Strenght of Anti-D when doing ABO typing

[ChrisH]

Question for you all out there.

With all the different types of doing Rh testing human vs machine, tube vs gel etc. When is a patient really called Rh positive?

I would say Tube testing read by a human is the weakest testing method, do you call all that test positive on IS testing Rh Positive? Or do you say anyone testing 1+ or 2+ and stronger positive?

Would you not say that it is very dependent on what antisera ( IgM, IgM/IgG blend) and what manufacture you are using?

[apfelblosm]

What we do is, anything that is positive at IS or Gel is Rh Positive. If it is negative at IS and it is a donor or a baby, we do a weak D test. Otherwise, the person is Rh Negative. I would say otherwise, it is really up to what the package insert for the reagent(s) you are using says as far as how to interpret anti-D results.

[Mabel Adams]

Don't you wish the terminology, reagents and ability to make anti-D all correlated neatly!

[tbostock]

Now that we are doing blood types on the Tango, we are seeing patients coming up positive for D (even some as strong as 3+) that were previously resulted as Rh Neg (performed previously in tube testing).

When we get an Rh Pos on a patient that was previously Rh Neg, we test it with tube testing (usually negative at immediate spin, but positive with weak D testing). So this could be a weak D, partial D, etc.

My concern is for the new patients that we don't know are negative in tube testing. We are reporting them as Rh Pos from the Tango results (for transfusion purposes, we don't collect donor units). Any ideas from the group on this? If the D result is 2+ or less on the Tango, should I be doing weak D testing in tube on all of these patients and calling them Rh Neg?

[ChrisH]

I asked this question because we had an office call us saying that a patient had previously typed Rh negative and we had typed Positive. 2 Different samples came up positive. We have seen this a few times recently and I know that the Alba anti-D seems a lot stronger then the Ortho we had used previously.

Has there been any recent literature on reporting of Rh results?

[Mabel Adams]

We currently have 2 patients that type around 1+ in tube with Alba anti-D that have made anti-D. Both were tested in the past by other tube reagents and reacted somewhat equivocally but were given Rh pos blood. Of course, some patients that test 4+ with anti-D at IS are also partial D and can make anti-D. We have been erring on the side of caution more in recent years, giving Rh neg blood to patients that don't test over about 2+ at IS with anti-D knowing that some of these will be the quantitative weak Ds thought unable to make anti-D. We don't do weak D tests except on babies, initially Rh neg autologous patients whose auto unit is labeled Rh+ and moms whose fetal screen test is diffusely positive (if we ever get one of the latter).

[Barbarakym]

Any ideas from the group on this? If the D result is 2+ or less on the Tango, should I be doing weak D testing in tube on all of these patients and calling them Rh Neg?

This is our policy. If machine gets 2+ or less positive D, we do Tube testing and take that value. If it is a new patient, 2 techs do the testing.

[Likewine99]

I agree, tube testing read by a human is the weakest testing method. Anyone testing 1+, 2+ positive with tube are called Rh positive.

Using Ortho's gel system, we have found that the anti-D in the gel cards is more sensitive than Ortho's tube anti-D.

Don't forget, if a prenatal specimen was tested at one of the large, high volume labs that do a lot of OP work (won't mention any names here but you get the idea) you may see a patient typed as D negative since they don't usually consider weak D typing as a "reflex" test then when they present to your L&D you may see them be Rh pos.

With no disrespect to those labs, Bld Bk is not one of their specialities and is probably a low percentage of what they do in those types of labs. Mabel has it PEGged (no pun intended), if everything related to D typing and antibodies correlated our jobs would be a little easier.

[apfelblosm]

I agree, tube testing read by a human is the weakest testing method. Anyone testing 1+, 2+ positive with tube are called Rh positive.

Using Ortho's gel system, we have found that the anti-D in the gel cards is more sensitive than Ortho's tube anti-D.

Don't forget, if a prenatal specimen was tested at one of the large, high volume labs that do a lot of OP work (won't mention any names here but you get the idea) you may see a patient typed as D negative since they don't usually consider weak D typing as a "reflex" test then when they present to your L&D you may see them be Rh pos.

With no disrespect to those labs, Bld Bk is not one of their specialities and is probably a low percentage of what they do in those types of labs. Mabel has it PEGged (no pun intended), if everything related to D typing and antibodies correlated our jobs would be a little easier.

I think you mistake a weak D typing for a necessity. A lot of labs do not perform weak D testing, not because it is not their speciality, but because it is not necessary and not indicated. A lot of hospitals, like my own, do not perform weak D testing on patients unless they are OB, babies, or donors. Otherwise, it we don't care if they are really negative, because we will give them Rh negative and that will be fine even if they are weak D positive. This may cause instrumentation problems down the road if their weak D becomes stronger, but this is the way a lot of hospitals are treating their samples for safety and cost savings.

Jen

[khalidm3]

All reaction less than 2+ by Tango or by tube should be further evaluated for Mix field-two populations due to Rh mismatch transfusion or feto maternal hemorrhage especially when testing the patients. Ignoring this point may lead to wrong interpretation. By Gel Mix Field and weak reactions are clearly differentiated and Mix field in the Gel should be further evaluated. Patient history is important to decide.

[galvania]

As I'm sure I've said elsewhere on a different forum, a lot depends on whether you are testing patients or donors. For donors you need the strongest possible reagents and methods and the tiniest bit of positivity should be interpreted as a positive. For a patient anything that is weak is a variant D - you can^t tell whether it's a D weak or a Partial D. So then the question is, is it important to know? Well that depends on the patient. A young pregnant woman - well, if you have the possibility to do further work, great - if not, then you're safest treating as D-. For a 90 year old man with a fracture - unless he has an anti-D already, I would be quite happy treating as a D+ - as long as he comes up weakly positive with both of the anti-D reagents that I have used to test him. But then again - different places have different guidelines, and it's important that you follow the guidelines in force where you are. But I would never want to use just one anti-D, regardless of the technique I was using. What constitutes a normal positive for your reagent? Well, each reagent should specify in their package inseerts how thexy would expect their reagent to work, so you should follow the instructions to the letter. Quality control in the lab is a must as well