Utility of ^99mTc-ubiquicidin scintigraphy in diagnosis of orbital aspergillosis

Aspergillosis is a fungal disease with a wide range of clinical manifestations that poses the greatest risks to immunocompromised patients. The diagnosis of Aspergillosis becomes challenging especially in odd sites like the orbits. Antimicrobial peptides like ubiquicidin show high specificity for bacterial and fungal infections. The present study was conducted to evaluate the feasibility of ^99mTc-Ubiquicidin scintigraphy in the diagnosis of Orbital Aspergillosis. Images of five male patients (mean age = 55.2 years; age range = 32–62 years) with suspected Aspergillosis were reviewed in this retrospective study. Patients were injected with ^10mCi of ^99mTc- UBI intravenously. A dynamic image was acquired followed by subsequent static views taken at 15 min, 30 min, 45 min, 1 hour, and 2 hour post-injection. To study the biodistribution, whole-body anterior and posterior images were acquired at 1 hr; SPECT/CT was performed in 4 patients. Scans were interpreted as true positive, false-positive, true negative, or false-negative based on histopathological evaluation, imaging findings (CECT/ MRI), and clinical follow-up as the gold standard. Of the five studies included in the analysis, uptake was seen in 4 patients. 3 were true positive, 1 was false negative, and 1 was true negative for the diagnosis of aspergillosis. Thus, the scan showed sensitivity and specificity for the diagnosis of aspergillosis to be 75 percent and 100 percent, respectively. The study's positive predictive value (PPV) and negative predictive value (NPV) were 100% and 50%, respectively. The overall accuracy of ^99mTc-UBI scintigraphy for attributing infective etiology to the lesions was 80%. Conclusion: Where there is a high index of suspicion for fungal etiology of orbital lesions, our study suggests that ^99mTc- UBI scintigraphy with SPECT/CT appears to be a promising modality, in attributing infective causality, though larger studies are necessary. (author)