Living the best of both worlds: A personal scientific journey

Opportunity is the essence of a career in science or medicine and this continues to be a major source of satisfaction for the many scientists and health care providers worldwide. Having trained as a PhD scientist, the world of clinical medicine seemed to be a galaxy away. I could not have been more wrong in that assumption. Here, I tell the story of my career trajectory so that those new to the sciences understand the potential and the opportunities afforded by a career in clinical laboratory medicine.

Forensic identification of urine samples: a comparison between nuclear and mitochondrial DNA markers

Urine samples from 20 male volunteers of European Caucasian origin were stored at 4 degrees C over a 4-month period in order to compare the identification potential of nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) markers. The amount of nDNA recovered from urines dramatically declined over time. Consequently, nDNA likelihood ratios (LRs) greater than 1,000 were obtained for 100, 70 and 55% of the urines analysed after 6, 60 and 120 days, respectively. For the mtDNA, HVI and HVII sequences were obtained for all samples tested, whatever the period considered. Nevertheless, the highest mtDNA LR of 435 was relatively low compared to its nDNA equivalent. Indeed, LRs obtained with only three nDNA loci could easily exceed this value and are quite easier to obtain. Overall, the joint use of nDNA and mtDNA markers enabled the 20 urine samples to be identified, even after the 4-month period.

Influence of post-mortem changes on DNA typing (D1S80, TH01, HLA DQA 1, and PM typing system): case studies for personal identification

Between 1996 and 2002, we tested a total of 20 unidentified bodies for DNA typing. We describe here the relationships among detection rates achieved by four DNA typing systems (D1S80 typing, TH01 typing, HLA DQA1 typing, and PM typings), the post-mortem interval, types of specimens (bone, nail, and blood), post-mortem changes, and the site at which the corpse was found (indoors, outdoor, or in the sea). Detection rates for PM typings, HLA DQA1 typing, TH01 typing, and D1S80 typing in all cases were 94.7, 90.0, 73.7, and 50.0%, respectively. The success of the typings was highly influenced by the post-mortem interval. Using blood, almost all DNA types were detected, while the nail showed comparatively higher detection rates than bone. The detection rate decreased in order with indoor, outdoor, sea, and soil as the site at which the corpse was found. It is important to consider the specimen, the site at which the corpse was found, and the post-mortem interval to successfully achieve DNA typing.

Genotyping for DQA1 and PM loci in urine using PCR-based amplification: effects of sample volume, storage temperature, preservatives, and aging on DNA extraction and typing

Urine is often the sample of choice for drug screening in aviation/general forensic toxicology and in workplace drug testing. In some instances, the origin of the submitted samples may be challenged because of the medicolegal and socioeconomic consequences of a positive drug test. Methods for individualization of biological samples have reached a new boundary with the application of the polymerase chain reaction (PCR) in DNA profiling, but a successful characterization of the urine specimens depends on the quantity and quality of DNA present in the samples. Therefore, the present study investigated the influence of storage conditions, sample volume, concentration modes, extraction procedures, and chemical preservations on the quantity of DNA recovered, as well as the success rate of PCR-based genotyping for DQA1 and PM loci in urine. Urine specimens from male and female volunteers were divided and stored at various temperatures for up to 30 days. The results suggested that sample purification by dialfiltration, using 3000-100,000 molecular weight cut-off filters, did not enhance DNA recovery and typing rate as compared with simple centrifugation procedures. Extraction of urinary DNA by the organic method and by the resin method gave comparable typing results. Larger sample volume yielded a higher amount of DNA, but the typing rates were not affected for sample volumes between 1 and 5 ml. The quantifiable amounts of DNA present were found to be greater in female (14-200 ng/ml) than in male (4-60 ng/ml) samples and decreased with the elapsed time under both room temperature (RT) and frozen storage. Typing of the male samples also demonstrated that RT storage samples produced significantly higher success rates than that of frozen samples, while there was only marginal difference in the DNA typing rates among the conditions tested using female samples. Successful assignment of DQA1 + PM genotype was achieved for all samples of fresh urine, independent of gender, starting sample volume, or concentration method. Preservation by 0.25% sodium azide was acceptable for sample storage at 4 degrees C during a period of 30 days. For longer storage duration, freezing at -70 degrees C may be more appropriate. Thus, the applicability of the DQA1 + PM typing was clearly demonstrated for individualization of urine samples.