Single vial preparation of 99mTc ciprofloxacin for the detection of extra pulmonary tuberculosis

Tuberculosis (TB) remains one of the most common causes of musculoskeletal infection in many parts of the world. The deep-seated bony tubercular lesions are rather difficult to diagnose and the procedures are generally traumatic. The conventional anatomical imaging modalities such as plain radiography, ultrasonography, and computed tomography are useful only after abscess formation, which is a later manifestation of the infection. The role of Gallium (⁶⁷Ga) imaging in picking up pulmonary, extra pulmonary and skeletal tuberculosis has been demonstrated. The use of radiolabelled antibiotics presents a promising approach for the precise diagnosis and detection of infectious lesions, because they specifically bind to the bacterial component, making it possible to differentiate between infectious and sterile lesions. In view of this, the present study was carried out prospectively to evaluate the clinical utility of a single vial kit preparation of ^99mTc-ciprofloxacin (Brand name-Diagnobact™, procured from INMAS, DRDO, New Delhi, India) scintigraphy for localizing the extrapulmonary tubercular infection. Twelve patients (8M, 4F; mean age 23± 11 years) with clinical and radiological evidence of extrapulmonary TB were enrolled for the study and a written informed consent to participate in the study was obtained from all the study subjects. The suspected tubercular osteomyelitis (TBOM) sites were tibia - 2 patients, vertebrae-2 patients, elbow-1 patient, hip joint-4 patients, shaft of femur 2 patients and soft tissue (gluteal muscles) - 1 patient. Three-phase bone scintigraphy was performed in all the patients after i.v. injection of 15.0 mCi of ^99mTc-MDP. Diagnobact ™ scanning was performed after i.v. injection of 15.0 mCi of ^99mTc-Ciprofloxacin. Static images were acquired at 1-h, 4-h & 24-h. The anterior and posterior scintigraphic images were performed under the dual headed gamma camera (ECAM). The Diagnobact scan was interpreted positive for active bacterial infection if the lesion to background ratio increased until 24-h whereas, a plateau or reducing ratio represented inflammation. The diagnosis of TB in all the patients was confirmed either on PCR (9 patients) or microbial culture (3 patients). The results of the scintigraphy indicated that ^99mTc-MDP scans were positive in all (12/12), whereas, the Diagnobact scanning was positive in 10 (10/12) patients. The remaining 2/12 patients of suspected vertebral TBOM were negative on Diagnobact scanning. The sensitivity and specificity of the ^99mTc-Diagnobact scanning to pick up extrapulmonary TB in the present study was 83% each. The PPV was 100% and the diagnostic accuracy of the procedure was 83%. It is thus concluded that Diagnobact ™ like Infecton is able to pick up tubercular lesion in bone and soft tissue. However, the efficacy of this radiopharmaceutical in extrapulmonary TB needs to be further evaluated in a larger number of patients.