The role of conventional tube and column agglutination technique in predicting hemolysis in various clinical conditions

Abstract

Introduction: The correlation of positive result in direct antiglobulin test (DAT) with in vivo hemolysis is important for the patient management. This study compares the correlation of tube-DAT and -DAT by column agglutination technique (CAT) with in vivo hemolysis and reviews the appropriateness of the requests for DAT in patients with various clinical conditions. Patients and Methods: A total of 250 consecutive patients referred for DAT were enrolled for the study. Laboratory indicators of hemolysis were obtained from the computerized hospital data management system. Hemolysis in patients was graded using predetermined criteria. DAT was done using CAT and tube techniques and graded on the agglutination pattern. Results: Among 250 patients studied, 160 patients were from the hemato-oncology unit, and 47 had an autoimmune disease. Laboratory evidence of hemolysis was seen in 170 patients (severe: 45.88% and moderate: 54.12%). Positive DAT by tube technique was seen in only 41 out of 65 patients whose DAT was positive by CAT. Hemolytic anemia was the single largest cause in this group. Positive predictive values (PPVs) of tube and CAT were comparable. On comparing the strength of agglutination with the in vivo-hemolysis, 1+ reaction by CAT had low PPV. Conclusion: The present study shows that mere DAT positivity does not always indicate in vivo hemolysis. Hence, while recommending the routine use of CAT for DAT, we suggest to incorporate the strength of agglutination reaction in laboratory report for the ease of interpretation.

Keywords

• Autoantibody
• column agglutination technique
• direct antiglobulin test
• hemolysis
• tube test