A report of a rare case of autoimmune haemolytic anaemia in a patient with Hodgkin's disease in whom routine serology was negative.

Abstract

Autoimmune haemolytic anaemia (AIHA) is an acquired clinical condition which is characterised by the production of auto-antibodies that bind to the surface of circulating erythrocytes, leading to haemolysis and decreased survival of the red blood cells. The estimated yearly incidence of AIHA is 1–3 cases per 100,000 persons in the general population1. The direct antiglobulin test (DAT) is considered to be a cornerstone in establishing the diagnosis of AIHA, since there is uptake of autoantibodies and/or complement components onto the affected red blood cells. In suspected cases of AIHA, a positive DAT is predictive in 83% of patients, but not all cases of AIHA are DAT-positive2. Between 5% to 10% of all cases of AIHA are DAT-negative3. Three causes for this situation have been identified: (i) red blood cell bound IgG molecules, below the threshold of detection of the DAT, (ii) low-affinity IgG autoantibodies that are washed off the red cells during the washing phase for the test, and (iii) red cell bound IgA and rare warm IgM autoantibodies that are not detectable by the routine anti-human globulin reagent3. Given these different possibilities, a negative DAT must be weighed in the light of clinical suspicion. If there is clinical evidence of haemolysis, a thorough investigation with more specialised testing is needed. We report here a case of DAT-negative AIHA in a patient with Hodgkin’s lymphoma which was detected in our hospital blood bank laboratory.