PREDICTIVE VALUE OF COMPUTED TOMOGRAPHY-BASED DIAGNOSIS OF INTRACRANIAL TUBERCULOMAS

THE NEED TO obtain histological diagnoses of intracranial tuberculomas , before initiating therapy, is not universally accepted, because some clinicians believe that an image-based diagnosis is fairly accurate i n patients from endemic regions. To evaluate the sensitivity, specific ity, and predictive value of computed tomography (CT)-based diagnosis of an intracranial tuberculoma, we prospectively compared the preopera tive imaging diagnoses with histological diagnoses in 105 consecutive patients with intracranial masses. CT differential diagnoses (first or second) of tuberculomas were considered in 21 patients. Seven of them were histologically confirmed to have tuberculomas (true-positive res ults); 14 had other diseases (false-positive results). The 14 false-po sitive cases included 6 cases of astrocytomas, 5 of metastases, and 3 with miscellaneous diagnoses. All tuberculomas were correctly diagnose d on the CT scans (5 by both surgeons and 2 by one surgeon). During th e study period, we encountered 11 patients who were referred by other clinicians with diagnoses of tuberculomas on the basis of their CT sca ns. We concurred with their CT diagnoses in 5 of them, but only 1 pati ent had a histologically verified tuberculoma. Astrocytomas (4 patient s), metastases (3 patients), and solitary cysticercus granulomas (3 pa tients) were the causes of misdiagnosis in this group of patients. Alt hough the sensitivity of CT in the diagnosis of intracranial tuberculo mas is 100%, and its specificity is 85.7%, the positive predictive val ue is only 33% (confidence limits, 24-42%). The negative predictive va lue is 100%. The low positive predictive value for a diagnosis of intr acranial tuberculoma on CT alone indicates the need for a confirming h istological diagnosis.