Evaluation of the Use of Gel Card System for Assessment of Direct Coombs Test: Weighing the Pros and Cons

Abstract

A positive direct Coombs test (DCT) is the hallmark of diagnosis of immune hemolytic anemias. The reagent used for the test is the Antihuman globulin (AHG), which may be either 'Polyspecific' or 'Monospecific'. The advent of the Gel card systems has made the procedure and interpretation of DCT simpler. Aim of this study is to evaluate three of the various techniques used for the performance and interpretation of DCT. A total of 96 EDTA samples were included in the study. DCT was performed by (i) polyspecific AHG manual tube method (ii) polyspecific AHG Gel card method and (iii) monospecific AHG (Anti IgG and Anti Complement) manual tube method. In our study we considered positivity by monospecific AHG as the standard for diagnosis. Of the total 96 samples evaluated, 44 cases positive by Gel card method, were also positive for either one or both the monospecific AHG reagents. 17 cases positive by Gel card were negative by all manual methods. These false positive cases were attributed to reasons such as increased ESR, macrocytosis and marked leucocytosis. Nine cases were negative by Gel card but were positive with the Monospecific AHG. The sensitivity of DCT done by the Gel card technique was 83.01% and the specificity was 60.46%. Use of Gel card technique to perform and interpret DCT is easier than manual tube methods, but positivity by Gel card needs to be correlated with clinical presentation of the patient and other laboratory findings. Monospecific antisera can be used to confirm cases that are positive by the Gel card systems.

Possible cause of lack of positive samples on homologous blood transfusion

“…Although determination of homologous blood transfusion based on the definition of mixed populations of erythrocytes by flow cytometry, but agglutination methods is commonly used for the identification of RBCs phenotypes. The gel card format of agglutination method that we used for RBCs typing is the easiest, not laborious technique with higher sensitivity than conventional tube technique …”

“…The gel card format of agglutination method that we used for RBCs typing is the easiest, not laborious technique with higher sensitivity than conventional tube technique. [12] The distribution of the samples is given in details in Table 1. In summary, samples from the following sports were analyzed: athletics -209 samples, biathlon -117, cycling -73, cross-country skiing -53, rowing -15, swimming -14, and speed skating -54.…”

The Direct Antiglobulin Test: Indications, Interpretation, and Pitfalls

“…6 Gel and solid phase methods offer several advantages over the tube platform-they are both potentially automat-able and both may be technically less difficult to perform than the tube method. 8 However, they have greater sensitivity than conventional tube testing 6,9 and this increased sensitivity may lead to the detection of clinically insignificant but weakly positive DAT results that sometimes demonstrate negative eluates. 9 CLINICAL APPLICATIONS OF THE DAT There are 3 basic clinical scenarios for which the DAT is used: (1) investigation of suspected alloimmune-mediated hemolytic transfusion reactions, (2) evaluation for HDFN, and (3) investigation of autoimmune-mediated hemolytic anemia.…”

A new reliable test for crossmatching: microplate hydrogel immunoassay technology

“…With these advantages, MGIA‐AHG T is widely used for antibody screening and crossmatching tests. However, with samples involving residual fibrinogen from serum‐based test samples or rarely marked leukocytosis, the sedimentation of RBCs is blocked, which results in false positives (Lee et al ., ; Alwar et al ., ). RBC debris in old specimens tends to float on the surface or in the gel, which also causes false positives (Li & Ma, ).…”