Diagnostic value of (111)In-granulocyte scintigraphy in patients with fever of unknown origin.

UNLABELLED 111In-granulocyte scintigraphy is often used as a diagnostic tool in patients with fever of unknown origin (FUO). However, its diagnostic performance has been studied in only a limited number of investigations, with most having been published more than 10 y ago; in addition, a broad range of sensitivities and specificities has been reported. Therefore, the aim of this study was to investigate the diagnostic value of granulocyte scintigraphy in patients fulfilling the criteria of FUO. Also studied was whether increased peripheral leukocyte count or C-reactive protein (CRP) level could be used to select patients for scintigraphy to raise the diagnostic value. METHODS For 31 patients with true FUO who underwent granulocyte scintigraphy at a third-line referral hospital between 1995 and 2000, the files and scintigraphy findings were reviewed retrospectively to test the ability of scintigraphy to identify infection or chronic inflammatory bowel disease as the cause of FUO. In addition, leukocyte counts and CRP values were recorded. RESULTS Scintigrams were true-positive in 6 cases, false-positive in 4 cases, true-negative in 19 cases, and false-negative in 2 cases. Sensitivity was 75%, specificity was 83%, the predictive value of a scintigram showing positive findings was 60%, and the predictive value of a scintigram showing negative findings was 90%. Leukocyte counts did not differ between patients with true-positive and true-negative scintigrams. In contrast, CRP was elevated in all patients with true-positive scintigrams but in only half the patients with true-negative scintigrams. However, if only patients with elevated CRP were used for calculation of test performance, the test performance was not improved. CONCLUSION (111)In-granulocyte scintigraphy seems to have a reasonable sensitivity and specificity in cases of FUO, when one takes into account that (111)In-granulocyte scintigraphy is not a first-line test. The high predictive value of a scintigram showing negative findings may be especially valuable for ruling out an infectious cause of FUO. Neither peripheral leukocyte count nor CRP levels seem useful for selection of patients on whom scintigraphy should be performed.