Antibody Titers

[BankerGirl]

We received an antibody titer resut from our reference lab that had a titer score reported along with the antibody titer. I am having trouble understanding what the score means. The titer was 1, but the score was 13. How do you get a score that high when the titer is only 1? Can someone help me understand this new (to me, anyway) score result? How is it determined and are there any references I can read? I checked the technical manual and was unable to locate anything on this.

Thanks

[Marilyn Plett]

Score is a way of evaluating the strength of an antibody by taking into account both the agglutination strength and the dilution in which reactivity appears. Here's one link that I found; I suspect there are others in standard texts.

http://cls.umc.edu/COURSES/CLS325/Week%2016/HDN1.ppt

[John Eggington]

Take a look at this, too;

http://www.bbts.org.uk/PDFs/events/D%20Bruce%20Antenatal%20monitoring%20of%20anti-D%20and%20c.pdf

Also, I'm sure the AABB technical manual does give information on 'titre scores' (I don't have a copy to hand, so can't be more specific), maybe you could try another look?

[David Saikin]

13 seems a pretty high score for a titer of one . . . I'd ask the reference lab for their scoring method.

[Malcolm Needs ☆]

I agree with David.

I had a look at the 13th edition of the AABB Technical Manual (page 679), where examples are given.

There, a 4+ reaction is given a score of 12 (rather than 13), but it would be a pretty unusual antibody that would give a reaction of 4+ in neat plasma, and nothing diluted 1 in 2.

[John Hansen]

I know this post is super old, but I think I know what happened. Maybe this information will still be useful to you. I just learned about titer scores in some continuing education, and then found it in my AABB technical manual in the methods section.

You get scores for all positive reactions. Each strength of reaction gets a different score. In my continuing ed from the American Red Cross, they gave the scores as: 4+ is 12, 3+ is 10, 2+ is 8, 1+ is 5, and +/- is 2. The score is measured differently than the titer. The titer is the reciprocal of the highest dilution showing 1+ reactivity, which would be tube one in your case. But the score is measured out all the way to the endpoint. If this patient had 1+ on tube one, but weak reactions out to the 1:8 dilution, it would give you a score of 13 (5+2+2+2+2).

Hope that helps in the future.

[David Saikin]

Good points - but the titer in this instance was 1, which means it only reacted in the tube with the neat plasma - none of the dilution tubes . . . and as Malcolm pointed out, it is a very unusual ab to give a 4+ rx in one tube and then be negative for the further dilutions.

[John Hansen]

The titer was 1, which means that none of the dilutions had 1+ activity. The original poster never said what the reactions were. I'm assuming that the reaction on tube one was only 1+, and then it is very possible that further dilutions had +/- activity. The 4+ came from Malcolm theorizing another situation that might give a high score.

[Malcolm Needs ☆]

The 4+ came from Malcolm theorizing another situation that might give a high score.

Absolutely; totally theoretical.

[ANORRIS]

I thought I remmebered a while back where the score did not need to be reported any longer????

[BankerGirl]

Well, as I stated in my original post, this was performed by our reference lab (Red Cross) and they did not tell me the reactions in all the tubes. I did find the explanation in the Technical Manual, and it does say that +/- reactions are calculated into the score, although they do not count for the titer, since it is the last tube to show a 1+ reaction. I still think the results are a little high, but I am satisfied with the explanation, and would rather them perform it than me. Surprisingly, I have not had any questions from the physicians about the results, so maybe they are better informed than I was about this score, or maybe they are simply ignoring it. Thanks everyone for all your help.

[Malcolm Needs ☆]

I have not had any questions from the physicians about the results, so maybe they are better informed than I was about this score, or maybe they are simply ignoring it.

My vote goes for the latter explanation!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[BankerGirl]

My vote goes for the latter explanation!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

That is my theory also, but I thought I would give them the benefit of the doubt.

[Dr. Pepper]

I concur with the second theory. And is any else besides me annoyed when physicians order "lyme titers", "giardia titers", "hepatitis titers" etc on any number of qualitative tests that we do? Aside from prenatal antibodies and ANAs, there aren't too many other things these days we actually titer. So I think that not many doctors know what a titer actually is, let alone interpret one.

I caught my daughter, a budding pediatrician, misusing the titer word, and corrected her. I asked her if she wanted to be just another dumba*s doctor who was the laughingstock of the laboratory. She have me a crude response. That ChristmasI gave her Blood Transfusion Therapy: A Physician's Handbook and the Circular of Information in her stocking.

[carolyn swickard]

"But the score is measured out all the way to the endpoint. If this patient had 1+ on tube one, but weak reactions out to the 1:8 dilution, it would give you a score of 13 (5+2+2+2+2)." Quote

This score makes some sense for the old "HTLA"s antibodies - they would go out quite a way, but be weak the whole time. Was that the antibody detected and titered?

[Mabel Adams]

I want to resurrect this thread again because I want to know how many US labs are turning out scores with their prenatal titers.

There are actually two titration procedures in the Methods section of the AABB Tech Manual. The one in Methods Section 3 'Antibody Detection and Identification' includes a score. In Methods section 5 'Hemolytic Disease of the Fetus and Newborn' the titer procedure does not include calculating a score. I had given it up at a prior workplace but we still do it here. Does anyone know if the OBs or perinatologists have any idea what to do with a score result on a titer?

I was going to try a poll on this but maybe you can do that only when you start a thread? I might have to go to polls and create one.

[carolyn swickard]

Just the titer, no score, using the CAP standardized method (except we incubate for 1 hr, not 30 mins).

[L106]

We do the same as cswickard (except we inculbate for 30 minutes, not 1 hour.)

Donna

[David Saikin]

I "score" if only for personal evaluation of subsequent titers . . . not sure if the docs understand it.