Diagnosing osteomyelitis in the diabetic foot: a pilot study to examine the sensitivity and specificity of Tc(99m) white blood cell-labelled single photon emission computed tomography/computed tomography

Diabetic foot ulceration poses a significant threat of osteomyelitis (OM) and subsequent amputation. The diagnosis of OM via imaging studies is difficult as radiographic findings do not present immediately and advanced imaging studies may be contraindicated or unavailable. A novel diagnostic tool has been developed which synthesises technetium-99 white blood cell-labelled single-photon emission computed tomography and computed tomography (Tc(99m) WBC labelled-SPECT/CT) imaging, effectively enhancing anatomic detail. The aim of this pilot study was to determine the validity and reliability of this novel imaging technique in patients with diabetic foot ulcers in a Veterans Affairs healthcare facility. A retrospective review was performed on consecutive patients who met the inclusion criteria (n = 14) and underwent Tc(99m) WBC-labelled SPECT/CT for suspected OM. Histopathologic analysis of bone specimen (when available) and International Working Group on the Diabetic Foot consensus criteria were used as a reference standard. The sensitivity and specificity of Tc(99m) WBC-labelled SPECT/CT were 87·50% [confidence interval (CI): 64·58-110·42%] and 71·43% (CI: 37·96-104·90%), respectively. Negative predictive value (NPV) and positive predictive value (PPV) were 83·33% (CI: 53·51-113·15%) and 77·78% (CI: 50·62-104·94%), respectively, with a likelihood ratio (LR) of 3·063 and an accuracy of 80%. These findings suggest Tc(99m) WBC-labelled SPECT/CT can be useful in imaging OM in patients with diabetic foot ulcers.