Backup method for solid phase (Capture-R)

[Clarest]

Hi all,

 

We're moving to our new site in less than half a year. Along with our move, we're going to start with a new NEO instrument. At the same time, we're going to get rid of the manual gel testing system. Currently, we use Galileo, manual capture-R station and gel system. Either Galileo or manual capture-R is our primary testing method (for antibody screen and the first panel), and gel is our backup method which is mainly used for selected cells and repeating antibody screen/panel. Especially, when all solid phase (capture-R) screening cells and panel cells are positive with a negative DAT result, we repeat the antibody screen/panel by manual gel method and if the result is negative, we suspect the reaction could be caused by solid-phase dependent antibody and conclude that "all common clinically significant antibody ruled out" with the use of saline IAT crossmatch when transfusion is required.

Right now, we're looking for a new backup method after phasing out the gel system. Options for us are tube saline IAT, tube LISS and tube PEG. Tube PEG method had been tried before my time and I was told that it's difficult to interpret the result for generalists not blood bankers. However, I heard that tube PEG has the closest sensitivity to solid phase (Capture-R) in the above tube methods. I was asked to do some survey or research on what other labs use as a backup method for solid phase (Capture-R) and what the pros and cons are based on their experience.

 

Please, please give me your inputs. Thank you in advance.

 

Clarest 

[Liz0316]

You must be a large hospital, getting the NEO, so I'm guessing you need one specific method for everyone to follow. I'm from a much smaller hospital and I'm involved in work ups especially the ones that are inconclusive or troublesome.

I like to keep my options open on these work ups. We stock, PEG, LISS and also have a method for a saline 4-drop IAT.

Depending on the patient's history and how they are presenting currently, I would use different medium.

I wouldn't use PEG on a patient with a WAA - why go looking for it? Or for that matter, on a patient with a cold reacting antibody. Once the antibodies are identified (or lack thereof of a clinically significant antibody) I don't want to use a method that I know will enhance insignificant reactivity for the crossmatch.

Of course, if the patient presents again, we start all over again!

Liz

[AMcCord]

We use tube/PeG for our primary backup method, with N-Hance available for those annoying warm/cold autos that are reactive with PeG. I'm the only full timer in Blood Bank - everyone else is a generalist. Some of the generalists on days don't do a lot of Blood Bank. Yes, PeG can be a little more tricky to use (Is it positive or is it a PeG cloud?), but with training and a little experience, your staff will become comfortable with the results they see. I don't consider it a major problem. Of course it helps that our Echo is almost never down (knock on wood!).

[David Saikin]

We use Peg/Tube as b/u for gel. 

[goodchild]

We have ProVue as primary and manual gel as backup. We also have LISS/PEG available for tube testing to have a different perspective when necessary.

[kate murphy]

We have a Galileo, in process of moving to Neo, and a Bio Rad Tango.

We use PEG as our backup method.  We do have LISS for those pesky WAA and colds.

[Clarest]

It sounds like tube PEG is not good for warm auto and colds. However, if tube LISS is used as a backup method for solid phase (Capture-R),  the difference of sensitivity is bigger than that betwen tube PEG and solid phase. What could be the cons for this combo comparing with tube LISS and solid phase? Could you please let me know your experience? Much appreciated.

[AMcCord]

Warm and cold autos also love PeG. Sometimes N-Hance is the only way to get under the auto to see if there is an alloantibody lurking under the auto. Sometimes a saline AHG (no enhancement - longer incubation) test is the only way under the auto. When you decrease the sensitivity of your method, you risk missing a weakly reactive antibody. However, in the case of a stronger auto, if you don't decrease the sensitivity you won't see potentially lurking alloantibodies. The trick is to use the most sensitive method that the specimen will allow you to use. We start with solid phase, bump down to PeG, then N-hance, and finally saline (no enhancement) if we need that to avoid the auto. If we are getting some negative reactions with PeG, we try to do our ruleouts there if we can, rather than switching immediately to N-Hance.

[Clarest]

Hi AMcCord,

 

What is N-Hance? Is it different from saline IAT(no enhancement)?

 

Thanks.

[AMcCord]

Hi AMcCord,

 

What is N-Hance? Is it different from saline IAT(no enhancement)?

 

Thanks.

 

LISS = N-Hance (it's Immucor's brand name for LISS - sorry)

[tigerlilly415]

I had the same issue with Backup method for solid phase when I came to work for this hospital. They used N-hance (a modified LISS) for all tube reactions. Whenever they had panagglutination they would run a tube N-hance screen. The problem was I couldn't get the correlation to match the Echo's sensitivity. Finally I ordered PeG and ran correlation with all three ( Echo-capture, PeG, N-hance) with 20 known positive antibodies. While the Echo reactions were much stronger, I was able to get all positives to react with PeG( some very weak) while the N-hance I had only a ~50% reaction rate. We would miss over half of all "true" antibody reactions using N-hance. I converted us completely to using PeG only for tube. 

[Clarest]

Thanks to you all for your reply. Since our main testing method is solid phase which is either Galileo (NEO in future) or manual Capture, the backup method will be mainly used for the issue of panagglutination with solid phase (or it says solid phase dependent antibody - SPDA). Moreover,  autoantibodies are not uncommon in our patient population. I would love to have  both tube PeG and LISS, but the reality does not allow us...

[Clarest]

Hi tigerlilly415,

 

When you performed the correlation study with 20 known positive antibodies, did you only do antibody screen or antibody screen and panel? Besides doing this correlation study, when you converted the testing method from tube LISS to tube PeG, did you do any other validation for tube PeG method? If you did, how many samples were used in validation and what was based on to decide the number of samples needed for validation? Thank you for your help.

 

Inputs from other members are also welcomed and appreciated.

[carolyn swickard]

_{Our method here is as A McCord's -}

 

_{If the ECHO solid phase is positive with all 3 cells, we run a Capture R Ready ID (to check for high frequency or multiple ABs) and a Solid phase DAT.  (We want to see what solid phase is trying to tell us 1st, before dropping the sensitivity of the test system.)}

 

_{If that is all positive too, we set up 3 trios in tubes,}

_{1 - in PEG, 1 - in LISS (N-Hance) and 1 - no enhancement media/ 1 hour incubation (saline).}

_{We will do all furthur work and crossmatching in the 1st of these test systems that comes up negative.  If they are all still positive - off it goes to the reference lab.}

 

_{PEG is the best tube enhancement media to back up solid phase testing - it is the only one close to solid phase sensitivity.  But, it can still be sensitive to warms and colds.  You still need to have LISS and 1 hr/no enhancement to see under some of these problems.  If you already have tube testing as one of your formats, it doesn't take much to keep some LISS around too.}

_{With PEG, it is very important to emphasize with all generalist training that you DO NOT read PEG after the 37C incubation - you wash it 1st and read only with IgG.  If you have problems getting them to remeber that - eliminate the 37C read in LISS too and just read everything at coombs phase only.}

 

_{This system works pretty well, we have seen underlying antibodies a few times.  It also saves a lot of shipments to the refence labs.  Good Luck}