Positive direct antiglobulin test

What it means

A positive result of the direct antiglobulin test (DAT), a method of demonstrating the presence of antibody or complement bound to red blood cell (RBC) membranes by the use of anti-human globulin to form a visible agglutination reaction.

The DAT is a method used to detect immunoglobulin or complement bound in vivo to RBCs, using anti-human reagents. There are 3 different reagents that may be used: monospecific reagents to detect either bound immunoglobulin G (IgG) or bound complement (C3) and polyspecific reagents that can simultaneously detect IgG and/or C3. In screening of RBCs for the presence of bound globulins and/or C3, many laboratories may choose to use the polyspecific reagent initially (ie, as a screen for any bound IgG and/or complement) and, if positive, subsequently use monospecific reagents to specifically distinguish what is bound to the RBC surface.

Rare diseases that can present with this2

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category