One-day protocol versus two-day protocol in acquisition of scintigraphy with "in vitro" labelled white blood cells for diagnosis of osteoarticular infection. / Protocolo de un día vs protocolo de dos días de adquisición mediante gammagrafía con leucocitos marcados in vitro para el diagnóstico de infección osteoarticular.

ABSTRACT

INTRODUCTION: It is difficult to determine osteoarticular infection and differentiate inflammation from infection with laboratory and imaging procedures (CT, MRI, US). Labelled white-blood-cell scintigraphy (WBCS) is the nuclear medicine test of choice but it takes two days, sometimes finds it difficult to differentiate soft tissue from bone infection and therefore causes interobserver variability, which decreases its specificity. OBJECTIVE: To demonstrate the usefulness of the one-day protocol with time decay-corrected acquisition in WBCS to diagnose osteoarticular infection and to reduce interobserver variability. The role of SPECT/CT in WBCS in locating the infected focus was also evaluated. METHODS: 110 patients with suspected osteoarticular infection were studied prospectively. Planar images were obtained with time decay-corrected acquisition at 30min, 4h, 8h and 24h. WBCS planar images were grouped in two protocols One-day protocol experts evaluated 30min, 4h and 8h images. Two-day protocol experts evaluated 30min, 4h and 24h images. Both protocols were classified as SPECT/CT was performed in 72 patients. Kappa index was calculated to evaluate interobserver variability. RESULTS: Infection was confirmed in 34 cases. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy were 97.1%, 97.4%, 94.3%, 98.7%, and 97.3% for the one-day protocol and 94.1%, 97.4%, 94.1%, 97.4%, and 96.4% for two-days-protocol. SPECT/CT contributed to diagnosis in 45/50 patients with planar WBCS positive. Kappa index 0.8 for one-day protocol and 0.79 for two-day protocol, respectively. CONCLUSION: One-day protocol with time decay-corrected acquisition WBCS and SPECT/CT enables early and accurate diagnosis of osteoarticular infection.