VIDEO: Antibodies of Undetermined Specificity

A recent study has demonstrated that antibodies of undetermined specificity, or AUS, are the most common positive result encountered during gel-based pre-transfusion testing among the general patient population.

In an accompanying editorial in the journal Transfusion, Drs. Christopher Tormey and Jeanne Hendrickson discussed the study.

Here is Dr. Tormey:

“A study in an upcoming issue of Transfusion by Liu & Grossman is the first to quantitatively assess the phenomenon of non-specific results on a large-scale. Surprisingly, non-specific gel reactions (which they have dubbed antibodies of undetermined significance, or AUS) were the single most common positive testing result at their facility. Beyond quantitating the occurrence of AUS, Liu & Grossman also described the natural history of AUS, finding that only a handful of patients with this reaction ultimately develop a specific alloantibody.”

The researchers found that AUS was responsible for 18% of all positive pre-transfusion tests. They also examined data from 45 patients who presented with AUS and had at least one subsequent work-up. AUS was no longer detected in 14 of these patients during follow-up. However, 7 of these individuals subsequently had an identifiable allo-or autoantibody.

Here is Dr. Brenda Grossman, who co-authored the study:

“AUS is a common finding in our pretransfusion testing and even though most represent clinically insignificant antibodies, a fraction may be early developing clinically significant antibodies or clinically significant antibodies to low incident antigens.”

Detection of alloantibodies can be particularly challenging for transfusion laboratories because some alloantibodies rapidly decrease in titer and become undetectable over time. However, these disappearing antibodies can return after transfusion, potentially resulting in hemolysis. Sensitive gel-based or solid-phase screening platforms are available, but often have decreased specificity.

Alternative screening methods may be able to provide similar sensitivity without sacrificing high rates of specificity.

Again, here is Dr. Tormey:

“Platforms such as flow cytometry or single antigen target “one well/one antigen” tests may ultimately offer better and more reliable results. This study is an important reminder that ongoing evaluation of transfusion service policies and laboratory methods remains crucial to ensure patient safety and efficacious testing within the realm of immunohematology.”

We’ll be back on May 30th with another edition of Transfusion News. Thanks for joining us.



1.    Liu C, Grossman BJ: Antibody of undetermined specificity: Frequency, laboratory features, and natural history. Transfusion 2013;53:931-938.

2.   Tormey CA, Hendrickson JE: Antibodies of undetermined significance: Nuisance or near miss? Transfusion 2013;53:926-928.

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