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Evaluation and implementation of the gel test for indirect antiglobulin testing in a community hospital laboratory
Insights
The gel test offers a standardized, sensitive, and specific method for antiglobulin testing, proving advantageous for detecting red cell antibodies in transfusion services.
Area of Science:
- Transfusion Medicine
- Immunoserology
- Clinical Laboratory Science
Background:
- The gel test, developed in 1984, aimed to standardize antiglobulin testing.
- It utilizes Sephadex G100 gel to trap red cell-immunoglobulin G (IgG) complexes during centrifugation.
- Detection of agglutination complexes indicates antibody presence, with levels inversely proportional to antibody coating.
Purpose of the Study:
- To evaluate the standardization and simplification of indirect antiglobulin testing using the gel test.
- To assess if the gel test could replace the tube test without compromising quality or increasing costs.
Main Methods:
- A blinded retrospective study using patient sera (n=40) was conducted.
- A nonblinded prospective correlation study (n=121) was also performed.
- The gel test was implemented as the standard method for indirect antiglobulin testing in a community hospital laboratory.
Main Results:
- The gel test detected all 18 known antibodies in positive samples, surpassing the tube method's detection of 16.
- 100% concordance was observed for all negative samples.
- Technologists reported the gel test as easier to read, more reproducible, reliable, and sensitive for weak antibodies.
Conclusions:
- The gel test is a reliable and advantageous method for indirect antiglobulin testing.
- It is appropriate for routine detection and identification of alloantibodies in transfusion service laboratories.
- Implementation led to improved personnel management and successful standardization of testing.
Background:
The gel test, developed by Lapierre in 1984, was designed to standardize antiglobulin testing while improving sensitivity and specificity of the method.
Principle:
Anti-human serum immunoglobulin G (IgG) mixed with Sephadex G100 (gel phase) in a microtube traps red cell-IgG agglutination complexes during migration through the gel in a centrifugation step. Agglutination complexes are visibly detectable at various levels in the microtube as an inverse function of antibody coated on red cells. Unsensitized red cells form a cell pellet at the base of the microtube.
Objective:
To determine if indirect anti-human globulin testing could be standardized and simplified by replacing the tube test with the gel test without compromising quality or increasing costs.
Setting:
A medium-sized community hospital.
Results:
In a blinded retrospective study, we used patient sera (n = 40), which included 10 positive specimens containing 18 known antibodies. Sixteen antibodies were detected and identified with the tube method (1 anti-D and 1 anti-C not detected). By the gel test, 18 antibodies were detected and identified. All negative samples showed 100% concordance. Favorable results were obtained in a nonblinded prospective correlation study (n = 121). Our technologists found the gel test easier to read and more reproducible and reliable than the tube method; they also found increased sensitivity for detecting weakly reacting antibodies. We successfully introduced the gel test into our laboratory as the standard method for indirect antiglobulin testing. Following implementation, improved personnel management was achieved.
Conclusions:
The gel test is a reliable and advantageous method and is appropriate for routine use for detection and identification of alloantibodies in a community hospital transfusion service laboratory.
