Due to a recent event, I am looking to develope a protocol for determining the neccessary steps to take when deciding that an initial positive antibody screen is actually a negative antibody screen. Preface to say that I am using a LISS tube technique.

Presently, once we get a positive antibody screen result we perform an antibody ID. If this is negative we either perform the antibody screen again with PeG or use another lot number of screening cells. If either is negative we interpret the initial antibody screen as negative and modify the result. This modification is reported to the MD or nurse in charge of patient.

As we do not have a written SOP for this, other than positive antibody screens require an antibody ID be performed. it requries that I develop a new procedure for all staff to use in this instance, similiar to what we do for ABO dscrepancies. I also need this SOP so that a staff member know that simply repeating the same antibody screen one additional time and getting a negative does not overrule the initial positive result.

I also know at other facilities I have worked at , another method would be to simply ask for a new specimen and perform testing on that specimen if the reactions were atypical of a true positive reaction.

If anyone would be willing to share there thoughts or even an SOP :-) I would appreciate it.

I am trying to get my capital budget approved for automation, but with the economy the way it is.....

Boy, this is a difficult one!

If the screen is positive the first time around as 1+, or maybe even 2+, but is negative again using the same cell at least twice more by the same technique, then I would be happy that the original findings was an error, but otherwise no.

I certainly wouldn't be happy if the screen were positive, but two panels were negative, unless the positive screening cell was included. It may be that the screening cell is positive for an antigen not represented on any of the panel cells, and that the antibody is genuine.

Do you perform your tube technique by pre-warming the reactants prior to mixing? If not, it could be worthwhile pre-warming one set and performing the same panels at room temperature (but, again, I would always include the positive screening cell).

It could also be worthwhile trying a NISS tube technique, in parallel with the LISS tube technique, with, of course, an appropriately longer incubation time, just in case the antibody is "LISS only".

These are only initial musings, whilst I'm waiting for my young son to get ready for bed. I'll think about it more tomorrow!

:eek::eek:

When the initial ABS is positive and your panel, using the same technique, is negative, I think that using the alternative techniques such as PEG and Pre-Warm are worth while; but our ultimate goal is providing compatible blood products. I would not disregard any results if they are inconclusive and proceed with extended crossmatch for compatible units using the same technique for which the initial positive react was obtained. If compatible donor cells are acquired then we have acheived our goal. When futher testing is performed on new patient specimens after three or more days we wil then see if the positive result initially aquired will persist. If compatable units are not obtained then we should send out specimens to a reference lab for a complete workup.

As far as weather to change an initial positive ABS result I would not only because you would want to maintain the record for future issues if any. If this initial positive was indeed a technical error it will work it's way out over time.

As far as the response of Croydon I would be agreeable if the post testing were performed by different staff. Therefore, if the result was do to technical error you would have a better ability to find out the exact problem if any.

Very good point!

:):)

With a positive screen and a negative panel, we will repeat the original positive screen by the same method to see if it is reproducable. If the same screen by the same method (preferably by the same tech) is negative, we call it negative. The only time I might be concerned about this is if the initial result was very weak. If it was a good strong result and indicative of an actual antibody, I would expect it to repeat under the same conditions. I do not have this codified in procedure. Automation may not help you with this issue. There are times when you can get a positive result on the instrument that never repeats no matter how many times you run it (OK, I only tried it 4 times with a couple of samples...) Stranger things have happened.

The initial test result was a microscopic positive result. The tech questioned the initial pos result and performed a repeat screen one time and saw a negative result. The tech never recorded his initial pos results. Needless to say, if the tech followed SOP and performed an AB ID, a weak clinically significant antibody would have been identified.

It is the norm to repeat any initial test result in duplicate, as one can not say one repeat test over rules the initial test result. I would always err to the initial positive result and perform an antibody ID and if negative repeat testing using either a different methodology (PeG) or a different lot number of reagent antibody screen, before I interpreted antibody screen result as a negative result. In the above case, performing pre-warm technique is not advised, as weak antibodies are often eluted resulting in a false negative.

I would of course not discount a strong positive result if it was reproducible, even in the event of negative antibody ID panels as I am aware of the possibility of a low frequency antibody occuring, especially with having 72 different nationalities of patients that come to our facilitiy. We are indeed a melting pot here.

In any case, it is incumbent on myself to give the tools/direction to my staff for resolving this or similiar antibody screening issues, so each one of my staff can take the same steps. I can always state in the SOP that when in doubt always perform a AHG crossmatch and enter this as an instruction in the patient's historical file/ patient problem area. Of couurse all the additional work (repeat antibody screen; PeG antibody screen, antibody panel) would be resulted and documented, as well as any change in final interpretation documented in the computer record/patient record and whom was notified of the change.

In at least one of his three editions of his book Appkied Blood Group Serology, Peter Issitt wrote that microscopes should be banned from a Blood Transfusion Laboratory.

I agree with him 100%.

:):)

In at least one of his three editions of his book Appkied Blood Group Serology, Peter Issitt wrote that microscopes should be banned from a Blood Transfusion Laboratory.

I agree with him 100%.

:):)

Unfortunately, for this particular case, the antibody was clinically significant, although very weak, and caused a transfusion reaction and as we all know, the in-vitro strength of reactivity does not always indicate the in-vivo effects of a given antibody.

Edited February 16, 201015 yr by conwaysbb

Unfortunately, for this particular case, the antibody was clinically significant, although very weak, and caused a transfusion reaction and as we all know, the in-vitro strength of reactivity does not always indicate the in-vivo effects of a given antibody.

I would totally agree with what you say in the last part of this post. One only has to think of the number of anamnestic responses to a weak anti-Jka in the literature.

What kind of reaction was it? Was it a full-blown acute transfusion reaction with rigors, dark/black urine, etc, a lower rise in Hb than would be expected, or what?

I ask out of interest, rather than trying to catch you out (in case it reads like that).

:confused::confused:

Without the microscope in the BB how are we going to result FMH screen and KB for that matter? I know that we can find nusence artifacts and ratal our brians with justification. But which is the lesser of two evels a false negative or the microscope? Its not easy!

Without the microscope in the BB how are we going to result FMH screen and KB for that matter? I know that we can find nusence artifacts and ratal our brians with justification. But which is the lesser of two evels a false negative or the microscope? Its not easy!

Well yes, obviously for tests like an FMH and a KB, but I (and I think Peter Issitt) was talking about a serological test.

:)

In this case here apparently the microscope was a pertainent device in the detection of this very weak reaction which apparently lead to a transfusion reaction (well not directly) the details of which we have yet to see. I wonder why the PeG repeat did not bring about a macroscopic positive result?

I would totally agree with what you say in the last part of this post. One only has to think of the number of anamnestic responses to a weak anti-Jka in the literature.

What kind of reaction was it? Was it a full-blown acute transfusion reaction with rigors, dark/black urine, etc, a lower rise in Hb than would be expected, or what?

I ask out of interest, rather than trying to catch you out (in case it reads like that).

:confused::confused:

Thankfully there were no signs of intravascular/extravascular hemolysis or hematuria, but did include pos DAT, other symptoms. The HGb bump was less than expected and HGB later decreased, but whether it was due to the transfusion or the disease state is in question. Of course the patient was kept additional days to monitor with loss of revenue and increased nursing care required. The patient did not receive the quality of care that is expected. Plus all the paperwork involved including regulatory notifications.

In this case here apparently the microscope was a pertainent device in the detection of this very weak reaction which apparently lead to a transfusion reaction (well not directly) the details of which we have yet to see. I wonder why the PeG repeat did not bring about a macroscopic positive result?

Actually when we worked it up the PeG did enhance the reaction as part of the transfusion reaction process.

That is why one of the options that is being discussed would use another method to repeat antibody screen as part of the resolving a possible false positive.

Due to a recent event, I am looking to develope a protocol for determining the neccessary steps to take when deciding that an initial positive antibody screen is actually a negative antibody screen. Preface to say that I am using a LISS tube technique.

Presently, once we get a positive antibody screen result we perform an antibody ID. If this is negative we either perform the antibody screen again with PeG or use another lot number of screening cells. If either is negative we interpret the initial antibody screen as negative and modify the result. This modification is reported to the MD or nurse in charge of patient.

As we do not have a written SOP for this, other than positive antibody screens require an antibody ID be performed. it requries that I develop a new procedure for all staff to use in this instance, similiar to what we do for ABO dscrepancies. I also need this SOP so that a staff member know that simply repeating the same antibody screen one additional time and getting a negative does not overrule the initial positive result.

I also know at other facilities I have worked at , another method would be to simply ask for a new specimen and perform testing on that specimen if the reactions were atypical of a true positive reaction.

If anyone would be willing to share there thoughts or even an SOP :-) I would appreciate it.

I am trying to get my capital budget approved for automation, but with the economy the way it is.....

If you are using the same cells with PeG, you "might" be able to justify channging the record from POS to NEG.

However, I would not recommend doing that just because another Lot# is negative. You may have an antibody to a Low Incidence Antigen that is not present on the 2nd set of screening cells. And while you may not screen units for a Low, you would probably want to perform a AHG XM (vs. Immediate Spin).

Brenda Hutson

Of course we will need microscopes for FMH screens and Fetal Hemoglobin tests. I'm sure Malcolm (& Issitt) are refering to typical BB testing procedures.

I personally think "to microscope" or to "not microscope" depends on the facility. I'm sure Malcolm does fine without one. I would prefer to stop using a microscope, and some of my staff would probably do fine without them. However, I am sensitive to the fact that some of our rotating staff (who may only be scheduled in BB for a couple days every few weeks) need that security of the microscope to feel confident in their results.

Unfortunately, the techs do occassionally find microscopically positive "trash" that wastes their time. But if it lets them sleep better at night knowing that they haven't missed something, I don't mind scanning my tubes under the scope for a couple seconds.

Edited February 16, 201015 yr by L106

I've pretty much been able to get my staff to quit leaning on the microscope to read their antibody screens and panels. Most of our work is solid phase now anyway and that helps. I had one staff member who was nervous about it and we went through a training process. She was able to stop using the microscope after about a month and felt very good about her readings.

I have worked with people in the past who would actually shake the Dickens out of their tubes and then look under the microscope to make sure they didn't miss anything.

This message is a repeat of the response to ConwaySBB I made ealier today. I was understanding the problem as being able to reverse an initial positve ABSC to negative and what might be involved. I was wondering if the same statistical annalysis could be applied to this situation as when we bring in a new non-historic Ab. To bring in a new Ab we need three positive cells and, of course, rule out everything else. I am not sure if statistically this is the same situation nor am I sure I would overturn an initial positve ABSC even if we could, at least statistically.

Thankfully there were no signs of intravascular/extravascular hemolysis or hematuria, but did include pos DAT, other symptoms. The HGb bump was less than expected and HGB later decreased, but whether it was due to the transfusion or the disease state is in question. Of course the patient was kept additional days to monitor with loss of revenue and increased nursing care required. The patient did not receive the quality of care that is expected. Plus all the paperwork involved including regulatory notifications.

Thanks conwaysbb.

I think that it is vitally important in such a case to differentiate between a delayed haemolytic transfusion reaction causing a less than expected increase in haemoglobin and other possible causes, such as your patient's disease state.

A positive DAT alone after a transfusion, even if the DAT were negative prior to the transfusion, is not diagnostic of a delayed haemolytic transfusion reaction. Nor is a positive DAT and a less than expected rise in haemoglobin. The former could just be what George Garratty terms a delayed serological reaction (where tests such as the DAT become positive, but there are no clinical sequelae for the patient). The latter may be a combination of this and a less than expected rise in haemoglobin due to the patient's disease state.

If it were the latter, then you would still need to keep the patient in for a longer period, and perform all the extra tests, but it might well prove that the transfusion was coincidental, rather than causitive.

:confused::confused:

Did I miss something somewhere that actually gave the specificity of the antibody? Did you then do an eluate on the positive DAT to see if it was also positive with the original screening cell?

Boy, this is a difficult one!

It could also be worthwhile trying a NISS tube technique, in parallel with the LISS tube technique, with, of course, an appropriately longer incubation time, just in case the antibody is "LISS only.

:eek::eek:

YOU HAVE ME AGAIN MALCOLM. What is "NISS"?

I have worked with people in the past who would actually shake the Dickens out of their tubes and then look under the microscope to make sure they didn't miss anything.

So, it's not just me then. Back when we were still doing tube testing, I once worked with a couple people who would say, "So your result is positive? Just shake the tubes harder, you can usually get rid of it!" :eek:

I was a junior member of this particular staff and I was not very popular with them as I would just REFUSE. RIDICULOUS!!!!

YOU HAVE ME AGAIN MALCOLM. What is "NISS"?

Ah, this one is an easy one. It's just a bit of UK jargon!

NISS is normal ionic strength saline.

LISS is low ionic strength solution.

By the way, I entirely agree with the feelings that you posted after this. I think that you were very brave, but absolutely right.

:D:D:D:D

NISS is normal ionic strength saline.

By the way, I entirely agree with the feelings that you posted after this. I think that you were very brave, but absolutely right.

:D:D:D:D

Oh, we just call it normal saline. Thanks for the clarification. I must confess , I don't have any idea what "abnormal" saline might be. Why do we have the need to classify it as "normal"? Any thoughts on this?

Thanks, yes, very brave, but not popular with the big-wigs (people in charge). I decided very early in my career that taking the best care of my patients was my goal. Yes, some things can be "shaken out" in tube testing, but is that best for the patient? NO WAY!!!

There are many, many, many things I don't know about Blood Banking. I will be the first person to admit that. But, what I know , I know. I "stick to my guns", so to speak ,when something comes up I know a bit about. Once again, I'm not totally popular for it!!

OH WELL!!!

Oh, we just call it normal saline. Thanks for the clarification. I must confess , I don't have any idea what "abnormal" saline might be. Why do we have the need to classify it as "normal"? Any thoughts on this?

QUOTE]

I have absolutely no idea why it is called NISS and not NS, but it is referred to as such almost universally throughout the UK.

At one point we were going to call LISS Poor Ionic Strength Solution, but we thought better of it!!!!!!!!!!!

:D:D:D:D