Mike Meyer asks, "we run three dilutions for all of our factor testing. Occasionally, we see results in which upon higher dilutions, the factor value decreases after adjusting for the dilution. For instance, I had a case today in which the FIX values were 0.64, 0.55, and 0.43 U/mL for the 1:10, 1:20, and 1:40 dilutions [values corrected for the dilution effect], the opposite effect seen with inhibitors. Calibration curve seems fine." He adds, "the patient’s FVIII level was very high [about 3.60 U/mL]. We possibly thought that the higher dilutions would bring the FVIII level back closer to a more normal range. The high concentration of FVIII in the first dilution may be accelerating the PTT clotting time yielding a falsely higher FIX value. Please comment."
Posts - Validation
Oct 23, 2020 12:44pm
Oct 28, 2019 2:06pm
From Heather DeVries, Indiana University: I’ll make this one short and sweet…how many samples should be used in a cumulative summation study?
Jun 29, 2019 10:33am
From Maureen (Mo) Tacke, St Luke's Health System: Hi George, our institution is coming to the joyous time of lot roll over in coagulation, and it’s got me wondering... Is our process a little (or a lot) overkill? Current process: Normal ref range studies (20 normals) for PT , PTT , FIB, AT , TT , PC , PS , DRVVT , SCT, APCR , factor VIII, factor IX, VWF activity, VWF antigen Lot to Lot studies (20, spanning the range) for all tests listed above plus D-dimer. Control Studies (assayed controls), 10 runs over a minimum of 5 days.