Scottie, We run the B-D HLA-B27 test routinely now as a screen test. We do approximately 200 tests per month, as a regional test center. In the initial stages we ran 2-300 samples with parallel serologic histocompatibility testing. This established a "gray-zone" surrounding the B-D positive/negative cutoff, in which we found almost all of the B7 and other cross-reactions, as well as the very rare (<< 1%) false negatives. We now only send about 5% (gray-zone) of our samples for serologic/molecular typing. A comparison to the Lambda One antibody in the "gray-zone" was also done. This antibody performed well in ruling out B7 cross-reactions. However, it was not cost effective to add it to the screening protocol. We run occasional positive controls (1 or twice a month). They are always positive, because they are selected from known patients in the histocompatibility lab. Hope this helps. Denis Denis Snider Ph.D., F.C.A.C.B. Associate Professor Dept. of Pathology and Molecular Medicine McMaster University -----Original Message----- From: Sparks, Scottie [SMTP:SSparks@unch.unc.edu] Sent: Wednesday, September 01, 1999 12:59 PM To: Cytometry Mailing List Subject: HLA-B27 Testing Questions We are interested in performig HLA-B27 testing by Flow. We are evaluating BD's B27 Kit and it seems to work well. Our questions are concerning controls: How often are positive controls run by those of you perfoming this test clinically? Do you have a way to preserve positive control blood that has worked for you? Also, what have you learned about cross-reactions (like B7)? Thank you in advance for your help! Scottie
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