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I just answered this question. My Score PASS

You bring up some interesting points and I agree with your position. Certainly "the literature" regarding the clinical importance of titration results is confusing. Most of the original work was done on anti-D, using an unorthodox test protocol (I believe the titrant was a high concentration of BSA), but there did seem to be some correlation between titration strength and clinical impact. Workers attempted to shoe-horn other specificities into the same program, with mixed success. Now, today, as you point out, the gel test is becoming a routine way to measure antibody strength. I don't think anyone honestly knows what the titration end-points mean, since the modern results are difficult to interpret/compare to the older literature. Time will tell. I think people have been caught in a little trap with regard to the controls needed for titrations. It is very unusual to have two sequential samples in a clinical assay, even rarer that one of said samples has been stored (frozen). Consider a simple CBC.....many patients with extended hospital stays have multiple tests performed. Their last samples are not run in parallel with the current sample, yet the results are considered valid because the instrument's controls performed as expected - this is the equivalent of using material with a known potency as a control for patient sample testing. The art is in selecting your control.

I just answered this question. My Score PASS

I just answered this question. My Score PASS

"Tube testing is notoriously variable, while gel testing is believed to reduce some of those nuances. " Yes, but it is also - according to years of CAP survey results - routinely 1-2 endpoints higher on every titration run. So, make sure you are telling your physicians that your facility is doing titers with gel and that the actionable titers for their patients might be at higher endpoints than those historically with tube testing. "It does need to be reliable/robust and give the same end point each time, even with the acknowledged variations in serological tests (reagents, test cells, techs, etc.)" I wonder if the inspector would have been OK with procedures with this kind of control if it was used when there was no retained sample (no control avail) and not used when the new specimen was run in parallel with it's retained pair (internal control avail)?? I guess we will have to see, because that is what we are going to try doing.

Did "they" expand on what they think of as "a decent reaction"? This sounds very subjective to me.

Actually, I was talking to an Ortho tech the other day in regards to another issue, and asked them about their QC for gel panels. They said they test each antigen on each cell to make sure that they get a decent reaction (pos or neg depending). Did not ask what they used for QC anti-sera though. sCOTT

Here's my 2-cents, 2-pennies, or 2-any other small denomination coins: First, I am NOT a regulatory expert, but I am familiar with assay development and validation. All assays should be controlled in some fashion, to give the practitioners some confidence that the results are valid AND that batch-to-batch variation is limited. In a titration, especially a serological titration, this is a little more difficult than having one or two pass/fail samples that are typically included in many laboratory tests. If a control is needed for a titration, it doesn't need to be the same specificity as the test antibody (as Malcolm highlights). Ideally, yes, but not necessarily. It does need to be reliable/robust and give the same end point each time, even with the acknowledged variations in serological tests (reagents, test cells, techs, etc.). Tube testing is notoriously variable, while gel testing is believed to reduce some of those nuances. As Malcolm suggests, it might be necessary to have a control for an IgM titration (ABO) and/or a different one for an IgG titration. At the very least, the end-points may be different. An IgM control might be as simple your routine anti-A reagent; a simple IgG control might be an IAT-reactive anti-D or other specificity. A clever option might be a control that contains both - an IgM component and an IgG component. If a test system is adequately controlled each time (and passes), in my opinion, there is no reason to routinely perform parallel testing of successive patient samples. Retention samples might be useful for investigatory reasons if/when a patient's antibody titration changes radically from one sample to the next, or if there's some other medical indication. I getting a sense of deja vu, I think I've written this before.

We do perform in parallel if we have a previous specimen from the same pregnancy.

Way back in 2003, the AABB published "Guidelines for Implementing an Electronic Crossmatch". In the section REQUIREMENTS on page 4 "Additional criteria suggested, but not universally accepted, include: ... The antibody screen should include a three- or four-cell sample." No further explanation was given but presumably it was for the reasons stated above that you are likely to have more cells with a homozygous antigen expression in a 3-cell panel than you are in a 2-cell panel. Most manufacturers of 3-cell panels make sure to include cells that are homozygous for Duffy and Kidd to avoid missing those. So long story short....that's why we use a 3-cell panel as part of our due-diligence of providing blood by computer assisted crossmatch.