Effect of microbes on Patterns of Labeled White Blood Cells in Osteomyelitis
Keywords:Bone scan, Gram-negative bacteria, Gram-positive bacteria, labelled white blood cells, osteomyelitis.
Aim: This study investigates the effect of microbiological characteristics of causative organisms on the scintigraphic
patterns of labelledwhite blood cell (WBC) scans in cases of proven osteomyelitis.
Methods: Retrospective analysis of 25 patients referred with suspected osteomyelitis and had both bone and
labelled WBC scans performed and complete records of the microbiological culture of the causative organism.
The bone and labelled WBC scans were retrieved and reviewed by two nuclear medicine physicians. Any definite
focal accumulation of labelled WBCs within the bone was considered positive for osteomyelitis. Diagnosis of
osteomyelitis in the discharge summary was considered the reference standard and was based on a combination
of the clinical scenario, imaging, and laboratory findings including microbiology. A correlation of the pattern of
labelled WBC and the type of microorganisms was done.
Results: A total of 16 patients were included in this study, seven females and nine males. Of these, seven patients
had Gram-positive whereas nine patients had Gram-negative organisms. The majority (85.7%) of Gram-positive
organisms showed increased accumulation of labelled WBCs, whereas only one-third (33.3%) of patients with
Gram-negative organisms had such findings.
Conclusion: The pattern observed in this study shows that the falsenegative results of labelledWBC scans
were mainly noted in patients with Gram-negative as opposed to Gram-positive infections. This confirms the
experimental animal study findings that the secretion of anti-chemotactic factors by Gram-negative organisms,
seems to be inhibiting the migration of labelled WBCs to the site of infection. The inhabitation is decreasing the
accumulation of labelled WBCs and consequently resulting in a falsenegative finding. The study adds to evidence
that microbiological characteristics of the causative organisms are another explanation for the falsenegative WBC
in proven osteomyelitis.
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