Looking beyond the test

摘要

Autoimmune hemolytic anemia (AIHA) is a rare disease entity with a reported incidence of 0.8/100,000/year.1 It is an immune-mediated process by which antibodies attach to antigens on the red blood cell surface resulting in hemolysis. Causes of AIHA include lymphoproliferative disorders such as chronic lyniphocytic leukemia, medications such as cephalo-sporins, autoimmune diseases such as lupus and viruses such as Epstein-Barr. It has been stated that 50% of cases are idio-pathic.2 The 2 types of AIHA are warm and cold. Warm AIHA is more common, being present in 75% to 90% of cases.3 Warm AIHA is characterized by the presence of IgG antibodies binding to the surface of red blood cells at temperatures of 37°C. The test used to confirm AIHA is the direct antiglobulin test (DAT), which is falsely negative in 5% to 10% of patients.4 This can present a challenge to the physician because waiting for a confirmatory test before initiating treatment may be life threatening to the patient, hi cases such as this, the physician is forced to make a treatment decision based on clinical diagnosis alone, which can be difficult given the rarity of this clinical situation. We present a case of a patient that had suspected ATHA and a,negative DAT to demonstrate how to work through the diagnosis and treatment of ATHA.