Red cell agglutination

It is caused by the surface of the red cells being coated with antibodies.

People may develop cold agglutinins from lymphoproliferative disorders, from infection with Mycoplasma pneumoniae or Epstein–Barr virus, or idiopathically (without any apparent cause).

Red cell agglutination can also occur in paroxysmal nocturnal hemoglobinuria[2]: 13 [3] and warm autoimmune hemolytic anemia.

[3] Red blood cell aggregates are counted as single cells by the automated analyzers used to run complete blood count tests.

[6]: 141, 262  If the causative antibodies are only active at room temperature, the agglutination can be reversed by heating the blood sample to 37 °C (99 °F).