Elevated D Dimer in the Lungs and Blood of Patients With Sarcoidosis (10)

Although we demonstrated that D dimer could be found simultaneously in the lungs and blood of some patients with sarcoidosis, there were some in whom D dimer was found in only the lungs or the blood. D dimer may have crossed from the blood into the alveolar space in patients with detectable levels in both compartments. However, BAL and plasma D dimer levels adjusted to total protein levels, and BAL D dimer levels adjusted for the loss of D dimer during BAL fluid concentration showed that patients had 70 to 500 times higher levels of D dimer per milligram of total protein in BAL fluids than in the plasma. These adjustments indicate that most, if not all, of the BAL D dimer was generated within the pulmonary compartment and could have leaked into the systemic circulation. We were surprised to find that the sarcoidosis patient with the highest BAL D dimer levels did not have detectable D dimer in the plasma. It is possible that D dimer in the lungs may not have crossed to the circulation, but this is unlikely, since very high BAL protein levels, suggesting alveolar-capillary leak, were found in this individual. Another possibility is that D dimer may have gained access to the blood but was rapidly degraded so that fibrin fragments with epitopes both to the capture and tag antibodies were absent. Finally, a particular factor in this patients plasma could have inhibited D dimer detection by EIA, but 12 serial dilutions of the plasma did not unmask any inhibitory effect in the D dimer assay.
Bronchoalveolar lavage D dimer was absent in two patients with sarcoidosis who had type 1 and 2 chest radiographs and who were not receiving therapy at the time that BAL was performed. Sampling of lung regions with low fibrin turnover could have explained the absence of D dimer in these cases. Both subjects had detectable D dimer in the plasma that may have been generated in lung regions not sampled by BAL or in extrapulmonary sites of active disease.