CRA56 POSITIVE QUANTIFERON MASKS DIAGNOSIS

Introduction:

Tuberculosis (TB) remains a significant public health challenge, particularly in developing and least developed countries. About 15-20% of TB cases are extrapulmonary, affecting various organs and often mimicking malignancies. This necessitates a thorough diagnostic workup to distinguish between TB and other serious conditions.

Case Report:

A 56-year-old Somali woman presented with chronic abdominal pain for 9 months, followed by symptoms of subacute intestinal obstruction. Initial investigations revealed a positive QuantiFERON test, and a CT scan of the abdomen showed a bladder mass with involvement of the colon and uterus. Given the high prevalence of TB in Somalia and her critical condition, she was empirically started on anti-TB treatment. She underwent exploratory laparotomy with ileostomy. Histopathology of peritoneal lesions and bladder tissue revealed features of metastatic micropapillary urothelial carcinoma.

Discussion:

The QuantiFERON-TB Gold test detects Mycobacterium tuberculosis infection but cannot distinguish between latent and active TB. In this case, the positive QuantiFERON test misled the initial diagnosis towards TB, delaying the correct identification of metastatic urothelial carcinoma. The overlap in clinical and radiological features between TB and malignancies like urothelial carcinoma can complicate diagnosis. Combining multiple diagnostic approaches such as biopsy histology, polymerase chain reaction (PCR) assays, and culture techniques can significantly improve diagnostic accuracy in such complex cases. 

Conclusion:

This case underscores the potential for misleading positive QuantiFERON results, which can obscure the correct diagnosis of conditions like malignancy. High clinical suspicion and comprehensive diagnostic approaches are essential, especially in high-risk patients, to prevent misdiagnosis and ensure appropriate treatment. This case highlights the importance of considering alternative diagnoses and using multiple diagnostic tools to achieve an accurate diagnosis.