Anti-P1

[Auntie-D]

I think I must have led a sheltered transfusion life as I have only just come across my first Anti-P1. The antibody had been identified historically (1990), but tires have now fallen to undetectable levels.

 

We have had a crossmatch request come in, and although I know we are supposed to select xm compatible units at 37oC, what about if the antibody screen is negative - you have no way of identifying if the units are actually compatible or not.

 

So the question is - just how significant in anti-P1? the literature states that it is possible that it can cause a transfusion reaction but howl ikely is it?

 

The patient in question is a new haematolgy patient on chemotherapy, so is likely to become transfusion dependent. Staff have crossmatched today stating that the units are compatible, but as the antibody screen is negative, we can't actually say this can we?

 

Can someone put my mind at rest?

 

[Malcolm Needs ☆]

There are a few, very unconvincing, papers about anti-P1 being clinically significant, most of which were published many, many years ago, when the probability is that there was another, unspecified and unidentified antibody present that was the actual cause.

 

The ONLY convincing case that I have read was Arndt PA, Garratty G, Marfoe RA, Zeger GD.  An acute haemolytic transfusion reaction caused by an anti-P1 that reacted at 37 degrees C.  Transfusion 1998; 38(4): 373-377.  In my opinion, however, if you read this paper, it points to the hospital not performing their tests to an adequate level (sorry, if anyone on this site was involved), but those performed by the Reference Laboratory detected the anti-P1 with no problem (not surprising when you read the names of the 1st two authors!).

 

In the circumstances you have Auntie-D, I would have no hesitation, and a totally clear conscience, in transfusing cross-match compatible blood (see also Daniels G, Poole J, de Silva M, Callaghan T, MacLennan S, Smith N.  The clinical significance of blood group antibodies.  Transfusion Medicine 2002; 12: 287-295.).

[Auntie-D]

Fab, thanks Malcolm Being trained in cell path I am a sponge to information where possible.

[Sandy L]

In our LIS system we have anti-P1 classifed as not clinically significant. If the patient has anti-P1 in history and has a current negative antibody screen our system would qualify the patient as eligible for electronic crossmatch.  Since moving to Gel for antibody screening in 1996, we almost never detect anti-P1.

[AMcCord]

Funny this conversation came up.

 

On Friday - 20 minutes before I was scheduled to go home of course - I sat down to do a quick blood type recheck on a prenatal specimen. The antibody screen was beautifully negative on the Echo, but the back type was No Type Determined with a smudge of cells in the bottom of the well. Repeated the blood type, another NTD with a smudge of cells. My A1 and A2 cells for the tube back type were 2+, the B cells were 4+.  Front type looked like a type A with strong reactions. Did a quick IS screen - positive. IS antibody ID - perfect anti-P1 reacting 2-3+ strong.  

 

It's obviously not clinically significant since it was non-reactive at AHG, but I'm taking bets on whether or not the OB doc asks for a titer even though I reported it as clinically insignificant. Any takers?

[Malcolm Needs ☆]

Not only not reactive by IAT, but the P1 antigen not expressed well at birth.

 

I would say that the request for the titre is a conservative 100, 000%!!!!!!!!!!!!!!!!!!!!!!!!

[David Saikin]

I would say that the request for the titre is a conservative 100, 000%!!!!!!!!!!!!!!!!!!!!!!!!

 

 

I agree - I've had OB docs ask of "I" negative blood !!!