A colleague comments that according to Table 1.8-1 in the AABB Technical Manual (p. 667, 14th edition), there are ten designations of hemagglutination reactions.

Some of the technologists with whom she works feel that the 2+, 3+ and 4+ reactions should be further subdivided to indicate when a reaction is strong (S), or weak (W). She wonders if other laboratories use 'S' and 'W' notations to subdivide the strength of the antigen-antibody reactions that are between 2+ and 4+? She also wonders if such subdivisions would have serological/clinical implication?

The following input was received in response to the above question:

1. A transfusion medicine physician in Los Angeles acknowledges that he is NOT aware of any publications that demonstrate a clinical significance between a 2+ and a 2+(s) reaction, a 3+ and a 3+(s) reaction, etc, in predicting how a patient's antibody might behave clinically. On the other hand, he believes that minor differences in reactivity might be useful for monitoring a single patient's progress over time to see if an antibody is getting weaker or stronger

2. W. John Judd, FIBMS, MIBiol, Professor of Immunohematology at the University of Michigan Medical Center reports that there are 17 such reaction strength designations in his book! Three of the reaction strength designations deal with two cell populations and three with degrees of hemolysis. Professor Judd comments that the grade assignments to tube reactions, especially the intermediate ones, are highly subjective and vary enormously among technologists. Also, in his experience no two different technologists read the same reaction consistently. Consequently, in his opinion the fine grading of reactions is not helpful in following a patient's progress. For the highly experienced practitioner it is, however, helpful to some degree to use the intermediate grades in antibody identification; one can sometimes pick out a particular specificity or dosing antibody this way. He adds that his book includes a proficiency test on the subject of reaction grading. He concludes by acknowledging that his routine lab technologists do not use intermediate grades; only their reference technologists do. He suspects that reference laboratories most likely use intermediate grades for reporting reactions. Finally, John adds that in case any one is interested in his book, it is sold out. However, a new edition will be out in a year or two.

3. An experienced immunohematologist in Los Angeles reports that his research laboratory has always used "in between grades" (e.g., 1/2+, 1+, 1 1/2+, 2+, 2 1/2+, 3+, 3 1/2+, 4+). This obviously, as with all agglutination results, does not have relevance to clinical significance but he has found it useful over the years in interpreting serological patterns from a general impression point of view and comparative results. Having said that, he does not feel strongly about it; it is just what he personally has done for the last 45 years!

4. A very experienced immunohematologist in the Pennsylvania-New Jersey region reports that the National Reference Laboratory for Blood Group Serology uses the grading scheme of 4+, 3+s, 3+, 2+s, 2+, 1+s, 1+, +m, mf, 0, H. In her experience some labs focus on reactions that are usually positive, such as Immunohematology Reference Labs (IRLs) and others that focus on mostly negatives (such as hospital transfusion services). She thinks that subtle clues to antibody identity are valuable in some settings (the reference labs) and confusing in others. She adds that she has no data to suggest clinical relevance of these subtle differences, but she finds them useful in comparisons of reactivities on a panel. She concludes saying that there are numerous IRLs that use either s or w. Some score reactions on a scale of 1-10 or 1-12 thus making it even more varieties of reactions.

ADDENDA Oct. 4, 2006

5. A very experienced immunohematologist who specializes in R&D for a global in vitro diagnostics company specializing in the area of pre-transfusion diagnostics reports that before automation, he probably would have agreed with subdividing the scoring scheme more than 1+ to 4+, because to do so was useful in panel resolutions, etc. As an aside, his company's manufacturing department actually uses an 18-point hemagglutination tube test scale to distinguish subtle differences in reaction strengths. The enlarged scale is needed to pinpoint subtle performance differences in reagent formulations. He believes the majority of technical staff tend to shake tubes a little gentler when close to the end of a titration endpoint or when very weak reactions are encountered. Blinding samples tends to reduce but not totally eliminate this bias. Negative controls are not always included in testing. He has observed that technologists stop shaking positive reactions when the agglutinates come completely off the bottom of the tube, not when negative pellets are completely resuspended. In contrast, he has not observed noticeable differences in microplate hemagglutination results on automated platforms, possibly because the assay is more reproducible due to narrower tolerances for sample/reagent addition, incubation temperature/time, centrifuge, shake of all wells performed the same, gelatin coated microplate wells to remove problems associated with static electricity/plastic interactions, etc). However, when grading the reactions of the automated testing, they use the following reaction scores (negative and 1+ to 4+).

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