The role of genetic diagnosis in clinics--from the choice of ordering until reading the data

Genetic diagnosis is a revolutionary method that makes possible simultaneous viral isolation (detection) and identification. The method is so specific, sensitive, and rapid (non-culture) that leads not only to the diagnosis of viral infection, but also to prediction of the chemotherapy, monitoring during the therapy, and judging the efficacy of the treatment. Moreover, it contributes to understanding the disease pathophysiology. The qualitative results are sufficient for diagnosis, but quantitative analysis is sometimes necessary for the prediction of the efficacy and monitoring during treatment. It occasionally requires the numbers of genomic expression, the number of DNA/RNA copies, and the detection of point mutations for drug resistance. Many emerging and re-emerging infectious diseases, such as AIDS and viral hepatitis, are induced by viral infection via blood. The main causative agents of blood-borne viral infection are hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), human T cell leukemia virus type 1 (HTLV1), cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human parvovirus B19. They play main roles in viral hospital infection. The risk of them being transmitted by transfusion of screened blood is very low, but it is always possible that infection may occur in a window period even after extensive blood screening tests. Therefore, to shorten a window period, genetic examinations will be accepted for screening tests in the near future. Prioritization of genetic examinations is needed to select the adequate method and sampling. After examinations, false positive and false negative results have to be extensively read out whether due to contamination or inhibition by agent such as heparin and hemoglobin. The causative virus should be decided by carefully eliminating passenger viruses or latent viruses. Because genetic examinations are so useful but occasionally yield false positive and negative results, genetic diagnosis should be judged totally by combination with other examinations, clinical signs, and clinical symptoms.