Report into a discordant result at D16S539 between SGM Plus® and PowerPlex® ESI 16 kits in a criminal case sample and implications for the UK National DNA Database upgrade.

Upon re-testing of a DNA extract as part of a defence examination, a discordant result was observed at D16S539. Further STR testing and DNA sequencing of the sample identified the cause as a primer binding site mutation which was shown to be a previously unreported SNP. The testing results obtained in this case are considered in light of the current ongoing Multiplex Upgrade Project in the UK and the likely increase in discordant results that may be observed once different next generation kits are introduced.

A common epigenetic clock from childhood to old age.

Forensic age estimation is a DNA intelligence tool that forms an important part of Forensic DNA Phenotyping. Criminal cases with no suspects or with unsuccessful matches in searches on DNA databases; human identification analyses in mass disasters; anthropological studies or legal disputes; all benefit from age estimation to gain investigative leads. Several age prediction models have been developed to date based on DNA methylation. Although different DNA methylation technologies as well as diverse statistical methods have been proposed, most of them are based on blood samples and mainly restricted to adult age ranges. In the current study, we present an extended age prediction model based on 895 evenly distributed Spanish DNA blood samples from 2 to 104 years old. DNA methylation levels were detected using Agena Bioscience EpiTYPER® technology for a total of seven CpG sites located at seven genomic regions: ELOVL2, ASPA, PDE4C, FHL2, CCDC102B, MIR29B2CHG and chr16:85395429 (GRCh38). The accuracy of the age prediction system was tested by comparing three statistical methods: quantile regression (QR), quantile regression neural network (QRNN) and quantile regression support vector machine (QRSVM). The most accurate predictions were obtained when using QRNN or QRSVM (mean absolute prediction error, MAE of ± 3.36 and ± 3.41, respectively). Validation of the models with an independent Spanish testing set (N = 152) provided similar accuracies for both methods (MAE: ± 3.32 and ± 3.45, respectively). The main advantage of using quantile regression statistical tools lies in obtaining age-dependent prediction intervals, fitting the error to the estimated age. An additional analysis of dimensionality reduction shows a direct correlation of increased error and a reduction of correct classifications as the training sample size is reduced. Results indicated that a minimum sample size of six samples per year-of-age covered by the training set is recommended to efficiently capture the most inter-individual variability..

Characterization of the public transit air microbiome and resistome reveals geographical specificity.

BACKGROUND: The public transit is a built environment with high occupant density across the globe, and identifying factors shaping public transit air microbiomes will help design strategies to minimize the transmission of pathogens. However, the majority of microbiome works dedicated to the public transit air are limited to amplicon sequencing, and our knowledge regarding the functional potentials and the repertoire of resistance genes (i.e. resistome) is limited. Furthermore, current air microbiome investigations on public transit systems are focused on single cities, and a multi-city assessment of the public transit air microbiome will allow a greater understanding of whether and how broad environmental, building, and anthropogenic factors shape the public transit air microbiome in an international scale. Therefore, in this study, the public transit air microbiomes and resistomes of six cities across three continents (Denver, Hong Kong, London, New York City, Oslo, Stockholm) were characterized. RESULTS: City was the sole factor associated with public transit air microbiome differences, with diverse taxa identified as drivers for geography-associated functional potentials, concomitant with geographical differences in species- and strain-level inferred growth profiles. Related bacterial strains differed among cities in genes encoding resistance, transposase, and other functions. Sourcetracking estimated that human skin, soil, and wastewater were major presumptive resistome sources of public transit air, and adjacent public transit surfaces may also be considered presumptive sources. Large proportions of detected resistance genes were co-located with mobile genetic elements including plasmids. Biosynthetic gene clusters and city-unique coding sequences were found in the metagenome-assembled genomes. CONCLUSIONS: Overall, geographical specificity transcends multiple aspects of the public transit air microbiome, and future efforts on a global scale are warranted to increase our understanding of factors shaping the microbiome of this unique built environment.

Body fluid identification using a targeted mRNA massively parallel sequencing approach - results of a EUROFORGEN/EDNAP collaborative exercise.

In a previous study we presented an assay for targeted mRNA sequencing for the identification of human body fluids, optimised for the Illumina MiSeq/FGx MPS platform. This assay, together with an additional in-house designed assay for the Ion Torrent PGM/S5 platform, was the basis for a collaborative exercise within 17 EUROFORGEN and EDNAP laboratories, in order to test the efficacy of targeted mRNA sequencing to identify body fluids. The task was to analyse the supplied dried body fluid stains and, optionally, participants' own bona fide or mock casework samples of human origin, according to specified protocols. The provided primer pools for the Illumina MiSeq/FGx and the Ion Torrent PGM/S5 platforms included 33 and 29 body fluid specific targets, respectively, to identify blood, saliva, semen, vaginal secretion, menstrual blood and skin. The results demonstrated moderate to high count values in the body fluid or tissue of interest with little to no counts in non-target body fluids. There was some inter-laboratory variability in read counts, but overall the results of the laboratories were comparable in that highly expressed markers showed high read counts and less expressed markers showed lower counts. We performed a partial least squares (PLS) analysis on the data, where blood, menstrual blood, saliva and semen markers and samples clustered well. The results of this collaborative mRNA massively parallel sequencing (MPS) exercise support targeted mRNA sequencing as a reliable body fluid identification method that could be added to the repertoire of forensic MPS panels.

A collaborative EDNAP exercise on SNaPshot™-based mtDNA control region typing.

A collaborative European DNA Profiling (EDNAP) Group exercise was undertaken to assess the performance of an earlier described SNaPshot™-based screening assay (denoted mini-mtSNaPshot) (Weiler et al., 2016) [1] that targets 18 single nucleotide polymorphism (SNP) positions in the mitochondrial (mt) DNA control region and allows for discrimination of major European mtDNA haplogroups. Besides the organising laboratory, 14 forensic genetics laboratories were involved in the analysis of 13 samples, which were centrally prepared and thoroughly tested prior to shipment. The samples had a variable complexity and comprised straightforward single-source samples, samples with dropout or altered peak sizing, a point heteroplasmy and two-component mixtures resulting in one to five bi-allelic calls. The overall success rate in obtaining useful results was high (97.6%) given that some of the participating laboratories had no previous experience with the typing technology and/or mtDNA analysis. The majority of the participants proceeded to haplotype inference to assess the feasibility of assigning a haplogroup and checking phylogenetic consistency when only 18 SNPs are typed. To mimic casework procedures, the participants compared the SNP typing data of all 13 samples to a set of eight mtDNA reference profiles that were described according to standard nomenclature (Parson et al., 2014) [2], and indicated whether these references matched each sample or not. Incorrect scorings were obtained for 2% of the comparisons and derived from a subset of the participants, indicating a need for training and guidelines regarding mini-mtSNaPshot data interpretation.

Reactivation of 2 genetically distinct varicella-zoster viruses in the same individual.

Varicella-zoster viruses recovered from 2 episodes of herpes zoster in an immunocompetent man were found to be different genotypes. The fact that the 2 isolates came from the same individual was confirmed by DNA fingerprinting. Immunity following chickenpox may not always protect against systemic reinfection. This finding raises questions about varicella-zoster virus pathogenesis and may have an impact on public health policy.

Analysis of artificially degraded DNA using STRs and SNPs--results of a collaborative European (EDNAP) exercise.

Recently, there has been much debate about what kinds of genetic markers should be implemented as new core loci that constitute national DNA databases. The choices lie between conventional STRs, ranging in size from 100 to 450 bp; mini-STRs, with amplicon sizes less than 200 bp; and single nucleotide polymorphisms (SNPs). There is general agreement by the European DNA Profiling Group (EDNAP) and the European Network of Forensic Science Institutes (ENFSI) that the reason to implement new markers is to increase the chance of amplifying highly degraded DNA rather than to increase the discriminating power of the current techniques. A collaborative study between nine European and US laboratories was organised under the auspices of EDNAP. Each laboratory was supplied with a SNP multiplex kit (Foren-SNPs) provided by the Forensic Science Service, two mini-STR kits provided by the National Institute of Standards and Technology (NIST) and a set of degraded DNA stains (blood and saliva). Laboratories tested all three multiplex kits, along with their own existing DNA profiling technique, on the same sets of degraded samples. Results were collated and analysed and, in general, mini-STR systems were shown to be the most effective. Accordingly, the EDNAP and ENFSI working groups have recommended that existing STR loci are reengineered to provide smaller amplicons, and the adoption of three new European core loci has been agreed.

Inter-laboratory evaluation of the EUROFORGEN Global ancestry-informative SNP panel by massively parallel sequencing using the Ion PGM™.

The EUROFORGEN Global ancestry-informative SNP (AIM-SNPs) panel is a forensic multiplex of 128 markers designed to differentiate an individual's ancestry from amongst the five continental population groups of Africa, Europe, East Asia, Native America, and Oceania. A custom multiplex of AmpliSeq™ PCR primers was designed for the Global AIM-SNPs to perform massively parallel sequencing using the Ion PGM™ system. This study assessed individual SNP genotyping precision using the Ion PGM™, the forensic sensitivity of the multiplex using dilution series, degraded DNA plus simple mixtures, and the ancestry differentiation power of the final panel design, which required substitution of three original ancestry-informative SNPs with alternatives. Fourteen populations that had not been previously analyzed were genotyped using the custom multiplex and these studies allowed assessment of genotyping performance by comparison of data across five laboratories. Results indicate a low level of genotyping error can still occur from sequence misalignment caused by homopolymeric tracts close to the target SNP, despite careful scrutiny of candidate SNPs at the design stage. Such sequence misalignment required the exclusion of component SNP rs2080161 from the Global AIM-SNPs panel. However, the overall genotyping precision and sensitivity of this custom multiplex indicates the Ion PGM™ assay for the Global AIM-SNPs is highly suitable for forensic ancestry analysis with massively parallel sequencing.

Durable remissions of myelodysplastic syndrome and acute myeloid leukemia after reduced-intensity allografting.

PURPOSE: To evaluate the use of reduced-intensity (RI) conditioning with allogeneic hematopoietic stem cell transplantation (HSCT) from HLA-identical family donors in patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). PATIENTS AND METHODS: Sixteen patients (median age, 54 years; range, 37 to 66 years) underwent RI-HSCT using a conditioning regimen of fludarabine 25 mg/m2 daily for 5 days and either cyclophosphamide 1 g/m2 daily for 2 days (14 patients) or melphalan 140 mg/m2 for 1 day (two patients). The median number of CD34+ cells and CD3+ cells infused per kilogram of recipient weight was 4.5 x 106 (range, 1.8 to 7.3 x 106 cells) and 2.9 x 108 (range, 0.1 to 9.6 x 108 cells), respectively. RESULTS: There was no transplant-related mortality (TRM) within 100 days of HSCT. Grade 1 to 2 acute graft-versus-host disease (GVHD) occurred in three patients, but neither grade 3 nor grade 4 disease was observed. Chronic GVHD occurred in 10 patients. One patient had cytomegalovirus (CMV) reactivation but did not develop CMV disease. With a median follow-up of 26 months (range, 15 to 45 months), 11 patients are alive (nine in continuous complete remission and one in complete remission after a second transplantation), and five have died (four from disease progression and one from bone-marrow aplasia induced by cyclosporine withdrawal). The 2-year actuarial overall and event-free survival rates were 69% (95% confidence interval [CI], 40% to 86%) and 56% (95% CI, 30% to 68%), respectively. CONCLUSION: This strategy of RI-HSCT resulted in reliable engraftment with low incidence of acute GVHD and TRM. Durable remissions were observed in patients with MDS and AML consistent with a graft-versus-leukemia effect.

Circadian activity of the endogenous fibrinolytic system in stable coronary artery disease: effects of beta-adrenoreceptor blockers and angiotensin-converting enzyme inhibitors.

OBJECTIVES: To examine circadian changes in the sympathovagal balance, the activity of the renin-angiotensin system and hemostatic variables in patients with stable coronary artery disease, and the effects of beta-adrenoceptor blockade and angiotensin-converting enzyme inhibition. BACKGROUND: Sympathovagal balance and key components of the fibrinolytic system show circadian variability. The effects of beta-adrenergic blocking agents and angiotensin-converting enzyme inhibitors on these autonomic and hemostatic rhythms are not well defined. METHODS: Twenty patients with coronary artery disease underwent 24-h Holter monitoring for heart rate variability and blood sampling (6 hourly for 24 hours) after three consecutive treatment phases, (firstly with placebo, then bisoprolol, and finally quinapril). The effects on sympathovagal balance, hemostatic variables and the renin-angiotensin system activity were measured. RESULTS: The fibrinolytic capacity showed marked circadian variation at the end of the placebo phase (p = 0.002), plasminogen activator inhibitor-1 (PAI-1) activity peaking at 06.00 AM when tissue plasminogen activator (tPA) activity was at its nadir. Sympathovagal balance showed a sharp increase at approximately the same time but plasma renin activity did not rise until later in the day. Inspection of the 24-h profiles suggested that bisoprolol reduced sympathovagal balance and the morning peak of PAI-1 activity and antigen, with a small increase in tPA activity, although these changes were not significant. Quinapril produced a substantial rise in renin (p = 0.01) but did not significantly affect either PAI-1 or tPA. Sympathovagal balance was unaffected by quinapril. CONCLUSIONS: In patients with stable coronary artery disease, angiotensin-converting enzyme inhibition with quinapril does not affect either sympathovagal balance or the endogenous fibrinolytic system. Our data suggest that the sympathoadrenal system may modify fibrinolytic activity, judged by the response to beta-adrenoreceptor blockade with bisoprolol.

Y chromosome STR haplotypes in three UK populations.

Eleven Y chromosome short tandem repeat markers: DYS19, DYS385, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438 and DYS439, have been typed in the three main UK population groups: Caucasians, Afro-Caribbeans and South Asians. Existing PCR reactions were adapted to incorporate DYS437, DYS438 and DYS439. The observed 11 loci haplotypes and the individual allele frequencies for each locus are presented. Distinct differences for most markers were observed between the population groups studied.

RNA/DNA co-analysis from human skin and contact traces--results of a sixth collaborative EDNAP exercise.

The European DNA profiling group (EDNAP) organized a sixth collaborative exercise on RNA/DNA co-analysis for body fluid/tissue identification and STR profiling. The task was to identify skin samples/contact traces using specific RNA biomarkers and test three housekeeping genes for their suitability as reference genes. Eight stains, a skin RNA dilution series and, optionally, bona fide or mock casework samples of human or non-human origin were analyzed by 22 participating laboratories using RNA extraction or RNA/DNA co-extraction methods. Two sets of previously described skin-specific markers were used: skin1 pentaplex (LCE1C, LCE1D, LCE2D, IL1F7 and CCL27) and skin2 triplex (LOR, KRT9 and CDSN) in conjunction with a housekeeping gene, HKG, triplex (B2M, UBC and UCE). The laboratories used different chemistries and instrumentation. All laboratories were able to successfully isolate and detect mRNA in contact traces (e.g., human skin, palm-, hand- and fingerprints, clothing, car interiors, computer accessories and electronic devices). The simultaneous extraction of RNA and DNA provides an opportunity for positive identification of the tissue source of origin by mRNA profiling as well as a simultaneous identification of the body fluid donor by STR profiling. The skin markers LCE1C and LOR and the housekeeping gene marker B2M were detected in the majority of contact traces. Detection of the other markers was inconsistent, possibly due to the low amounts and/or poor quality of the genetic material present in shed skin cells. The results of this and the previous collaborative RNA exercises support RNA profiling as a reliable body fluid/tissue identification method that can easily be combined with current STR typing technology.

Neopterin release by myeloid leukaemic cells can be synergistically augmented by 1,25-dihydroxyvitamin D3 in combination with gamma interferon or granulocyte-macrophage colony stimulating factor.

Neopterin is a pteridine molecule released by immune activated monocytes. Monocytic maturation may be induced in acute myeloid leukaemia (AML) blasts and the U937 leukaemic cell line by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], an effect which is augmented by both gamma interferon (IFN) or granulocyte-macrophage colony stimulating factor (GM-CSF). We have demonstrated that, while 1,25(OH)2D3 and GM-CSF alone have little effect, both IFN and GM-CSF act synergistically with 1,25(OH)2D3 to increase neopterin secretion in the U937 cell line. Neopterin secretion was associated with, but not necessarily dependent on, the degree of phenotypic differentiation achieved by cells. Neopterin secretion was also synergistically enhanced in AML blasts by the action of 1,25(OH)2D3 in combination with IFN but not GM-CSF; secretion was enhanced in AML blasts without concomitant evidence of phenotypic maturation. We have shown that the monocytoid cell line U937, under appropriate conditions, may secrete neopterin in response to stimulatory agents other than IFN. In addition, the distinct difference in the pattern of response to the combination of 1,25(OH)2D3 with GM-CSF compared with that of 1,25(OH)2D3 plus IFN suggests that the augmentation of 1,25(OH)2D3 effect by IFN and GM-CSF is mediated by separate mechanisms.

Circulating MMP9, vitamin D and variation in the TIMP-1 response with VDR genotype: mechanisms for inflammatory damage in chronic disorders?

BACKGROUND: Vitamin-D deficiency and vitamin-D receptor genotype (VDR) are risk factors for several disorders with inflammatory components, including coronary heart disease (CHD) and diabetes, though the mechanisms involved are unclear. AIM: To examine the hypothesis that vitamin D status modulates the matrix metalloproteinase (MMP) system in a population with a high prevalence of vitamin D deficiency, a situation affecting susceptibility to CHD and diabetes. DESIGN: Prospective cross-sectional, interventional and embedded studies. METHODS: Circulating MMP2,9, the inhibitor TIMP-1 and C-reactive protein (CRP) were measured during studies of vitamin-D deficiency as a risk factor for type 2 diabetes and CHD in 171 healthy British Bangladeshi adults, free of known diabetes or major illness. Vitamin D status, VDR genotype, body-build, blood pressure, lipid and insulin profiles, glucose tolerance, fibrinogen, PAI-1, folate and homocysteine were measured. Vitamin-D-deficient subjects were re-assessed after 1 years' supplementation. MMP, TIMP-1 and CRP levels were measured in 41 subjects halfway through 5-year follow-up. Independent determinants of circulating concentrations of MMP9, TIMP-1 and CRP were assessed by multiple regression analysis. RESULTS: Vitamin D status was the sole determinant of circulating MMP9 (inversely) and an independent determinant of CRP (inversely). Determinants of TIMP-1 were MMP9, systolic blood-pressure (directly) and VDR genotype (TaqI). Significant reductions in MMP9 (-68%), TIMP-1 (-38%) and CRP (-23%) concentrations followed vitamin-D supplementation. DISCUSSION: Vitamin-D insufficiency is associated with increased circulating MMP2,9 and CRP, correctable by supplementation. This finding provides a possible mechanism for tissue damage in chronic inflammatory conditions, including CHD and diabetes.

Recombinant alpha 2B interferon in combination with oral chemotherapy in late chronic phase chronic myeloid leukaemia.

The place of alpha interferon (IFN) therapy in the treatment of chronic myeloid leukaemia (CML) is under intensive investigation at present. It is now established that as a single agent it can provide good disease control in the chronic phase and that cytogenetic responses will occur in a minority of patients. However its impact on long term survival has been less certain. Optimal haematological and cytogenetic results have to date been seen when IFN is used in the early phase of the disease, i.e. within one year of diagnosis. We have performed a prospective single arm study on the effect on survival of the addition of low dose IFN (9 mU/week) to conventional oral chemotherapy in patients who were at a median of 19 months from the initial diagnosis at the time of study entry. Comparison of this cohort with a control group of CML patients treated with oral chemotherapy only at the same participating institutions gave an estimated 72% reduction in the risk of death as a result of IFN therapy. Median survival for the IFN group has not been reached at 43 months compared with a median survival of 33 months for the chemotherapy alone group. These results suggest that the introduction of low dose IFN at any stage in the chronic phase may produce a worthwhile improvement in survival.

Angiographic restenosis after angioplasty: comparison of definitions and correlation with clinical outcome.

BACKGROUND: The aim of this study was to assess which of the currently used definitions of restenosis most closely indicates degree of recurrence and clinical status by 1) correlating percentage luminal renarrowing with restenosis defined according to each of four definitions, and 2) evaluating which definition was best predicted by clinical recurrence. METHODS: Quantitative angiography in 125 patients was undertaken either at time of early clinical presentation or at 6-month follow-up after percutaneous transluminal coronary angioplasty (PTCA). Absolute luminal diameters measured before and after PTCA and at follow-up were plotted as the percentage return from post-PTCA toward pre-PTCA value. All patients were also defined as restenosed or not restenosed according to each of the four definitions. RESULTS: The angiographic restenosis rate varied from 31% to 47%. Other than for "loss of 50% absolute gain," all definitions defined restenosis in some patients, despite the degree of return from post-PTCA to pre-PTCA value being less than 50%. Early recurrent symptoms predicted angiographic restenosis best, irrespective of angiographic definition, whereas history of recurrent angina or positive exercise testing alone at follow-up were poor predictors (range, 0.46 to 0.54). The predictive value increased (0.75 to 0.87) when exercise testing was positive in patients complaining of angina. The definition "loss of 2 standard deviations" gave the lowest values for positive or negative predictive values irrespective of clinical parameter. CONCLUSIONS: "Loss of 50% absolute gain" may be the best compromise definition. Patients admitted early with angina should undergo recatheterization, whereas exercise tests should be reserved for patients who complain of angina at routine follow-up.

Young infarct patients with single-vessel occlusion do not have an underlying prothrombotic state to explain their coronary occlusion.

To determine the importance of a prothrombotic state in the pathogenesis of coronary occlusion in young infarct patients, assessment of risk factor profile and thrombotic tendency was undertaken in 25 young male patients (age less than 45 yr) who were shown at angiography, following myocardial infarction, to have occlusion of a single coronary. Comparison was made with a control group of symptomatic males aged greater than 55 yr, who at angiography had significant disease in two or more coronary arteries (multi-vessel disease control group). At the time of the study more patients in the single-vessel disease study group smoked cigarettes (n = 12) compared to the control group (n = 5) (p less than 0.01). Serum cholesterol and triglycerides were higher, and high density lipoprotein-cholesterol lower, in the single-vessel disease group but the difference reached significance only with the high density lipoprotein-cholesterol. Quantitative platelet aggregability was similar in the two groups. Although the level of beta-thromboglobulin, was higher in the single-vessel disease study group the difference was not significant. There were also no significant differences between these groups in levels of fibrinogen, Factor XII and alpha-2 antiplasmin. Patients in the multi-vessel disease group, however, had increased Factor VII levels (p less than 0.01). There were no significant differences between the two groups in fibrinolytic potential or in levels of antithrombin III. Coronary occlusion in the young appears likely to be due primarily to an arterial (plaque) related event as opposed to an abnormal coagulation response to minor arterial plaque damage.

Results of collaborative study regarding the standardization of the Y-linked STR system DYS385 by the European DNA Profiling (EDNAP) group.

Y-chromosome linked short tandem repeat (STR) loci are inherited as a closely linked haplotype, which appears to remain stable in a given paternal lineage over many generations. In forensic cases, Y-linked STRs are particularly useful for the identification of human remains as well as in rape cases with mixed male/female stain samples. DYS385 is derived from tandemly duplicated segments of the Y chromosome thus giving rise to two fragments of variable length which do not behave like alleles but genotypes. The European DNA Profiling (EDNAP) group has carried out a collaborative exercise among 14 participating laboratories using DYS385 for typing of five unknown bloodstains and a control sample. Furthermore, population data from eight different European countries with samples sizes between 91 and 150 male individuals were collected. The results confirm previous observations that DYS385 is one of the most informative Y-linked STR loci. It could also be demonstrated that reproducible results can be obtained independently from the electrophoretic separation and detection methods used. Thus DYS385 may serve as a useful complementation to the routinely used autosomal STR systems in special cases.

Band shift analysis of three base-pair repeat alleles in the short tandem repeat locus D12S391.

Two hundred and sixty UK Caucasian individuals have been typed for the STR locus D12S391. Measurements of absolute band shift, relative to an allelic ladder, allowed fragments differing by one base pair to be consistently distinguished. The intermediate alleles typed from such fragments comprised approximately 5% of the total alleles observed in this study. The existence of intermediate alleles in the D12S391 locus, not included in the allelic ladder, allowed us to assess the efficacy of band shift analysis in detecting intermediate alleles on two different automated fluorescent detection platforms. The results of sequencing a sample of intermediate alleles are also presented.

Investigation of the between-gel and within-gel variation in fragment size determinations found when using single locus DNA probes.

Measurement variation in the sizing of DNA fragments has been assessed, examining within-gel and between-gel variability. Also, measurement variation detected between two different laboratories, using both manual and automated measurement techniques, has been investigated and discussed.