Diagnostic Molecular Biology
PathWest, QEII Medical Centre, Clinical Biochemistry, Nedlands, Western Australia 6009 Royal Perth Hospital, Biochemistry Department, Perth, WA 6001, Australia. For correspondence: Dr John Beilby e-mail: John.Beilby@health.wa.gov.au
Diagnostic molecular biology is arguably the fastest growing area of laboratory medicine and hasthe potential for a major impact on clinical medicine within the next decade. As this area develops, so will our understanding of how structural variations in DNA and RNA are associated with the development of chronic diseases. New technologies have contributed to the dramatic acceleration in our capacity to investigate the genetic components of disease. Future developments in this area will befuelled by improvements in technology and the availability of large, carefully documented study populations. Many genes responsible for monogenic diseases have been successfully isolated and are used for the clinical diagnosis of disease, identiﬁcation of gene carriers or predictive testing of subjects who may develop certain diseases. Genes that cause complex diseases, such as cardiovasculardisease, asthma and osteoporosis are being studied but it will take time before the use of these genetic risk factors are used in clinical practice due to the complexity of the interactions between genetic and environmental risk factors. Diagnostic molecular biology is widely used in a number of areas including haematology, immunology and microbiology with possibly the least developed area beingclinical biochemistry. Apart from diseases such as cystic ﬁbrosis and genetic haemochromatosis, most genetic diseases tested for in clinical biochemistry laboratories are rare in the general population. However, molecular methods will be increasingly incorporated into all areas of pathology, not to replace current tests but as an aid in evaluating the future risk of disease. In this issue of the ClinicalBiochemist Reviews a series of manuscripts have been selected that highlight a snapshot of the 'state-of-art' of diagnostic molecular biology testing in clinical laboratory medicine.
The opening article by Siah et al. provides a comprehensive review of iron metabolism and pathophysiology of iron overload. The identiﬁcation of the HFE gene by Feder et al. in 1996 was a major step forward inunderstanding iron metabolism and has provided considerable impetus to the study of iron metabolism. Genotyping for the common variants of the HFE gene is the most requested genetic test performed in clinical medicine. Possibly because it was the ﬁrst genetic test to be listed for reimbursement on the Medicare Beneﬁt Schedule for patients with an elevated transferrin saturation or serum ferritin; orfor a patient who has a ﬁrst degree relative with haemochromatosis or a relative with homozygosity for the C282Y genetic mutation, or compound heterozygosity (www. medicareaustralia.gov.au). In 2004/05 there were 39,404 HFE tests claimed through Medicare at a cost of $1,257,832. Pharmacogenomics is the study of the effect of genetic variations on drug response, efﬁcacy, and metabolism. This areahas the potential to be one of the ﬁrst large-scale clinical applications of diagnostic molecular biology. It is certain to have an enormous impact on the practice of clinical medicine by deciding on the most effective choice of drugs and avoiding their potentially dangerous side effects. However, to-date there are very few examples of polymorphisms that have a clinically relevant effect on drugresponse. It is likely that drug response will be complex, inﬂuenced by the environment and multiple genetic factors. In the second article in this issue, Dr Jan van der Weide and Dr John Hinrichs from the Department of Clinical Chemistry, St Jansdal Hospital, Harderwijk, The Netherlands discuss the role of pharmacogenomics on the metabolism of antipsychotic and antidepressant drugs. They note...