AUTOIMMUNE HEMOLYTIC ANEMIA ASSOCIATED WITH COLD
a. Cold Agglutinin Syndrome. This is the most common type of autoimmune
hemolytic anemia associated with cold antibodies, comprising approximately 16 to 25
percent of immune hemolytic anemia. It can occur as an acute or chronic condition.
The acute cases are often associated with Mvcoplasma pneumonias while, on rare
occasions, they are associated with infectious mononucleosis, the hemolysis in these
cases being transient. Patients with chronic primary cold agglutinin syndrome are often
elderly, and present with chronic hemolytic anemia of mild to moderate intensity with, in
cold weather, Raynaud's phenomenon, and, often, hemoglobinuria.
(1) Special technical considerations. It is preferable, if the blood is collected
from the patient at 37C. To do this properly, blood should be collected in a warmed
syringe or Vacutainer tube and immediately placed in a 37C water bath or thermos
flask. If the samples cannot be collected at 37C, they should be incubated at 37C as
soon as possible to allow autoagglutination to disperse. Fortunately, being a reversible
reaction, the cold autoagglutinin will elute back into the serum from the cells. If gross
autohemolysis has already occurred, fresh samples will have to be collected and the
precautions previously mentioned should be taken. The serum should be separated by
centrifuging the blood at 37C. Ideally, this means working in a 37C warm room or
using a heated, jacketed centrifuge. If these are not available, the tubes should be
centrifuged in buckets containing water at about 40C. The RBCs should be washed in
37C to 40C saline before they are used for grouping or direct antiglobulin tests.
Following washing, it is wise to check that all autoagglutination has been dispersed.
(2) Direct antiglobulin test. Only complement is detected on the RBCs. The
lgM cold autoagglutinin sensitizes the patient's RBC in the peripheral circulation where
the temperature falIs below 32C. The IgM-sensitized cells also become sensitized with
complement (C3 and C4 in particular). On recirculating to 37C, the lgM cold antibody
eluate backs off into the serum leaving the cells sensitized with complement. The C3 is
acted on by C3 inactivator to leave only a fragment of C3 (C3d) on the RBCs, which is
detectable by the anti-C3d in antiglobulin serums; C4d may also be present on the
(3) Eluate from RBCs. If the RBCs have been properly collected and
washed at 37C, no activity will be found in the eluate as only complement is present on
the RBCs in "vivo" at 37C.