Antibody Panel

How to solve a basic antibody panel:
Panels are like a logic puzzle. They may seem overwhelming at first glance but they’re actually simple once you understand them.

The goal of the panel is to figure out an unknown antibody. The overall concept is a patient’s serum is tested against a series of reagent cells with different antigen combinations. After you have gotten your results for how the patient’s serum tested with each reagent cell line you can begin to eliminate antigens. Ideally, you would test the patient’s serum against all antigens individually but this would be time consuming and resource heavy, so the panel was created.

The first step is to look at all the patient reactions that are negative, meaning there was no agglutination between the patient serum and the reagent cell line. You then cross out the ‘plus signs (+)’ on that reagent cell line. Since there was no reaction with the patient serum you can cross it out but not rule it out quite yet.

To rule out an antigen it must be homozygous positive. For example, if a patient tested negative for a cell line that was heterozygous for Duffy, (Fya+, Fyb+), you can’t rule out either due to the heterozygosity. What does that mean? Heterozygous means you have two different alleles on each gene from mom and dad. Homozygous means you have the same allele on each gene from mom and dad. Ok, so why can’t heterozygous lines be ruled out? They can’t be ruled out because there is less of the antigen present on that reagent cell line which could cause a weaker reaction. Generally you want to rule out antigens that have homozygous reagent cell lines, however, there are a few exceptions.

C, E, and K can all be ruled out with a heterozygous reagent cell line.

The next step is to look at the reagent cell lines that tested positive for agglutination and look for a pattern with the remaining antigens.

Phases:
When running an antibody panel using tubes, there will be an immediate spin (IS) phase, 37C phase, and AHG phase (can also be called IAT phase). Since antibodies react differently depending on the conditions different results can be seen in different phases. Results from these phases can provide clues to a potential type of antibody. For example, if a reagent cell line in a panel has no reaction at IS but has a reaction at 37C and AHG, this guides you toward a warm IgG antibody. If there is a reaction only in the AHG phase, this points you toward an IgG antibody.

A few other logical tips:

1. When the patient result shows agglutination with a reagent cell line but the antigen has a zero, this doesn’t rule out the antigen. The antigen actually had no chance to bind with the antibody because it’s not on the reagent cell line.

2. To rule an antigen in or out you want to have at least three cell lines that are the same as your call. This helps to eliminate potential error that could’ve occurred in a single tube.

3. Check the autocontrol. If the autocontrol is positive, the results of the rest of the panel are in question.