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FIGURE 1: EUROArray procedure


genetic microarray platform which provides fast and easy determination of HLA-DQ2/DQ8, HLA-Cw6, HLA-B27, factor V Leiden and factor II 20210G>A, including fully automated data analysis. In the simple test procedure (figure 1), disease-associated gene sections are amplified from purified genomic patient DNA samples by the polymerase chain reaction (PCR). The fluorescently labelled PCR products are then analysed using slides containing microarray BIOCHIPs (figure 2), which are composed of immobilised complementary probes. Specific binding (hybridisation) of the PCR products to their corresponding microarray spots is detected using a specialised microarray scanner system, and results are evaluated (figure 3) and documented (figure 4) using specially developed software (EUROArrayScan). Certain parameters (currently HLA-B27, factor V Leiden and factor


FIGURE 2: EUROArray slide and enlargement of a BIOCHIP FIGURE 3: Microarray evaluation by EUROArrayScan


II 20210G>A) can be analysed directly from whole blood using the EUROArray Direct procedure (figure 5). The elimination of the DNA isolation step reduces the hands-on time dramatically, and there are no additional costs for DNA isolation kits anymore. In a typical test run with 40 samples, the hands-on time for the whole procedure from blood sample to result is reduced to 1.5 minutes per sample, without compromising the robustness of the test. The sophisticated EUROArray constellations ensure unambiguous identification of the relevant alleles and subtypes. Highly specific primers, ready-to-use PCR components and integrated positive controls all contribute to the reliability of the analysis. Moreover, in contrast to traditionally used cytotoxicity tests, Terasaki methods or FACS analyses that are still applied in some laboratories for HLA-B27 determination, live leukocytes are not required. With microarrays, patient samples can be collected, stored for a time and analysed together as and when convenient.


DETAILED CLINICAL EVALUATION All EUROArrays have been evaluated extensively using


FIGURE 4: Result documentation by EUROArrayScan


precharacterised samples. In a series of studies using a variety of reference methods including DNA sequencing and reference samples from the International Histocompatibility Working Group, each EUROArray demonstrated a 100% concordance with the applicable reference result (table 1). In prevalence studies using panels of randomly selected samples, all


EUROArrays yielded percentages of positivity that were in accordance with known prevalences in the population studied. This amounted to 18% for HLA-Cw6, 9.4% for HLA-B27, 37% for HLA-DQ2/DQ8, 4.2% for factor V Leiden and 1.7% for factor II 20210G>A. Thus, the EUROArray system has demonstrated its ability to


deliver highly reproducible and accurate results in the analysis of genetic determinants.


CONCLUSION FIGURE 5: EUROArray Direct procedure for DNA extraction


The identification of the genetic factors behind diseases such as coeliac disease, psoriasis, ankylosing spondylitis and thrombosis has paved the way for the development of diagnostic microarrays to analyse genetic susceptibility. Specialised microarrays such as the EUROArray provide highly sensitive and specific detection of disease-associated alleles without the need for any previous molecular biology knowledge. As research projects worldwide unravel more of the genome’s secrets, there is enormous potential for further novel diagnostic microarrays. The possibility of preventing and managing disease by means of genetically tailored lifestyle and therapy decisions is a tantalising goal.


REFERENCES References available on request (magazine@informa.com)


030 MEDLAB MAGAZINE ISSUE 1 2012


MAGAZINE


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