I am comparing Guidelines for Prenatal and Perinatal Immunohematology and the Technical Manual to nail down some info on titrations. I am confused by the Fact that the Guidelines on p 13 lists the 15th ed of the Tech Manual "(pp761-4--method 3-7)" as the reference for the titration method, but this method is not the one under the HDFN methods chapter of the Tech Manual that references John Judd's papers (method 5-3). It also does not suggest measured volumes of test constituents as the 5-3 does. The method that is referenced in the Guidelines (3-7) lists no references in the Technical Manual so I don't know its source. It is the method that includes determining a score with the titer, but Guidelines never mentions that. Sorry if this is confusing. You might want to look at the respective books to see what I am talking about.

Does John Judd recommend turning out a score with titrations for OBs? Has he ceased recommending we use measured volumes? How many places use method 3-7 for prenatal titers, and why?

We recently switched to the method referenced in CAP's 2008 ABT-B survey:

Archives of Pathology and Laboratory Medicine: Vol. 132, No. 7, pp. 1194–1201. Reducing the Variation in Performance of Antibody Titrations

http://arpa.allenpress.com/pdfserv/10.1043%2F1543-2165(2008)132%5B1194:RTVIPO%5D2.0.CO%3B2

Linda Frederick

So you use gel now for your titres Linda? We did for a while but found we were sometimes 2 tubes higher than the other lab the obstetricians were getting reports from. We switched back when our provincial proficiency test sent out a sample - we got 3 tubes higher and they stated the tube IAT method in AABB technical manual was the "gold standard".

No, we still use tube. We used to just add a drop of reagent red cells to each, now we use a calibrated pipette to deliver 50ul as the article recommends (big difference? I don't think so).

And, we used to use a 1+ positive as the end point, now we use "W+, macroscopic" as suggested in the article. I personnally call anything you can see macroscopically 1+, so this really isn't much change either.

LF

We recently had an "Unacceptable" on one sample of the recent CAP Titration Survey (our results were one dilution tube too high), so we also have switched to the CAP's recommended "Universal Procedure" for our titrations. Everything that Linda mentions in her above posting rings true for us, too. (So, we'll see how the next survey goes......)

I just read that article - I have one kudo and that is the volumes. If you use 0.05 mL red cell suspension and 0.10 mL specimen ISN'T THAT A 1:3 DILUTION (0.15/0.05)? Unless you wash your red cells to a dry button don't you have to take the diluent in the red cells into account? I also agree with bbirder that if I can see it macro, I call it 1+. Just food for thought . . .

Even if it is a dilution, that's the same dilution that one drop of cell suspension and 2 drops of sample always have given us--including whomever did the original research that set 16 up as a critical titer for anti-D. This method is just measured volumes so it is more consistent. It looks like it is less work than Judd's method of making a 2% suspension.