Conflict of interest: Nothing to report.
Cut-off value of red-blood-cell-bound IgG for the diagnosis of Coombs-negative autoimmune hemolytic anemia†
Version of Record online: 11 NOV 2008
Copyright © 2008 Wiley-Liss, Inc.
American Journal of Hematology
Volume 84, Issue 2, pages 98–101, February 2009
How to Cite
Kamesaki, T., Oyamada, T., Omine, M., Ozawa, K. and Kajii, E. (2009), Cut-off value of red-blood-cell-bound IgG for the diagnosis of Coombs-negative autoimmune hemolytic anemia. Am. J. Hematol., 84: 98–101. doi: 10.1002/ajh.21336
- Issue online: 22 JAN 2009
- Version of Record online: 11 NOV 2008
- Accepted manuscript online: 11 NOV 2008 12:00AM EST
- Manuscript Accepted: 7 NOV 2008
- Manuscript Revised: 2 NOV 2008
- Manuscript Received: 7 OCT 2008
- Ministry of Health, Labor and Welfare of Japan
Direct antiglobulin test (DAT)-negative autoimmune hemolytic anemia (Coombs-negative AIHA) is characterized by laboratory evidence of in vivo hemolysis, together with a negative DAT performed by conventional tube technique (CTT) in clinically suspected AIHA patients. The immunoradiometric assay (IRMA) for red-blood-cell-bound immunoglobulin G (RBC-IgG) can be used to diagnose patients in whom CTT does not detect low levels of red cell autoantibodies. We investigated the diagnostic cutoff value of the IRMA for RBC-IgG in Coombs-negative AIHA and calculated its sensitivity and specificity. Of the 140 patients with negative DAT by CTT referred to our laboratory with undiagnosed hemolytic anemia, AIHA was clinically diagnosed in 64 patients (Coombs-negative AIHA). The numbers of Coombs-negative AIHA and non-AIHA patients changed with age and gender. The cutoff values were determined from receiver operating characteristic (ROC) curve according to age and gender. The IRMA for RBC-IgG proved to be sensitive (71.4%) and specific (87.8%) when using these cutoffs. Using these cutoffs for 41 patients with negative DAT referred to our laboratory in 2006, all the pseudonegative cases were treated with steroids before the test. The 31 untreated cases could be grouped using one cutoff value of 78.5 and showed 100% sensitivity and 94% specificity, independent of gender and age. Results indicate that RBC-IgG could become a standard approach for the diagnosis of Coombs-negative AIHA, when measured before treatment. Am. J. Hematol., 2009. © 2008 Wiley-Liss, Inc.