Cord Blood Direct Coomb's Methodology

[goodchild]

I tried putting a poll in here so I'll see how that works. I'm looking at methodology that people choose to perform their cord blood DATs.

 

Originally we used tubes.

Switched to manual gel ~2003.

Switched to ProVue ~2011.

 

We've run into several instances where ProVue/manual gel are negative, physician calls us and asks us to check into it and we run the DAT in tubes and get 1+ reactions.

 

We've run into several instances where ProVue is positive but manual gel is negative.

 

I've considered establishing an algorithm where if the mom/baby are ABO incompatible you'd use tube testing for the DAT otherwise you'd use gel. Is this overcomplicating a simple test?

 

As a note, we only run cord evals on Rh-neg women, in the presence of antibodies, or physician's request. Runs between 40-100/month.

[tbostock]

We do our cord blood DATs on the Tango (solid phase). We found it to be a little more sensitive than tube testing.

[R1R2]

How was your validation of DATs on the ProVue.  Did you note any discrepancies?  I would stick with one method for all. 

[jalomahe]

We do our cord bloods DATs by on the Immucor Galileo (Capture solid-phase). We are switching to Immucor Echos (Capture solid phase also) in the next month or so and will move them to Echos at that time.

 

This might be a silly question but what reagent you using for your tube methodology, anti AHG or anti IgG. I only ask because it was an issue here at the beginning because the Galileo DAT is an IgG method and the techs would occassionally, mistakenly use anti AHG in the tube and end up having a discrepancy in the results. We have since corrected this issue and now our results correlate quite well.

Edited August 15, 2013 by JALOMAHE

[snydercl]

We use the Echo for DAT's.  We however have a policy that we must recheck all positive DAT's with manual gel. 

[Lbiggs]

We just had a situation with a positive DAT on cord blood. Baby A pos and Mom A pos. I called our reference lab to see how they would work that up and they suggested that all positives on cord be retested with heal stick or venous blood first. We retested on heal stick, baby was still DAT pos. Mom has neg antibody screen. Mom most likely is creating antibody against low incident antigen that we don't have on our screening cells per our reference lab. Mom's, natural dad's and baby's blood along with ethnicity of both parents had to be sent to reference lab for work up for future pregnancies.

[goodchild]

How was your validation of DATs on the ProVue.  Did you note any discrepancies?  I would stick with one method for all. 

 

This is one of the reasons I'm re-examining this process. The validation for the ProVue was done before I came on as quality assurance. The validation plan didn't mention cord blood testing or direct antiglobulin testing at all. There were some specimens tested and results available in a spreadsheet. The results showed some discrepancy between the ProVue and manual gel:

The manual gel procedure instructed technologists to wash the cells one time prior to performing type/Coomb's. We found several instances where ProVue was positive and washed/unwashed manual method was negative by multiple techs. There were also instances where ProVue was positive and unwashed manual gel was positive but washed manual gel was negative by multiple techs.

Taking into account we didn't have a sufficient validation for running cords on ProVue, the fact that we can't transmit DATs via the interface with Meditech 5.65, the fact that microclots in the cord specimens have put us into ProVue downtimes (not so much recently, but has happened multiple times) and several other reasons we decided to stop using ProVue for now.

 

We do our cord bloods DATs by on the Immucor Galileo (Capture solid-phase). We are switching to Immucor Echos (Capture solid phase also) in the next month or so and will move them to Echos at that time.

 

This might be a silly question but what reagent you using for your tube methodology, anti AHG or anti IgG. I only ask because it was an issue here at the beginning because the Galileo DAT is an IgG method and the techs would occassionally, mistakenly use anti AHG in the tube and end up having a discrepancy in the results. We have since corrected this issue and now our results correlate quite well.

mono anti-IgG

[rravkin@aol.com]

_{Goodchild, it has been my experience that although Gel testing of Cord DAT, manually or automated, is very work-flow friendly it is not more sensitive than the microscope which can readily be used to confirm negative or positive DAT's. I know that I may have just said a bad word, microscope, and I  empathize, but it is still more sensitive than Gel and equally as user friendly, but not so work-flow friendly; and the only way to get to it is to use the tube method. So if you are having problems with gel, tube is the best way to go, at least for the Cord DAT.}

[carolyn swickard]

How do you get around the frequently clotted EDTA specimens when doing cord bloods on the ECHO?  Do you wash the specimens before putting some cells on the instrument?  Otherwise - does the ECHO wash the specimens enough for a valid DAT?  Very curious - what is your method? 

 

We tried our ECHO with cords at first, but just had too many problems with clots.  Went back to tubes for cord bloods.  Thanks for any help and time.

[EDibble]

 This is exactly the history with cords here. Started on the Echo. Even washed specimens gave us falst positives. We do ours in tube now.

How do you get around the frequently clotted EDTA specimens when doing cord bloods on the ECHO?  Do you wash the specimens before putting some cells on the instrument?  Otherwise - does the ECHO wash the specimens enough for a valid DAT?  Very curious - what is your method? 

 

We tried our ECHO with cords at first, but just had too many problems with clots.  Went back to tubes for cord bloods.  Thanks for any help and time.

[Dansket]

...The manual gel procedure instructed technologists to wash the cells one time prior to performing type/Coomb's. We found several instances where ProVue was positive and washed/unwashed manual method was negative by multiple techs. There were also instances where ProVue was positive and unwashed manual gel was positive but washed manual gel was negative by multiple techs...

What were the differences in reactivity comparing automated versus manual gel tests? 

[R1R2]

I tried putting a poll in here so I'll see how that works. I'm looking at methodology that people choose to perform their cord blood DATs.

 

Originally we used tubes.

Switched to manual gel ~2003.

Switched to ProVue ~2011.

 

We've run into several instances where ProVue/manual gel are negative, physician calls us and asks us to check into it and we run the DAT in tubes and get 1+ reactions.

 

We've run into several instances where ProVue is positive but manual gel is negative.

 

I've considered establishing an algorithm where if the mom/baby are ABO incompatible you'd use tube testing for the DAT otherwise you'd use gel. Is this overcomplicating a simple test?

 

As a note, we only run cord evals on Rh-neg women, in the presence of antibodies, or physician's request. Runs between 40-100/month.

How long had the cord sat before you repeated the DAT in tube?  did you also repeat it in gel?   Like I said before, I would stick with one method.  Did the MD do anything different in respect to treatment based on the repeat positive DAT?

 

I also had difficulty correlating DATs on ProVue with manual gel,  The discrepancies involved  1+ positive with ProVue and negative with manual gel.  I did not investigate further so I do not do DATs on ProVue.  

[goodchild]

What were the differences in reactivity comparing automated versus manual gel tests? 

 

The only results identified were 0, 1+, 2+. Aside from the pos/neg discrepancies, all reactivities were the same.

 

How long had the cord sat before you repeated the DAT in tube?  did you also repeat it in gel?   Like I said before, I would stick with one method.  Did the MD do anything different in respect to treatment based on the repeat positive DAT?

 

I also had difficulty correlating DATs on ProVue with manual gel,  The discrepancies involved  1+ positive with ProVue and negative with manual gel.  I did not investigate further so I do not do DATs on ProVue.  

Maybe a day or two at most. Tests were repeated by multiple techs in tube/gel and everyone had the same results. I know in these circumstances the MD was confused with a negative Coomb's when going through his differential diagnosis. It's hard to say if anything was changed treatment wise based on the Coomb's reaction or whether it was a "feel good" test - my followup didn't include a discussion with the MD. Thank you for the information regarding your ProVue correlation experience.

 

From this poll I was actually very surprised to see that so many people are still doing tube DATs.

[OxyApos]

Tube DATs are cheap and it gives the generalists practice using the scope more frequently than problem solving time.  I would like to put them on the Echo but clots, turn around time, and cost are the issue.  I can do the tube method in about 5 min rather than the steps to putting them on the Echo.  I also can't batch them...the doctors want them run as we receive them.  If I could batch them, I would put them on the Echo.