Differential diagnosis of septic and aseptic bone lesions of the foot in patients with diabetic foot syndrome: the potential of using a standardized uptake value with osteotropic radiopharmaceuticals

Aim. The study was conducted to calculate standardized uptake values (SUVs) for foot bones, determine the optimal SUV type in patients with degenerative changes, and assess the potential of quantitative single-photon emission computed tomography (SPECT/CT) in patients with diabetic foot syndrome (DFS) complicated by osteomyelitis.

Materials and methods. The study design was prospective. Patients with a documented clinical diagnosis of diabetic foot and confirmed or suspected osteomyelitis underwent SPECT/CT scanning after intravenous injection of the radiopharmaceutical (^99mTc – Pyrophosphate). The calculation of standardized uptake values – mean SUV (SUVmean), maximum SUV (SUVmax), and peak SUV (SUVpeak) – was performed using the SyngoVia software. To calculate the threshold standardized uptake value, receiver operating characteristic analysis (ROC) was conducted, followed by the calculation of the area under the ROC curve (AUC).

Results. Forty-eight patients were examined: 28 people with septic foot lesions and 20 individuals with aseptic foot lesions. Calculations revealed no statistically significant differences between the SUV values (max, mean, and peak) for septic and aseptic lesions. However, the standardized uptake value normalized by lean body mass (SUVlbm (max)) demonstrated the largest ROC AUC. A threshold value for differentiating between pathological and healthy bone tissues was 1.64, with sensitivity of 93.5% and specificity of 95.6%. The threshold value for distinguishing between septic and aseptic inflammations in patients with diabetic foot syndrome was 4.35, with sensitivity of 82.4% and specificity of 80.3%.

Conclusion. The study confirmed that the use of SUVlbm (max) threshold value of 4.35 (Se = 82.4%; Sp = 80.3%; AUC = 0.883) is possible for the differential diagnosis of osteomyelitis and Charcot foot in patients with diabetic foot syndrome. Additionally, to confirm inflammation, a SUVlbm (max) threshold value of 1.64 (Se = 93.5%; Sp = 95.6%; AUC = 0.983) is applicable.

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