ROLE OF PULMONARY-FUNCTION IN THE DETECTION OF ALLOGRAFT DYSFUNCTION AFTER HEART-LUNG TRANSPLANTATION

Background - Lung function is altered by infection and rejection in pa tients who undergo heart-lung transplantation. The sensitivity, specif icity, and positive/negative predictive values (PPV and NPV) of lung f unction for the detection of allograft dysfunction in these patients w ere measured. Methods - Thirty three patients who underwent heart-lung transplantation were followed for a mean period of 16.3 months. On 12 3 occasions functional measurements were obtained at the time a transb ronchial biopsy specimen and/or bronchoalveolar lavage fluid was taken , which were used as gold standards. Optimal sensitivity (the value fo r which sensitivity equals specificity) was computed for each function al test from receiver-operator characteristic (ROC) curves. Results - Acute rejection was present on 31 occasions and infection on 36 occasi ons; 56 samples were normal. Infection and rejection were accompanied by airflow obstruction, a rise in the slopes of the alveolar plateaus for nitrogen, hexafluoride sulphur and helium (SN2, SSF6, and SHe), an d a decrease in the difference between SSF6 and SHe (Delta S), total l ung capacity (TLC), and lung transfer factor (TLCO). Optimal sensitivi ties for SHe, mid forced expiratory flow (FEF25-75), TLC, and forced e xpiratory volume in one second (FEV1) were 68%, 67%, 66%, and 60%, res pectively; they were not different for infection and rejection and did not change over the study period. For infection and rejection togethe r, PPV ranged from 72% to 88% and NPV from 27% to 52% according to the functional test and the postoperative period considered. Conclusions - Indices of ventilation distribution, FEF25-75, and TLC have the best optimal sensitivity for the diagnosis of infection and rejection afte r heart-lung transplantation. The high PPV of pulmonary function in de tecting allograft dysfunction observed in this study suggests that a d iagnostic procedure should be performed whenever one or more functiona l tests deteriorate; conversely, the low NPV indicates that a stable p ulmonary function does not rule out allograft dysfunction.