European Journal of Cardiovascular Medicine

Compatibility or pre-transfusion testing involves the cross matching of donor blood with patient blood (of appropriate ABO and Rh type) for the patient who requires  blood transfusion. The donor blood selected is considered compatible if there is no observable reaction in the compatibility tests between the blood of donor and blood of patient.⁽¹⁾ Since the discovery of the ABO system and red cell agglutination by Landsteiner in 1900 and development of the antiglobulin test by Coombs et al. in 1945, the immune hematologists are trying to establish and improve various serological investigations in human blood.⁽²⁾ Spin tube method has been the conventional method for compatibility testing and cross matching in transfusion medicine. ⁽³⁾ Lapierre introduced gel tests through sephadex gel contained within a micro tube using the principle of controlled centrifugation of red cells. The gel technique is useful for ABO and Rh typing, cross matching, Direct and Indirect Antiglobulin Tests (DAT and IAT) and identification of alloantibody. ^(4-5)

Routinely, the tube method is used for cross matching of blood, which involves washing steps and takes 60 minutes. In gel card technique washing steps are not required and the time taken is only 30 minutes ⁽⁶⁾. The gel test is a reliable and advantageous technique and is appropriate for identification of all-antibodies in routine use for detection and identification of blood bank service.⁽⁷⁾

Nowadays, the gel card technique is used as a replacement to conventional tube technique on an automation platform and considered a better method than CTT. CTT is still considered as a gold standard technique in pretransfusion testing despite various disadvantages and having subjective variations among laboratory personnel at times.

The present study is done to evaluate the efficacy of Metrix Micro typing gel method over the conventional tube method in our department.

Aim and Objective - To evaluate the efficacy of  Micro typing gel method over the conventional tube method for compatibility testing.

This is a cross sectional study in which 700 samples were included which were referred to the blood center of the tertiary care center for compatibility testing.

Material and reagents used are: blood sample, test tubes, slides, table top  and gel card centrifuge, incubator, ABO-Rh reagent, Coombs sera, “LISS/ Coombs” and normal saline.  

The blood samples of donor and recipients and blood bags supposed to be transfused are tested for blood groups by antisera A, B and RhD. After blood group confirmation, compatibility testing was done by following techniques:

1. Saline Tube Method: This method is used for performing Major and minor cross match. Firstly, 5% red cell suspension was prepared. Then serum and 5% red cell suspension were mixed in the labeled tubes in the ratio of 2:1 and incubated at 37°C for 30-60 minutes. The tubes were centrifuged at 1000 RPM for 1 minute and observed for agglutination. The cells were washed 3-4 times to remove any unbound antibody. After adding AHG, the tubes were centrifuged again and observed for agglutination. Check cells were added to all negative tubes for confirmation of results.

2. Gel card technique for AHG crossmatch - The microtubules of the Gel-Card LISS / Coombs containing poly specific AHG, are used for cross matching. 50μl of 0.8 % donor’s red cells suspension was added to the microtube of the gel card, followed by 25μl of the patient’s serum. The gel card was incubated at 37⁰ C for 15 minutes then centrifuged in card centrifuge for 10 minutes at 880 rpm and result is observed as agglutination reaction for which grading is done as follows-

No agglutination: - compatible

Agglutination: - incompatible Grading of positive result

Grade 4:-Indicated by a solid band of red cells on the top of gel.

Grade 3:- Indicated by red cells agglutinates in the upper half of gel.

Grade 2:- Indicated by red cells agglutinates dispersed throughout the column.

Grade 1:- Indicated by red cells agglutinate mainly in the lower half of the column.

            All samples were cross matched by both methods i.e. by conventional spin tube method with AHG and without AHG and by Gel card system (“LISS/Coombs micro typing system containing specific antihuman globulin with Anti IgG, C3d activity). Major crossmatch was performed for each patient. In which patient serum or plasma and donor red cells suspension are combined, then centrifuged, and observed for agglutination

In our study, 700 blood samples were cross-matched using Spin saline tube method with and without AHG and Matrix Gel Card method. Various observations of the study are explained in tables below.

Table 1 shows, out of 700 cases, majority cases were female (64%) and 36% were male. Male to female ratio was 0.56:1.

Table 2 shows, out of 700 cases , most of cases (38%) belong to age group of 21 to 40 years followed by 1 to 10 years (25%) , more than 40 years(19%), 11 to 20 years (11%) and up to one year(7%) respectively.

Table 3 shows that Out of 700 cases, the majority of patients (38%) were transfused for having severe anemia, 28 % cases for anemia with ANC, 22 % cases for sickle cell disease, 6% for thalassemia and surgical indication.

The purpose of the study was to evaluate the gel approach and the traditional tube technique for blood cross matching. 700 patients’ samples were tested in conventional tube technique as well as by the gel technique.

In our study, 692 samples showed compatibility in CTT without AHG and were considered as true negative. Out of 08 samples which were incompatible, 04 samples were found to be compatible and 04 samples were incompatible, when subjected to CTT with AHG. Hence these 4 samples appear to be false positives. In the gel card method out of 700 samples, 696 showed crossmatch compatibility (true negative) and 04 samples showed crossmatch Incompatible(true positive), showing comparable results with conventional tube technique. Our findings are in agreement with other studies kaur R et al⁽⁸⁾ (2003) , Jai prakash et al⁽⁹⁾ 2006, Novaretti MCZ et al⁽¹⁰⁾  (1994) Gond SK et al⁽¹⁴⁾, 2016, Singh DN et al⁽¹⁵⁾  2017 , Dhariwal SK et al⁽¹⁶⁾ 2017 , Gulati P et al⁽¹⁷⁾ 2020 , Singh R et al⁽¹⁸⁾ 2020 , Rajnitha V et al⁽¹⁹⁾ 2022 , Swarup D et al⁽²⁰⁾ 2008        

The sensitivity and specificity of the gel card method with respect to the tube method in our study was 100 % and 100 % respectively. which is similar to the study of  Reena Sharma et al⁽¹²⁾, 2020 and Swarup D et al⁽²⁰⁾, 2008

Our study showed sensitivity and specificity of conventional tube technique with AHG and  conventional tube technique without AHG method is100% and  99.4% respectively, which is similar to study conducted in South Carolina by John et al⁽¹³⁾ (1999) which showed sensitivity of gel card 95% and saline tube 99.1% respectively.

In our study the average time taken for the compatibility test for gel card and convention tube technique was 30 min and 64 min respectively which is comparable with the study of Swarup D et al⁽²⁰⁾, 2008 in which average time required for a single compatibility test by Gel card method was approx 15-20 minutes while that for conventional spin tube method was approx 90 minutes including use of AHG (IAT).

In the study  Reeta Taksali et al⁽²⁾ (2016) total number of male subjects was 46% and female subjects were 54%. Male to female ratio was 0.85:1. In our study 64% subjects were female  and 36% subjects were male with male to female ratio of 0.56:1.

The basic principle of the gel test is that instead of a test tube, the serum and cell reaction takes place in a micro tube. Six of such micro tubes are embedded in a plastic card to allow ease of handling, testing, reading and disposal. Gel card method is more sensitive and specific and better than conventional tube methods in terms of perseverance of result for 3-4 days, easy and quicker to perform, Person to person variation in results is absent and a less time consuming procedure, no cell washing is required and ideal for automation. Since gel has already been coated with AHG, there is no separate step of adding Antiglobulin reagents.The only disadvantage of the gel card method  is that gel cards are costly and need special enhancing mediums and instruments for this procedure. So, it is concluded that for routine compatibility testing in blood centers of all hospitals, gel card method is recommended.

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