Implementing a biogeographic ancestry inference service for forensic casework.

The Centre of Forensic Sciences has validated the Precision ID Ancestry Panel on the Ion S5™ Massively Parallel Sequencing instrument for use in forensic casework. The focus of this paper is the development of reporting guidelines for implementation of the biogeographic ancestry inference service based on the Admixture Prediction results produced using the Torrent Suite™ Software (Thermo Fisher Scientific). The Admixture Prediction algorithm estimates the genetic ancestry of a sample using seven root populations (Europe, East Asia, Oceania, America, Africa, South Asia, and Southwest Asia). For individuals that declared a single ancestry, there was a high correlation between the declared ancestry and the ancestry predicted by the algorithm. However, some individuals with declared ancestries of Southern Europe, Southwest Asia, South Asia and Horn of Africa had Admixture Predictions that were composed of two or more root populations at 20% or greater. For individuals with known admixed ancestry, the major component of their declaration was included in their results in all but one case. Based on these results, reporting guidelines were developed and subsequently evaluated using the Admixture Predictions of additional samples. This paper discusses the development and evaluation of these reporting guidelines, along with an implementation plan for forensic casework.

Inferring the presence of spermatozoa in forensic samples based on male DNA fractionation following differential extraction.

To address sexual assault kit backlogs some laboratories in North America have implemented 'Direct to DNA' (DTD) approaches for the examination of relevant vaginal, oral, rectal and external genitalia swabs from sexual assault examination kits. Using this approach no preliminary serological screening for semen or spermatozoa is performed. Instead, swabs are directly subjected to differential extraction and quantitation using a dual quantification system. Decisions regarding the next steps in processing each sample are typically based on the quantity of male DNA detected, the fraction in which it is detected, and its ratio to the total human DNA in the sample. In the absence of serological results it remains of value in many cases to determine whether spermatozoa are present in the sample and whether the male DNA profile may be attributed to this body fluid. In this study we examine the distribution of male DNA from various body fluids between epithelial and spermatozoa fractions following differential extraction. Based on these results we identified criteria under which a DNA profile can be reliably attributed to spermatozoa. A total of 18 blood samples, 129 saliva samples, and 78 semen samples were processed. The maximum amount of male DNA observed in the sperm fraction of a spermatozoa-free sample was 10.4 ng and the maximum portion of total male DNA observed in the sperm fraction was 7.7%. In contrast, when a sample contained spermatozoa the minimum portion of total male DNA observed in the sperm fraction was 52.6%. This research supports a 50% threshold of male DNA in the sperm fraction following differential extraction as a conservative criterion under which the scientist at the Centre of Forensic Sciences (CFS) may infer that spermatozoa is present in a sample in the absence of serological results. This general threshold is applicable to all sample types (underwear, clothing, swabs, condoms) tested. We further demonstrate that, if the same male DNA profile is represented more prominently in the sperm fraction versus the epithelial fraction, the analyst should not fall into the intuitive trap of inferring the presence of spermatozoa in the sample. Instead, enrichment calculations must be based on the measured quantity of male and total DNA in each fraction and not the male:female DNA ratios observed in the DNA profiles.

Can a normal range of elbow movement predict a normal elbow x ray?

BACKGROUND: Elbow injuries account for approximately 2-3% of presentations to the emergency department. This is associated not only with a very high rate of x rays but also with a very high rate of "missed fractures" This study examines which components of elbow examination have the best correlation with a normal radiograph. DESIGN SETTING: A district general hospital's emergency department seeing 83,000 new attendances per annum (pa) (approximately 1600 elbow injuries pa). METHODS: After estimating the power before data collection, all patients presenting with elbow injuries were considered for inclusion, and were excluded only if they were unable to follow instructions owing to either reduced conscious levels or mental conditions. A proforma was completed after patient examination, indicating the features of clinical examination, and the results of radiographs if any. The formal report of all radiographs taken was sought from the radiology department. RESULTS: 407 patients were entered into the study, of whom 331 received a radiograph of the elbow. Full extension of the elbow had a specificity of 0.916 (95% confidence interval (CI) 0.863 to 0.969, sensitivity 0.478) for detection of a normal radiograph. An equal range of movement ROM had a specificity of 0.976 (95% CI 0.940 to 0.991, sensitivity 0.211). Subgroup analysis of patients aged < 16 years showed a specificity of equal ROM of 1 (95% CI 0.941 to 1.000) for the detection of a normal x ray. Logistic regression analysis showed that best predictive values were achieved by a combination of full extension, flexion and supination. CONCLUSION: A two-tier clinical rule for management of elbow injury is proposed: (1) Those patients aged < or = 16 years with a ROM equal to the unaffected side may be safely discharged; (2) Those patients with normal extension, flexion and supination do not require emergent elbow radiographs.