I am working as a physician at Ankara University Serpil Akdag Blood Bank, Ankara/Turkey.

We are performing antibody screening test for our Gynecology and Obstetrics Departement by gel system (DiaMed).

We observe anti-D positivie result at D negative pregnants who received Rhogam as a prophylaxis and has D positive partner. When we make the titration we do not receive any positive result even we use the same serum sample, gel system.

We have this results only passivly immunized patients.

We would like to have an explanation to this condition.

Thanks

Dr. N. Nuri Solaz (nsolaz@yahoo.com)

What is the initial strength of reaction, and at what titer does the reaction weaken/go away? Not sure I can help..........but maybe I can give you our results.

I see absolutely no value in doing titrations of Anti-D when the patient is known to have received Rh immune globulin (RhoGam). What is the purpose for doing such titrations?

The AABB Technical Manual indicates that circulating RhIg rarely reaches a titer above 4. And, as you know, the amount of antibody present is constantly declining since it is not being produced by the patient. So, very low titers would be expected.

As an aside, the Technical Manual also indicates that doing titers on gel is not recommended because of a lack of data showing correlation between gel and standard tube methods.

The only value I can think of is if your result is >16 you can be fairly certain that it is not the result of a RhIG injection.

I see absolutely no value in doing titrations of Anti-D when the patient is known to have received Rh immune globulin (RhoGam). What is the purpose for doing such titrations?

The AABB Technical Manual indicates that circulating RhIg rarely reaches a titer above 4. And, as you know, the amount of antibody present is constantly declining since it is not being produced by the patient. So, very low titers would be expected.

As an aside, the Technical Manual also indicates that doing titers on gel is not recommended because of a lack of data showing correlation between gel and standard tube methods.

I see your point in relation to reactivity of less than 1+. But I think any reactivity of 1+ or more should indicate a titer regardless of RhIg administration. Otherwise you have no baseline for comparison. If the patient's initial post-RhIg titer is 1 and a month later is 8, there's a very good chance you're dealing with an RhIg failure.

As far as gel titration is concerned we've experienced at least a couple of disgruntled physicians who have complained about significantly higher titer reports from hospitals using gel titration vs. our tube test. Of course the reference lab winds up as the bad guys. It's unfortunate that there isn't much more standardization between different facilities with the titration procedure. If everyone stuck to the AABB protocol life would be much easier.