Anti-C3d, -C3b testing of infant sample

[yiams]

Blood Bankers,

this question came up in our transfusion service the other day and I did not have a good answer. We normally test our cord blood DAT's with anti-IgG only.

The question: At what age do you begin testing with anti-C3b, -C3d?

[Malcolm Needs ☆]

Blood Bankers,

this question came up in our transfusion service the other day and I did not have a good answer. We normally test our cord blood DAT's with anti-IgG only.

The question: At what age do you begin testing with anti-C3b, -C3d?

I would start from day 1.

I know what the text books say about babies having a poor complement system, and that the DAT is always IgG only, but don't you believe it!

I have seen cord bloods with a positive DAT by IgG and C3d. In each case, I may add, the maternal antibody was related to the Kidd Blood Group System (either anti-Jka or anti-Jkb), but if it can happen with these, then there is the possibility that it can happen with other specificities.

What the clinical significance of this is, is another matter altogether................

:):)

[Yanxia]

I agree with you, Malcolm.

[adiescast]

I would start from day 1.

I know what the text books say about babies having a poor complement system, and that the DAT is always IgG only, but don't you believe it!

I have seen cord bloods with a positive DAT by IgG and C3d. In each case, I may add, the maternal antibody was related to the Kidd Blood Group System (either anti-Jka or anti-Jkb), but if it can happen with these, then there is the possibility that it can happen with other specificities.

What the clinical significance of this is, is another matter altogether................

:):)

So was it the mother's complement that crossed the placenta or did the mother's IgG use the baby's complement to coat the cells? Has anyone ever actually studied this? And, as you say, how significant is it?

I know we only do the IgG for a cord blood DAT. I am sorry to say I never questioned that practice.

[David Saikin]

I agree with Malcolm also . . . I don't believe that complement crosses the placenta.

[Malcolm Needs ☆]

We have not performed a study (indeed, I'm not certain how one could), but I doubt if it is maternal complement on the grounds that we would expect to see it much more frequently involved with any other maternal antibody that is capable of stimulating the complement cascade......but I don't know.

:confused::confused:

[shelleyk482]

We use IgG for cords only. All non-cord samples are tested using a polyspecific reagent.

[Malcolm Needs ☆]

We use IgG for cords only. All non-cord samples are tested using a polyspecific reagent.

I think this is the practice of the huge majority of Blood Banks.

As I said in an earlier post, I don't know of the clinical significance when the cord DAT also shows complement activity, but, certainly in the cases I've seen, there was no clinical haemolytic disease (but there is always a first time - it wasn't that long ago that Gerbich antibodies were thought to be clinically benign as far as HDN was concerned).

:):)

[Townsend]

We perform only IgG DATs on any neonatal patient - that is any patient under 4 months of age. Any patient 4 months and older gets a Poly DAT.

[yiams]

Everyone,

Thank you for the responses to my question. I hope you are all enjoying a Christmas break. A co-worker of mine asked this question. I know Malcolm responded that we should begin testing for complement coating on the day of birth. But is there a general consensus on how old a child should be before we must/should begin testing for complement coating?

Day of Birth is one reply. Is that agreed upon by everyone? A week of age? Two weeks? Three days?

I should mention, too, that we only perform anti-IgG at this time. We do not stock polyspecific AHG. This, in fact, would be our only use for polyspecific and we are not the primary birthing center in town. But perhaps we should begin testing with anti-C3b, -C3d? But would that provide us with any more information for treating the child?

[Malcolm Needs ☆]

Everyone,

Thank you for the responses to my question. I hope you are all enjoying a Christmas break. A co-worker of mine asked this question. I know Malcolm responded that we should begin testing for complement coating on the day of birth. But is there a general consensus on how old a child should be before we must/should begin testing for complement coating?

Day of Birth is one reply. Is that agreed upon by everyone? A week of age? Two weeks? Three days?

I should mention, too, that we only perform anti-IgG at this time. We do not stock polyspecific AHG. This, in fact, would be our only use for polyspecific and we are not the primary birthing center in town. But perhaps we should begin testing with anti-C3b, -C3d? But would that provide us with any more information for treating the child?

I did also say, however, that a positive DAT with IgG and C3d is exceptionally rare, and may not be any more clinically-significant than IgG only, and so I would be comfortable if anti-IgG only was used.

:):)