Handling of Doubtful WBC Scintigraphies in Patients with Suspected Prosthetic Joint Infections

Abstract

Despite the application of EANM recommendations for radiolabelled white-blood-cells (WBC) scintigraphy, some cases still remain doubtful based only on visual analysis. The aim of this study was to investigate the role of semi-quantitative analysis and bone marrow scan (BMS) in solving doubtful cases. We retrospectively evaluated all [99mTc]HMPAO-WBC scintigraphies performed, in the last 7 years, for a suspected monolateral prosthetic joint infection (PJI). In doubtful cases, we used five different thresholds of increase of target-to-background (T/B) ratio, between delayed and late images, as criteria of positivity (5%, 10%, 15%, 20% and 30%). BMS were also analysed and sensitivity, specificity and accuracy of different methods were calculated according to final diagnosis. The sensitivity, specificity and accuracy were, respectively, 77.8%, 43.8% and 53.0% for the cut-off at 5%; 72.2%, 66.7% and 68.2% for the cut-off at 10%; 66.7%, 75.0% and 72.7% for the cut-off at 15%; 66.7%, 85.4% and 80.3% for the cut-off at 20%; 33.3%, 93.8% and 77.3% for the cut-off at 30%. BMS provided a significantly higher diagnostic performance than 5%, 10% and 15% thresholds. Conversely, we did not observe any statistically significant difference between BMS and the cut-off of more than 20%. Therefore, doubtful cases should be analysed semi-quantitatively. An increase in T/B ratio of more than 20% between delayed and late images, should be considered as a criterion of positivity, thus avoiding BMS.

Semi-quantitative analysis with 99mTc-Besilesomab in musculoskeletal system infections

“… Lauri et al (2020) described different cut-off points in labeled leukocyte scintigraphy with doubtful results in the visual analysis, concluding that a 20 % increase in activity provided greater precision, but to date there are no studies on this topic with Besilesomab. Authors of quantitative studies and clinical practice guidelines define a test as positive when the count is increased by ≥10 % ( i.e.…”

99mTc-HMPAO-WBC SPECT/CT versus 18F-FDG-WBC PET/CT in chronic prosthetic joint infection: a pilot study

“…99m Tc-HMPAO-WBC scintigraphy shows a significant inflammatory uptake for at least 6 months after arthroplasty [44]. A separate scan visualizing the bone marrow (e.g., 99m Tc-nanocolloid scintigraphy or SPECT/CT) [45,46] can differentiate infectious from a normal reactive uptake caused by tissue healing following surgery. Another way to visualize this is through early leukocyte imaging at 30 min after injection [16].…”

importância de leucócitos marcados no diagnóstico por imagem em infecções articulares periprotéticas / The value of labeled leukocytes imaging for periprosthetic joint infection diagnosis

“…Além disso, artigos encontrados nesta revisão evidenciam a importância da utilização da imagem híbrida SPECT/ CT para a solução de dúvidas em análise qualitativa, pois permite uma boa visualização anatômica e da extensão da infecção do local com excelência, podendo ser o diferencial necessário para a definição de diagnóstico do caso e, consequentemente, aumentando a sensibilidade e especificidade do exame (16,17) .…”