Diagnostic Efficacy of Tagged White Blood Cell Scans in the Workup of Occult Infection

1University of Michigan, Ann Arbor, Ml
2University of Michigan, Ann Arbor, Ml
3University of Michigan, Ann Arbor, Ml

Meeting: Hospital Medicine 2009, May 14-17, Chicago, Ill.

Abstract number: 31

Background:

Tagged white blood cell scans (TWBCSs) are often used as a diagnostic study when searching for an occult infection after most other studies have been performed. These studies are not inexpensive, averaging near $400 per study at our institution. Little is known about how often these scans yield new information that was not known from previous studies or information that affects management.

Methods:

We looked at every adult patient who underwent a TWBCS for the 2 years between August 2004 and August 2006, resulting in 498 scans. We excluded all patients who underwent the scan for follow‐up of known tumor (239 patients), as well as those who underwent the scan to look for a specific infection, for example, postoperative wound infections or osteomyelitis (189 patients). This left 70 TWBCSs, of which 1 was excluded as no patient data were available, and 1 patient underwent 2 TWBCSs. We then looked at specific parameters of the 68 cases analyzed, including presence of fever, leukocytosis, and bloodstream infections, to assess whether any of these were useful predictors of cases in which TWBCS could yield further diagnostic information.

Results:

The mean age of patients analyzed was 54.1 ± 17.7 years, with 38 men (59.4%). Forty scans were specifically ordered by infectious disease physicians, others from a variety of sources. Patients had a wide range of issues prompting a scan, and the TWBCS was generally done after other tests had been completed. Fever was present for 35 cases (51.5% of scans), with range of days of fever from 1 to 120 days (median was 7 days); leukocytosis was present in 46 cases (67.6%); and persistent bloodstream infection was present in 36 cases (52.2%). The TWBCS changed the outcome in only 16 cases (23.5%). In the 16 patients for whom the TWBCS made a difference in clinical management, 11 had bloodstream infections. Among the 16 cases for whom the result changed the management, 4 were normal, and 12 were abnormal. Staphylococcus aureus was the most important pathogen in those with persistent bloodstream infection with 15 cases (14 MRSA and 1 MSSA). Forty‐one of 68 scans (60.3%) were actually abnormal, with the remainder normal. Comparing the odds of being abnormal in the setting of Staphylococcus aureus bacteremia compared with all other cases showed an OR of 5.8 (Cl 1.2–28.3), P = 0,03. Among these 15 cases, 13 scans were abnormal (86.7%). However, among these 13 abnormal scans, the TWBCS only changed management in 4 patients.

Conclusions:

The TWBCS is a nuclear medicine study that is often ordered in the workup of occult infection. Our data indicate that this study is of highest diagnostic yield in cases in which patients had persistent bloodstream infections, particularly those with persistent Staphylococcus aureus bacteremia. The TWBCS may also be a reasonable alternative in those with impaired renal function limiting the use of contrast‐enhanced CT scans.

Author Disclosure:

J. G. Dastidar, none; S. K. Cinti, none; P. Malani, none.

To cite this abstract:

Dastidar J, Malani P, Cinti S. Diagnostic Efficacy of Tagged White Blood Cell Scans in the Workup of Occult Infection. Abstract published at Hospital Medicine 2009, May 14-17, Chicago, Ill. Abstract 31. Journal of Hospital Medicine. 2009; 4 (suppl 1). https://www.shmabstracts.com/abstract/diagnostic-efficacy-of-tagged-white-blood-cell-scans-in-the-workup-of-occult-infection/. Accessed May 26, 2019.

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