Cross-match test

Carlo Moreschi (1876 - 1921) was the first to describe antibodies circulating in the blood as early as 1908 (Gressner 2013), but it was only in the 1940s that the British pathologist and immunologist Robin Coombs (1921 - 2006) recognised the importance of antibodies (Cruse 2003).

Terasaki and McClelland first succeeded in detecting HLA antibodies in 1964 with the microlymphocyte cytotoxicity test (LCT) developed by them.

In 1983 Garovoy, Rheinschmidt, Bigos et al. presented the flow cytometric method for the determination of HLA antibodies (FCXM) for the first time (Renner 2010).

The cross-match test is the last and decisive immunological test before a (kidney) transplantation. It can detect any preformed antibodies of the recipient against donor HLA antigens (Herold 2020).

Different test procedures exist for the crossmatch test. The two most common procedures are:

• CDC- Crossmatch (Complement-dependent cytotoxicity crossmatch), also called LZT or LCT (lymphocytotoxicity test). This test is the standard procedure in Germany (Kuhlmann 2015 / Schlaf 2013)
• flow cytometric detection (FCXM): The newer FCXM test is independent of the complement binding capacity of the antibodies (Schönemann 2016). It is primarily used as a standard procedure abroad, e.g. in Great Britain (Lindemann 2017).

With regard to the result, the specificity is higher for the CDC, the sensitivity for the FCXM (Wanner 2003).

The cross-match test is always performed before a planned (kidney) transplantation. It is defined as mandatory in the guidelines of the German Medical Association and in the standards of Eurotransplant (since 2010) (Lindemann 2017).

The preformed allo antibodies against HLA antigens of the donor, which can be detected in the cross-match test, can be generated, for example, by:

• blood products
• previous transplants
• Pregnancy (Herold 2020)

In the CDC crossmatch test, the serum of the intended recipient is incubated with T lymphocytes from the donor with the addition of complement (Siegenthaler 2006).

Pathophysiologically, the detection of a positive crossmatch crossmatch test results in acute vascular inflammation, which causes so-called hyperacute rejection (Kasper 2015).

The test takes about 4 hours to perform and thus prolongs the "cold ischemia time" (see kidney transplantation) (Keller 2010).

If the test result is positive, this indicates the presence of preformed donor-specific antibodies in the recipient against HLA class I antigens of the donor (Kasper 2015).

Absolute contraindication: A positive cross match together with A,B,0 incompatibility is the only absolute contraindication for (kidney) transplantation (Kasper 2015).

Acceptable Mismatch- Program: Since a large number of dialysis patients are already highly immunized and have HLA- AK, they would have a much worse chance of being assigned a transplant. Therefore, a so-called AM program (Acceptable Mismatch Program) was developed, for which the probability with which the HLA characteristics of donor and recipient largely match can be calculated with the help of the Mismatch Probatility = MMP (Bundesärztekammer 2013).

Therefore, the following blood group rules apply to highly immunized patients enrolled in the AM- program:

• Donor 0 Recipient 0, A, B, AB
• Donor A Recipient A, AB
• Donor B Recipient B, AB
• Donor AB Recipient AB (Herold 2020)

HLA mismatches: The type of HLA mismatch also plays a role. HLA- DR- mismatches are prognostically unfavorable, followed by HLA- B- mismatches. HLA- A- mismatches, on the other hand, play only a minor role (Geberth 2011).

Panel reactivity determination: To reduce the possibility of a positive cross-match test prior to transplantation, patients on the transplant waiting list are regularly screened for HLA- AK every 3 months by the so-called panel reactivity determination (Herold 2020). The result is reported to Eurotransplant to minimize the possibility of potential organ donations with non-acceptable HLA antigen differences (NAHA) and thus with a positive cross- match test (which would prolong the cold ischemia time) (Süsal 2014).

Immunological conditioning

Another way to improve the chances in the allocation of a transplant is immunological conditioning.

This is possible through different measures. The most common are:

• i. v. administration of high-dose immunoglobulins (IVIgs).
• Combination of low-dose IVIgs plus plasmapheresis

(Keller 2010)

1. Cruse J M et al (2003) Illustrated Dictionary of Immunology. CRC Press 170
2. Geberth S et al (2011) Practice of dialysis according to the guidelines NKF KDOQITM, KDIGO, EDTA, DGfN. Springer Verlag 258 - 259, 267, 271
3. Gresner A M et al (2013) Lexicon of Medical Laboratory Diagnostics. Springer Publishing House 254
4. Herold G et al (2020) Internal medicine. Herold Publisher 647
5. Kasper D L et al (2015) Harrison's Principles of Internal Medicine. Mc Graw Hill Education 1827
6. Kasper D L et al (2015) Harrison's Internal Medicine. Georg Thieme Publisher 2248
7. Keller C K et al (2010) Practice of nephrology. Springer Publishing House 296
8. Kuhlmann U et al (2015) Nephrology: Pathophysiology - Clinic - Kidney replacement procedure. Thieme Publishing House 767, 779
9. Lindemann M et al (2017) The flow cytometric compatibility test - more sensitive diagnostics for the prediction of transplant rejection. Transfusion medicine - immunohaematology - haemotherapy - transplantation immunology - cell therapy (7) 233 - 237
10. Renner F C (2010) Incidence and specificity of HLA-DR antibodies in sera of kidney transplanted patients. Inaugural- Doctoral thesis for the degree of Doctor of Medicine of the Department of Medicine of the Justus-Liebig-University Gießen. VVB Laufersweiler Publishing House 19
11. Schlaf G (2013) The tolerance test for the exclusion of donor-specific anti-HLA antibodies: Essential for organ survival - but as a result manipulable by interfering factors. 21st annual conference, working group kidney transplantation of the DGU; Halle
12. Schönemann (2016) HLA antibodies before and after kidney transplantation: Transplant in safe hands. Trillium Diagnostics 14 (2): 132 - 134
13. Siegenthaler W et al (2006) Clinical pathophysiology. Georg Thieme Publisher 975
14. Süsal C et al (2014) Recommendations of the German Society of Immunogenetics (DGI) for the determination of unacceptable HLA antigen differences (NAHA) in kidney transplant recipients
15. Wanner C et al (2003) Dialysis procedures in clinic and practice: technology and clinic. Georg Thieme publishing house 596