Gel testing anyone?

[LIMPER55]

Our department will probably never get away from tube testing. Tube is much quicker for our trauma center.

Gel is very good for our routine work.

[Brenda K Hutson]

We use tube testing for our blood types; just use GEL for the Antibody Screen and Antibody Identification (though have LISS and PeG available for Antibody ID when/if needed). I don't think it takes that long to set up an antibody screen in GEL; and it is certainly much easier to read and grade the reactions.

Brenda

Our department will probably never get away from tube testing. Tube is much quicker for our trauma center.

Gel is very good for our routine work.

[Abdulhameed Al-Attas]

Gel testing offers many advantages over traditional methods:

• Improved sensitivity and specificity

• No-wash antiglobulin procedure

• Standardized procedures

• Improved turnaround time

• Enhanced regulatory compliance

And also uses small sample size.

[mrmic]

To sum up in my humble opinion....

There is no perfect system. All enhancements work well as long as they are used in the methods they are designed. Saline vs LISS vs PEG vs Polybrene vs gel (which is just a miniature LISS), vs ?? They will all have their weaknesses which you need to be aware of. A reference lab will likely need to be able to use the majority of them, however, a transfusion service does not. You will need to evaluate the systems based on how it will work for your laboratory with regards to techs' abilities on various shifts, turn-around-times and types of patients you primarily treat. Generally, a tube methodology is used for backup and the ability to refer to a reference lab will save you from having to keep different methodologies for different senerios.

The best system is the system that works the best in your (techs) hands and your record keeping.

wow....that was a breezy soap box....I'll step off now.

good luck

[BBK710]

We use tube testing for our blood types; just use GEL for the Antibody Screen and Antibody Identification (though have LISS and PeG available for Antibody ID when/if needed). I don't think it takes that long to set up an antibody screen in GEL; and it is certainly much easier to read and grade the reactions.

Brenda

We do the same as Brenda. I am in no hurry to do blood types in gel since I have read that there are so many weak D issues with historical types etc. And I agree that it is much faster and in my opinion easier to do the blood type in tubes.

[Kathy]

If you get a positive antibody screen in gel and do it in the tube and it is negative, how do you know which one is right? How do you know when you need to revert to the tube testing when your primary method is gel?

[Malcolm Needs ☆]

Gel testing is very sensitive. tube less so. But, before the invention of column agglutination technology, almost all tests were performed in tubes (even microplates could be thought of as extremely short tubes). There were not hundreds of deaths caused by tube technology - it was just that it was cumbersome and not open to easy automation.

As long as your tube technique is controlled by the use of IgG-coated red cells to ensure adequate washing and non-inhibition of the AHG, the tube technique is safe;so in the scenario of which you write, believe the tube.

[AMcCord]

The best system is the system that works the best in your (techs) hands and your record keeping.

Exactly!

[galvania]

But of course it MIGHT mean that you have an antibody that is present against a low frequency antigen that is present on the screening cells but not on the panel cells

[Kathy]

I spent 19+ years doing tube testing exclusively and am now in a hospital that does gel antibody screening/antibody ID exclusively (although we do have a tube procedure). You are right. We never killed anyone. I am on a learning curve from a management standpoint here, so forgive me if I ask stupid questions.

Edited July 21, 2011 by Kathy

[tbostock]

I spent 19+ years doing tube testing exclusively and am now in a hospital that does gel antibody screening/antibody ID exclusively (although we do have a tube procedure). You are right. We never killed anyone. I am on a learning curve from a management standpoint here, so forgive me if I ask stupid questions.

There is no such thing as a stupid question on BBT...we're all here to learn from each other.

[Deny Morlino]

Well said Terri!!

[L106]

Stupid questions are OK.......sometimes some of us give a stupid answer!! Well, that is rarely true. There seems to be a lot of top-notch Blood Bankers on this site!

[Brenda K Hutson]

Depends on "why" it was positive in GEL. Once you use it for awhile, you get a "feel" for what may appear to be due to rouleaux or a cold agglutinin. You can then confirm (or rule out) those with further tube testing. If those are interfering, you could use tube for that patient. Same for warm autos (if upon further testing for example, you clearly identify it is a warm auto; and it is weak enough to be negative in LISS; then you can use LISS for that patient).

Sometimes we get scratchy reactions in the GEL Antibody Screen; then obtain a Negative GEL Panel. Just have to be careful when deciding whether it was just junk in the screen, vs. a Low Incidence.

So it will become a combination of learning what reactions to be suspicious of in GEL, and having your own Institutional SOPs as far as approach to work-up and changes in potentiating media used. And that will result in > 1 possible approach.

Not sure that all came out as intended....sorry.

Brenda Hutson

If you get a positive antibody screen in gel and do it in the tube and it is negative, how do you know which one is right? How do you know when you need to revert to the tube testing when your primary method is gel?

[jlemmons]

One time in our lab our ProVue was having problems and we were waiting for service and so were using the manual gel workstation and the belt broke on the manual gel centrifuge. We all looked at each other in horror and said" We have to go back to tube for everything now?" Luckily our Ortho person had a demo centrifuge he could loan us until we got the belt in. It was a very interesting thought process after so many years of using gel.

[SMILLER]

I agree about the time saving aspect, less hands-on but still takes about 1/2 hour to complete a screen. A few non-specific cold specimens may cause you to repeat in tube. Other than that, the results are very consistant and easy to read once your techs get over the learning curve.

We found that once our techs grew more comfortable with reading iffy gels, we go less and less to a tube screen for confirmation.

Also note that since a gel XM is only the AHG phase, you will also still have to do an IS in tube for crossmatches.

[Kathy]

I work in a lab where we very infrequently encounter antibodies - maybe one or two per month. Some of our techs are not very good with antibody identification and problem solving when the antibody is not clear-cut. We don't have a SOP for when we would revert to the tube method, nor do we have a saline replacement technique in our procedure manual. I would like add the saline replacement to our procedure manual, and, since it means that we would be using the less sensitive method (tube) instead of the more sensitive method (gel), my medical director is appropriately questioning me how I know for sure that we wouldn't be missing clinically significant antibodies. He also wants to know how I would validate the saline replacement technique. I would would really hate to send a specimen with rouleaux to the reference laboratory, so I would like to give him some sort of concrete answer.

[Desoki]

Be carful of storage of gel cards also even with using gel you can not dispense tube, gel will minis and facilitate your work but still need tube in some cases especially in Ab identified because sometimes need steps of IAT.

[Mabel Adams]

Gel won't pick up weak rouleaux but it will give false positives with really strong rouleaux and there is no way to fix it except to do tube testing. Also, what we call "gel junk" (usually antibodies to the antibiotics in the gel diluent--made worse by improper storage) must be resolved by tube. You can also run into problems with warm autos and cold antibodies as described above. Anti-M's come up really nicely in gel--often showing dosage. You almost never find a Lewis antibody in gel. Small hospitals that choose to have no backup method must realize that they will not be able to do AHG xms at all for patients with the above problems that require AHG xms. You may need a policy for defining these things as clinically insignificant so IS xm is allowed but that doesn't work if the patient has an anti-K also.

Many reference labs are loathe to do gel and don't really trust it. You may find that you can't send out problems because your reference lab won't find the reactions in tube. There are real antibodies that react in gel and not tube so they aren't always completely right to rely only on tube.

Remember there are new instruments/vendors entering the US market in 2012 due to Ortho's patent rights expiration. Bio Rad will be able to market the European gel system in the US and Ortho is rolling out an improved automated instrument. I saw a European vendor at the AABB meeting with gel cards with 8 tubules instead of 6. There may be some new ways to skin this cat after next year.

[Mabel Adams]

And gel is even better than tube for picking up passive anti-D from RhIG so if you haven't given up doing antibody screens with post-natal RhIG workups you will want to.

It also seems to me that it often picks up anti-E in the homozygous cells but not the heterozygous cells. If the screen is consistent with anti-E and reacts < 2+ you can save time by adding another R2R2 (EE) cell to the first panel so you have 3 positive reactions with E pos cells and won't have to run another EE cell in another run later. Or you can incubate the panel for 30-40 min (per your validation of these times) to enhance the weak reaction. Or you can accept 2 pos and 5 negatives rather than the rule of 3. But many of us want to see 3 E pos cells react before we call it anti-E.

[Auntie-D]

In the UK the primary mode is gel. I'm finding it a bit weird following this thread - I've been qualified 12 years and have never used anything other than gel for primary identification. The only problem I have found it that Ortho doesn't seem to pick up anti-Cw (but who cares ). Diamed (BioRad) seems much more sensitive all around. We can send IDs away to our reference lab (who use Ortho) and what we scored as a 2/3 will come back as 0.5! There have been 4 occasions in 2 years that we have identified an antibody with Diamed and Ortho hasn't picked it up. And we only do about 30 groups a week!

[BrianD]

this discussion is very interesting and helpful. we use SPRCA for everything (ABO/Rh, AbScr., AbID, Ag typing, DAT,Weak D, and IAT-XM). occassionally, we find 'false positive' AbScr's due to something reacting to the plate....nothing comes up in tube testing or at our IRL so we've just purchased a ProVue and have started our sensitivity comparisons between the SPRCA method and the CAT method....our intention is to use the CAT to "confirm or deny" these plate-dependant "maybe-abs" because in our experience, the solid phase is so much more sensitive than the tube testing (what is +/- in PEG/tube comes up 3+ in the solid phase system) that we feel very uncomfortable in using tube testing to identify a 'false pos' from the solid phase system.

nb: a downside to these methods so much more sensitive than tube screening is a good portion of what we are identifying are very weak WAABs, HTLAs, or things that do not truly present a transfusion challenge.

[Malcolm Needs ☆]

nb: a downside to these methods so much more sensitive than tube screening is a good portion of what we are identifying are very weak WAABs, HTLAs, or things that do not truly present a transfusion challenge.

Absolutely. As I've said on this site more than once, I cannot recall patient's falling over dead in huge numbers as a result of transfusion reactions in the days when all tests were performed by tube technique.

The modern technology is undoubtedly much more sensitive, but, what we must also remember is that not all antibodies are clinically significant (whatever the specificity) and that, sometimes, I feel we are speding hours working on really, really weak antibodies to get the specificity, and then spending a long time finding antigen negative blood to transfuse when the chances are extremely high that antigen untested, cross-match compatible blood will cause no clinical sequalae, and the patient will probably never present again anyway, even if the antibody titre is boosted.

:paranoid::paranoid:

[Mabel Adams]

Auntie-D, do you get a lot of false positives due to the increased sensitivity of the Diamed gel over Ortho? Also, do you find many antibodies to the gel diluent? (I assume you use commercially made pre-diluted cells so there are antibiotics and whatnot in your tests.)

[Malcolm Needs ☆]

Auntie-D, do you get a lot of false positives due to the increased sensitivity of the Diamed gel over Ortho? Also, do you find many antibodies to the gel diluent? (I assume you use commercially made pre-diluted cells so there are antibiotics and whatnot in your tests.)

Hi Mable,

In my own experience at the Reference Laboratory, it is just the opposite. We get far more samples sent in from Ortho users in which we cannot detect (usually) any antibodies than we do from DiaMed users, and, even when we send on the sample to one of our own Reference Laboratories that uses Ortho technology, and they detect something, I cannot recall any occasion when the antibody has been anything but "weak auto-rubbish".

We get one, maybe two, samples a year in which we detect antibodies to the diluent, and these are not a problem, as we just change the diluent from Alsever's to Dil-2, and the probelm disappears.