PPV. CRP and leucocyte count did not differ significantly between patients with true positive and true negative scintigrams. Overall, 83% of patients with abnormal radiological examinations had positive findings on scintigraphy and 87% of patients with negative findings on radiology had normal scintigraphy.

CONCLUSION

Despite changes in disease spectrum and advances in investigational techniques, our results suggest that (111)In-leucocyte scintigraphy is still a useful technique in establishing the cause of FUO. A higher PPV of this test in post-operative situations makes it especially applicable in this category of patients. Equally, the higher NPV in patients with spontaneous FUO virtually excludes infection/inflammation. Finally, a higher pre-test probability based on the radiological tests seems to be important in the optimal use of leucocyte imaging.