FLOW CYTOMETRIC SCREENING FOR RENAL PATIENTS.
A.W. Harmer, A.J. Heads, R.W. Vaughan. South Thames Tissue
Typing, Guy's Hospital, London, UK.
Flow cytometric screening using pooled cells has been
a standard method for screening sera from renal patients in this laboratory
for over 4 years. The aim of this study was to review the results of flow
screening of a large series of consecutive samples. Samples are assigned
to flowscreen if the patient has previously been found to have no HLA specific
antibodies, if the patient is new or returning to the transplant waiting
list. Positive samples are then further screened by cytotoxicity (CDC)
and/or ELISA (PRA-STAT). A total 2009 samples were analysed. There were
402 positive samples from 254 patients and 18 positive quality control
samples. Analysis of the patients with positive samples showed that 134
had previous failed transplants. CDC screening showed positive results
for 67 patients but was negative for 67 patients. In all 21 of the 67 CDC
negative, flowscreen positive patients tested by PRA-STAT the presence
of HLA specific antibodies was confirmed, samples from the remaining 46
patients are awaiting PRA-STAT screening. Of the patients with no previous
transplants analysis of other sensitising events and additional screening
showed that unexplained flowscreen positive results were found in 51 patients,
18 of which had at least 2 further flowscreen negative samples and 14 of
which were reproducibly positive in at least 3 samples, the remainder require
testing of further samples. In conclusion the flowscreen detected IgG antibodies
in 50% of patients with failed transplants which were not detected by CDC,
demonstrating the importance of using a sensitive screening method for
these patients.