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Background: Acute rejection remains a major source of morbidity after lung transplantation. Given the importance of this diagnosis, an international grading system was developed to standardize the diagnosis of acute lung-allograft rejection. The reliability of this grading system has not been adequately assessed by previous studies., Methods: We examined the level of agreement in grading transbronchial biopsy specimens obtained from a large multicenter study (AIRSAC [Comparison of a Tacrolimus/Sirolimus/Prednisone Regimen vs Tacrolimus/Azathioprine/Prednisone Immunosuppressive Regimen in Lung Transplantation] trial). Biopsy specimens were initially graded for acute rejection and lymphocytic bronchiolitis by the site pathologist and subsequently graded by a central pathologist. Reliability of interobserver grading was evaluated using Cohen κ coefficients., Results: A total of 481 transbronchial biopsy specimens were graded by both the site and central pathologists. The overall concordance rates were 74% and 89% for grade A and grade B biopsy specimens, respectively. When samples from biopsies performed at different time points after transplantation were assessed, there was a higher level of agreement early (≤ 6 weeks) after transplant compared with later time points for acute rejection. However, there was still only moderate agreement for both grade A (κ score 0.479; 95% CI, 0.29-0.67) and grade B (κ score 0.465; 95% CI, 0.08-0.85) rejection., Conclusions: These results expand upon previous reports of interobserver variability in grading transbronchial biopsy specimens after lung transplantation. Given the variability in grading these specimens, we advocate further education of the histopathologic findings in lung transplant biopsy specimens, as well as revisiting the current criteria for grading transbronchial biopsy specimens to improve concordance among lung transplant pathologists., Trial Registry: ClinicalTrials.gov; No. NCT00321906; URL: www.clinicaltrials.gov.

Unlabelled: With decreasing incidence of pneumocystis carinii pneumonia (PCP) in AIDS 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 various pathological entities. The purpose of this study was for a retrospective evaluation of sequential thallium and gallium scans in AIDS patients for differentiating intrathoracic kaposi sarcoma from malignant lymphoma and opportunistic infections., Methods: A total of 181 patients had both studies completed between March 1992 and May 1994. The final diagnosis was verified only in 83 patients. Results were correlated with the CD4 counts, bronchoscopic and chest radiograph findings., Results: In patients with pulmonary kaposi sarcoma and no opportunistic infections (19 patients), a thallium-positive, gallium-negative pattern was detected in 17 patients with a sensitivity of 89%. In the presence of kaposi sarcoma plus opportunistic infections, this pattern was only detected in 7 of 19 patients (sensitivity dropped to 37%). In 45 patients with opportunistic infections and no kaposi sarcoma, only two false-positive findings were found in patients with cytomegalic virus pneumonia 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 thallium-positive, gallium-negative pattern in AIDS patients has a high specificity for the diagnosis of kaposi sarcoma, however, the sensitivity dropped from 89% to 37% in the presence of opportunistic infections.

Diffuse intense lung uptake of TI-201 chloride without abnormal Ga-67 citrate in a case of cytomegalovirus pneumonitis in a patient with AIDS is presented. An autopsy performed within 4 days of imaging revealed no pulmonary pathology other than diffuse cytomegalovirus infection with abundant histiocytes and inclusion bodies and pulmonary congestive heart failure. Among the various mechanisms of TI-201 accumulation, active transport through Na-K ATPase appears to be predominant in this case, as suggested by innumerable histiocytes. It is the authors' experience that positive TI-201 uptake without abnormal Ga-67 accumulation is highly specific for pulmonary Kaposi sarcoma. The presence of such discrepancy between TI-201 and Ga-67 uptake in AIDS patients decreases the specificity of a TI-201 positive/Ga-67 negative lesion for pulmonary Kaposi sarcoma, especially with the rising incidence of both cytomegalovirus and Kaposi sarcoma in AIDS patients.

Diffuse Tl-201 uptake in the lungs could be because of cardiac, neoplastic, inflammatory, or interstitial lung disease. Examples from the different categories, differential diagnosis, and different patterns are presented. The authors discuss the different mechanisms of increased Tl-201 uptake in the lungs which vary according to the underlying pathology.

Five patients with AIDS with Pneumocystis carinii pneumonia (PCP) showed diffuse bilateral lung uptake on sequential thallium and gallium scans. This creates a problem in the sequential use of these tests for the differentiation of Kaposi's sarcoma from acute inflammatory or other malignant diseases. In Kaposi's sarcoma, thallium uptake is usually focal and not diffuse unless associated with other pathology. However, in PCP the diffuse thallium lung uptake may be due to congestion, increased vascular permeability, and extravasation of thallium into the lung parenchyma.