EVALUATION OF SEQUENTIAL THALLIUM AND GALLIUM SCANS OF THE CHEST IN AIDS PATIENTS

With decreasing incidence of pneumocystis carinii pneumonia (PCP) in A IDS as a result of prophylactic regimens, there is a higher incidence of tuberculosis (TB), mycobacterium avii complex (MAC), kaposi sarcoma and malignant lymphoma, There is a need for differentiating these var ious pathological entities, The purpose of this study was for a retros pective evaluation of sequential thallium and gallium scans in AIDS pa tients for differentiating intrathoracic kaposi sarcoma from malignant lymphoma and opportunistic infections, Methods: A total of 181 patien ts had both studies completed between March 1992 and May 1994, The fin al diagnosis was verified only in 83 patients, Results were correlated with the CD4 counts, bronchoscopic and chest radiograph findings, Res ults: In patients with pulmonary kaposi sarcoma and no opportunistic i nfections (19 patients), a thallium-positive, gallium-negative pattern was detected in 17 patients with a sensitivity of 89%, In the presenc e of kaposi sarcoma plus opportunistic infections, this pattern was on ly detected in 7 of 19 patients (sensitivity dropped to 37%), In 45 pa tients with opportunistic infections and no kaposi sarcoma, only two f alse-positive findings were found in patients with cytomegalic virus p neumonia for a specificity of 96%, For the whole group of 83 patients, sensitivity was 63%; specificity 95%; positive predictive value 92%; accuracy 81%; and negative predictive value 75%, Conclusion: A thalliu m-positive, gallium-negative pattern in AIDS patients has a high speci ficity for the diagnosis of kaposi sarcoma, however, the sensitivity d ropped from 89% to 37% in the presence of opportunistic infections.