We've had a client express a major concern that a patient's antibody screen was "negative" 6 days after receiving an RhIg injection. From everything that I've ever heard or read there is no correlation between a "positive" or "negative" screen and the effectiveness of RhIg. I was curious as to whether anyone has a policy addressing this. Thanks!

Since RhIg is given IM, it may take several days for the titer in the patient's specimen to be detectable in antibody screens. My experience is that it would probably usually be detectable by 6 days, but it all depends on the patient's body type and how fast she absorbs the RhIg. To my knowldege it is never recommended to test for the efficacy of the RhIg adminstration by antibody screening and/or titers. Any particular reason why an antibody screen was performed at 6 days?

Is there a possibility that the follow-up sample was not drawn from the correct patient, or the shot was given to the wrong person, or the shot was charted as given, but really not?

If the lady was very large, the RhIg may have been given IF, rather than IM, which would also hinder the absorbtion rate.

When we did antibody screens using a tube method, we rarely picked up RhIg. Now that we use Ortho gel, we almost always see a positive screen from RhIg so it may be the method that you are using.

Just a thought!

I'm curious, why was an antibody screen performed 6 days after the RhIG injection?

Thanks for the responses. To answer a few questions.

1. I'm under the impression that this particular client orders these antibody screens one week post-RhIg routinely to determine whether the product is effective. They have been advised that this is not an acceptable practice but whether they will change that is open to question.

2. There is always an outside chance that the specimen was mislabeled and not from this patient but we have requested a redraw.

3. The original "negative" antibody screen was performed by a solid-phase method and there is no sample available for retesting.

As was mentioned there are numerous variables involved which determine whether anti-D will be detected post-injection. I'll fill every one in once we test the redraw. Thanks again!