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April 20, 2022

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Labeled White Blood Cell Scintigraphy Has Low Clinical Utility in Evaluation of Patients With Fever of Unknown Origin

By Milana Bogorodskaya, MD

In a recent study published in Open Forum Infectious Diseases, Fisher et al. evaluated the clinical utility of a labeled white blood cell scintigraphy (WBCS) in patients undergoing an evaluation of fever of unknown origin. The authors conducted a retrospective, single-center study of 132 patients (91% hospitalized) who had a WBCS performed for fever or sepsis of unknown origin between 2015 and 2019.

Of the 132 patients who received a WBCS, 50 scans (38%) had a positive finding that could explain the fever of unknown origin. Of these 50 scans, nine (18%) were deemed to be false negatives, and 31 (62%) were deemed to be false positives, five of which led to unnecessary procedures. Only 19 (38%) were confirmed as true positives, as determined by one of the study authors who corroborated the positive WBCS finding to relevant pathology, microbiology, and imaging in the patients’ charts. Of the 19 true positive WBCS findings, the authors reported that 10 (52%) already had the diagnosis shortly after based on the results of tests not ordered because of WBCS findings. In another two patients, WBCS results were ignored as they did not change clinical management, and in another three, a computed tomography scan was enough to establish diagnosis. Although the authors described two cases in which WBCS was deemed to be clinically useful in the evaluation of fever, in one of the cases, WBCS guided the clinicians toward the diagnosis of pneumonia while the patient had fungal sinusitis. The other was a case of osteomyelitis for which magnetic resonance imaging results were equivocal.

There are multiple limitations to this study, including its descriptive nature, lack of a comparator group, and lack of a definitive diagnosis in more than half of the cases. Nevertheless, this study demonstrates the poor sensitivity and specificity of WBCS in patients presenting with fever of unknown origin and highlights the potential harms that can be associated with false positive and false negative results. 

(Fisher et al. Open Forum Infect Dis. 2022;9(3):ofac015.)

 

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