Diagnostic sensitivity and specificity of the radionuclide (indium)-labeled leukocyte scan

SummaryObjectiveEvaluate the sensitivity and specificity of Indium111-labeled leukocyte scans as used in a general, tertiary care hospital.MethodsRetrospective review of electronic medical records from all patients who underwent Indium111 scan at two large Veterans Affairs Medical Centers, 1999–2005, to determine congruence between Indium111 scan readings and final clinical diagnoses, using all available data with at least 6 months of follow-up.ResultsOf 145 indium scans done for possible skeletal infection, infection was judged to be present in 52 cases. The sensitivity was 83%, and the specificity was 90%, with a diagnostic accuracy of 88%. Fifty-nine scans were done for indications other than skeletal infection. In 20 instances, when specific foci were suspected, the suspicion was correctly confirmed by indium scan in every case, without false positives or negatives (sensitivity and specificity, 100%). In 39 scans done to search for a possible source of nonspecific findings of infection (fever, leukocytosis, bacteremia), the sensitivity and specificity were 81% and 87%, respectively, with a diagnostic accuracy of 85%.ConclusionExcept as a means to confirm an already-suspected clinical focus, the indium scan appears to offer relatively little definitive information that can be used for diagnosis or treatment of infection.