Estimation of res-function before and after plasma-pherese using 99T-labelled microcolloid

Experience todate has shown that the method we have used for estimating the RES clearance activity furnishes fully reproducible results (important for accurate pre- and postseparation comparisons). It is not excessively demanding for the patient and does not require prolonged immobilization, because it merely involves the injection of the tracer and the withdrawal of blood at defined sampling times. Results available suggest that in patients showing clinical improvement after plasmapheresis the rate and quantitiy of tracer extraction from the blood are increased, as is reflected by the reduced Tsub(eff)and the increased initial-phase component (in percent of total function). In one patient, who was in a poorer condition after plasma separation, clearance was found to be reduced and proceeded at a slower rate (Tsub(eff) prolonged and % inital phase reduced). Our case without clinical change showed virtually no changes in pre-versus postseparation clearance. Pending confirmation in a larger patient material, the results would seem to support the concept of an (unspecific) deblockade of the RES by plasmapheresis (removal of circulating pathogenic immune complexes). The tracer extraction from the blood can be described by 2 exponential functions: (1) a rapid inital phase of about 90% and a Tsub(eff) of 30 minutes and (2) a slow phase of about 10% of the total function and a Tsub(eff) of about 18 hours. This plasma disappearance rate was derived from 2 normal subjects. To estimate the RES clearance activity in our patients, the changes (increase or decrease) of the first-phase component versus normal (90%, Tsub(eff) 30 min.) were used as an indicator. (Author)