An analysis of data curated from 5 years of identifying human remains.

An archive of 5 years of cases involving the identification of human remains was curated, collecting information on: The sample type submitted, the number of STR loci yielding interpretable results, the kinship challenge posed, and the outcome for the case. A total of 129 cases of remains ID were investigated using manual DNA extraction and recovery methods with amplification of STR markers using the Power Plex 21 multiplex STR kit from Promega Corp. In 52 cases, blood spots collected by the ME were provided as sample and in 100% of those cases, probabilities of relatedness to the reference samples was ≥99%. In 77 cases, tissue other than blood was provided as a source of DNA. These other samples were grouped categorically into long bones (femur and tibia; 40 cases), skull bones/teeth (11 cases), other bones (16 cases), and tissue (normally adherent to bone) (10 cases). Reference samples provided for cases included alleged parents or child(ren) of the victim (86 cases), alleged full siblings of the victim (38 cases), or alleged second-order relatives (five cases). The overall success rate in confirming the identity of the source of the remains in these cases was 89.2%. Our results demonstrate that a laboratory can be often successful identifying human remains using methods easily implemented in any DNA typing laboratory.

Deep sleep and beeps II: Sleep quality improvement project in general surgery patients.

BACKGROUND: Poor sleep leads to poor health outcomes. Phase I of our sleep quality improvement project showed severe sleep disturbance in the ward setting. We implemented a novel PostOp Pack to improve sleep quality. METHODS: Patients underwent elective, general surgery procedures. Fitbit trackers measured total sleep time. Patients completed the inpatient Richards-Campbell Sleep Questionnaire, which combines 5 domains into a cumulative score (0-100). Patients completed the outpatient Pittsburgh Sleep Quality Index preoperatively and postoperatively. Patients received the PostOp Pack, which included physical items and a sleep-protective order set to reduce nighttime awakenings. Patients from phase I served as the historical control. The primary outcome was the percentage of patients with Richards-Campbell Sleep Questionnaire total sleep score ≥50. The secondary outcomes included the mean Richards-Campbell Sleep Questionnaire domain scores and Fitbit total sleep time. RESULTS: A total of 49 patients were compared with 64 historical controls. The percentage of patients with a total sleep score ≥50 was significantly higher in patients receiving a PostOp Pack versus historical control (69% vs. 44%, difference 26%, 95% confidence interval 6.1-45%, P = .01). The mean Richards-Campbell Sleep Questionnaire Total Sleep Score was significantly higher in patients with a PostOp Pack (62 vs 49, mean difference 13, 95% confidence interval 6-21, P ≤ .01). The PostOp Pack Richards-Campbell Sleep Questionnaire domain scores were significantly higher in various areas: Sleep Latency (68 vs 49, P ≤ .01), Awakenings (56 vs 40, P = .01), Sleep Quality (61 vs 49, P = .02), and Noise Disturbance (70 vs 59, P = .04). Of all patients, 92% would use PostOp Pack again in a future hospitalization. No patients had a failure to rescue event with PostOp Pack. The mean total sleep time was significantly improved with PostOp Pack on night 1 (6.4 vs 4.7 hours, P = .03). CONCLUSION: The PostOp Pack improves inpatient sleep quality and is safe.

Deep Sleep and Beeps: Sleep Quality Improvement Project in General Surgery Patients.

BACKGROUND: Poor sleep leads to poor health outcomes. Inpatient sleep disturbance has been studied primarily in the ICU. Minimal research exists on sleep in surgical populations. METHODS: We recruited patients undergoing elective, inpatient general surgery procedures. Participants wore Fitbit trackers while inpatient to measure total sleep time (CDC recommendation is 7 or more hours per night). At discharge, patients completed the Richards-Campbell Sleep Questionnaire (RCSQ) to measure inpatient sleep quality. The RCSQ combines 5 domains into a cumulative score (0 to 100); a higher score means better sleep quality. Patients also completed the outpatient Pittsburgh Sleep Quality Index preoperatively and postoperatively. The primary end point was percentage of patients with total sleep score ≥ 50. Secondary outcomes included mean RCSQ domain scores, Fitbit total sleep time, and percentage with Pittsburgh Sleep Quality Index Score indicating poor sleep. RESULTS: We included 64 patients (mean ± SD age 55.0 ± 14.1 years). Mean ± SD RCSQ total sleep score was 49 ± 20.5 and 53.1% with total sleep score < 50. Mean ± SD RCSQ domain scores were Awakenings: 40.4 ± 22.8, Sleep Quality: 49.1 ± 27.9, Sleep Latency: 49.2 ± 25.3, Sleep Depth: 50.2 ± 26.5, Returning to Sleep: 55.9 ± 28.1, and Noise Disturbance: 59.1 ± 27.9. On night one, 25 devices (40%) had recorded sleep data due to enough sleep. Mean ± SD total sleep time on night 1 was 4.7 ± 2.8 hours. Mean total sleep time for nights 2, 3, and 4 remained fewer than 7 hours. Percentages for each night that achieved the CDC goal of 7 or more hours were as follows: night one 10.9%, night two 32.8%, night three 35.3%, and night four 27.6%. Per the Pittsburgh Sleep Quality Index, 88.1% of patients were poor sleepers preoperatively and 84.5% were poor sleepers at follow-up (p = 0.6). CONCLUSIONS: Elective general surgery patients experience a severe inpatient sleep disturbance, worse than in similarly studied ICU cohorts. This disturbance is driven primarily by nighttime awakenings.

The effect of environmental conditions on the rate of RNA degradation in dried blood stains.

The relationship between RNA degradation and the age of a bloodstain has been suggested by the work of several investigators. A prior study from this laboratory described a qPCR assay that was effective at estimating the age of bloodstains stored in an environmentally controlled laboratory for periods of up to one year. In this study, the effect of the environmental conditions on the rate of RNA degradation during storage was analyzed. Bloodstains were prepared on stain cards and stored in one of 9 different environments for periods of up to 24 weeks. At selected times during the storage term, RNA was extracted, reverse transcribed, and the integrity of select transcripts analyzed. Three temperatures (37 °C, 20 °C, and 4 °C) and three relative humidities (rH) (75 %, 35 %, and 10 %) were combined pairwise. The rate of RNA degradation was found to increase 5-10 fold in stains stored at 37 °C versus those stored at 20 °C. The rate of RNA degradation was faster for stains stored at 20 °C compared to 4 °C but differed only 2-4 fold. Multivariate regression analysis suggests elevations in temperature or rH will accelerate RNA degradation and will do so to a similar extent. It is clear from the data that the integrity of the transcriptome in dried bloodstains is better preserved in a cold and dry environment. Investigations are ongoing to develop an approach for the estimation of sample age that incorporates the environmental conditions of a crime scene into the age estimate.

Simulating the effects of operating room staff movement and door opening policies on microbial load.

OBJECTIVE: To identify factors that increase the microbial load in the operating room (OR) and recommend solutions to minimize the effect of these factors. DESIGN: Observation and sampling study. SETTING: Academic health center, public hospitals. METHODS: We analyzed 4 videotaped orthopedic surgeries (15 hours in total) for door openings and staff movement. The data were translated into a script denoting a representative frequency and location of movements for each OR team member. These activities were then simulated for 30 minutes per trial in a functional operating room by the researchers re-enacting OR staff-member roles, while collecting bacteria and fungi using settle plates. To test the hypotheses on the influence of activity on microbial load, an experimental design was created in which each factor was tested at higher (and lower) than normal activity settings for a 30-minute period. These trials were conducted in 2 phases. RESULTS: The frequency of door opening did not independently affect the microbial load in the OR. However, a longer duration and greater width of door opening led to increased microbial load in the OR. Increased staff movement also increased the microbial load. There was a significantly higher microbial load on the floor than at waist level. CONCLUSIONS: Movement of staff and the duration and width of door opening definitely affects the OR microbial load. However, further investigation is needed to determine how the number of staff affects the microbial load and how to reduce the microbial load at the surgical table.

Author Correction: Variable water input controls evolution of the Lesser Antilles volcanic arc.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Variable water input controls evolution of the Lesser Antilles volcanic arc.

Oceanic lithosphere carries volatiles, notably water, into the mantle through subduction at convergent plate boundaries. This subducted water exercises control on the production of magma, earthquakes, formation of continental crust and mineral resources. Identifying different potential fluid sources (sediments, crust and mantle lithosphere) and tracing fluids from their release to the surface has proved challenging1. Atlantic subduction zones are a valuable endmember when studying this deep water cycle because hydration in Atlantic lithosphere, produced by slow spreading, is expected to be highly non-uniform2. Here, as part of a multi-disciplinary project in the Lesser Antilles volcanic arc3, we studied boron trace element and isotopic fingerprints of melt inclusions. These reveal that serpentine-that is, hydrated mantle rather than crust or sediments-is a dominant supplier of subducted water to the central arc. This serpentine is most likely to reside in a set of major fracture zones subducted beneath the central arc over approximately the past ten million years. The current dehydration of these fracture zones coincides with the current locations of the highest rates of earthquakes and prominent low shear velocities, whereas the preceding history of dehydration is consistent with the locations of higher volcanic productivity and thicker arc crust. These combined geochemical and geophysical data indicate that the structure and hydration of the subducted plate are directly connected to the evolution of the arc and its associated seismic and volcanic hazards.

Reimagining Ambulatory Care as a Key to Population Health.

SUMMARY: Ambulatory care is a key to achieving better population health-not traditional ambulatory (outpatient) care, but rather ambulatory care reimagined. Ambulatory care is so vital that we at Intermountain Healthcare redesigned our entire organization to prioritize it and give it the attention it deserves.Historically, outpatient care was a point of access that connected many patients with specialty care, where hospitals made their money. Doctors in private practices referred their patients to the hospitals with which they were affiliated, and that arrangement provided the hospitals with a stream of patients on which they relied financially. Today, ambulatory care plays an entirely different role in the context of population health. Healthcare providers are paid a flat fee per person and gain a benefit when people stay healthy. In this new context, ambulatory care is a mechanism to get ahead of health problems and avoid more extensive treatments.This change then begs a question: How do healthcare providers support their essential services if ambulatory care is working to reduce the stream of patients to hospitals? The answer has three parts, and it is the reason we redesigned Intermountain Healthcare and began to roll out a series of new products and initiatives to implement that redesign.

First Case On-Time Starts Measured by Incision On-Time and No Grace Period: A Case Study of Operating Room Management.

EXECUTIVE SUMMARY: A delay in first case on-time starts (FCOTS) can lead to less operating room (OR) utilization, greater facility costs, and dissatisfaction among staff and patients. FCOTS is usually measured by the patient in-room metric with a small grace period. For this study, the partnering hospital elected to target and improve delays by aggressively defining FCOTS as time of incision with no grace period. Metric standardization, goal setting, and organizational focus contributed to a 9-month implementation plan to improve the newly defined FCOTS metric. The target was achieved during implementation, with 73.6% of first cases starting on time. Annual impact showed 80,587 min, or 1,343 hr, of saved OR time, which led to $771,000 in annual savings for variable OR labor costs. This redefined metric and related interventions contributed to significant reduction in delays and savings to the hospital. Engaged physician leadership played a key role in this improvement initiative, as well. The methods employed here can be used in other hospitals looking to improve FCOTS metrics in their procedural areas.

A method to estimate the age of bloodstains using quantitative PCR.

The value of RNA analysis in the forensic laboratory as one means of identifying the nature of biological evidence of forensic relevance has been well established. The degradation of RNA in dried body fluid stains has also been an area of forensic interest because of the potential to estimate the age of a stain recovered from a crime scene. Here we describe a qPCR assay that demonstrates it is possible to estimate the age of bloodstains with reasonable accuracy. The 5'-3' qPCR assay exploits the observation the 5' end of an mRNA transcript degrades in dried stains faster than the 3' end. This differential degradation pattern can be followed with a qPCR assay that quantifies ∼90 bp amplicons produced from the 5' and 3' ends of 4 transcripts chosen from the transcriptome of blood because of their degradation kinetics, determined initially using RNA sequencing. Statistical analysis of degradation kinetics suggests, depending upon the age of the sample, the age of blood stains can be accurately estimated to within 2-4 weeks for stains less than 6 months of age and 4-6 weeks for stains 6 months to 1 year old.

Evaluation of degradation in DNA from males with a quantitative gender typing, endpoint PCR multiplex.

Evidentiary samples submitted to a forensic DNA laboratory occasionally yield DNA that is degraded. Samples of intact chromosomal DNA (both nuclear and mitochondrial) were subjected to a heating protocol to induce DNA degradation. The DNAs were then analyzed using a multiplex PCR assay that amplifies targets of low and high molecular weight on the X/Y and mitochondrial chromosomes. If degradation is random, the amplification of larger DNA targets should be more adversely affected by degradation than smaller targets. In nuclear and mitochondrial DNA from a male donor, exhibiting degradation, DNA quantity estimates based upon higher molecular weight amplicons (HMW) are significantly lower than estimates made using low molecular weight (LMW) Q-TAT amplicons. DNA degradation estimated using this approach correlated well with actual fluorescence associated with HMW and LMW STR alleles amplified from the same genomic DNA templates. Q-TAT is thus useful not only as a quantitation tool, but also as an indicator of template degradation.

Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis.

PURPOSE: Cinnamon has been studied in randomized controlled trials (RCTs) for its glycemic-lowering effects, but studies have been small and show conflicting results. A prior meta-analysis did not show significant results, but several RCTs have been published since then. We conducted an updated systematic review and meta-analysis of RCTs evaluating cinnamon's effect on glycemia and lipid levels. METHODS: MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched through February 2012. Included RCTs evaluated cinnamon compared with control in patients with type 2 diabetes and reported at least one of the following: glycated hemoglobin (A1c), fasting plasma glucose, total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), or triglycerides. Weighted mean differences (with 95% confidence intervals) for endpoints were calculated using random-effects models. RESULTS: In a meta-analysis of 10 RCTs (n = 543 patients), cinnamon doses of 120 mg/d to 6 g/d for 4 to 18 weeks reduced levels of fasting plasma glucose (-24.59 mg/dL; 95% CI, -40.52 to -8.67 mg/dL), total cholesterol (-15.60 mg/dL; 95% CI, -29.76 to -1.44 mg/dL), LDL-C (-9.42 mg/dL; 95% CI, -17.21 to -1.63 mg/dL), and triglycerides (-29.59 mg/dL; 95% CI, -48.27 to -10.91 mg/dL). Cinnamon also increased levels of HDL-C (1.66 mg/dL; 95% CI, 1.09 to 2.24 mg/dL). No significant effect on hemoglobin A1c levels (-0.16%; 95%, CI -0.39% to 0.02%) was seen. High degrees of heterogeneity were present for all analyses except HDL-C (I(2) ranging from 66.5% to 94.72%). CONCLUSIONS: The consumption of cinnamon is associated with a statistically significant decrease in levels of fasting plasma glucose, total cholesterol, LDL-C, and triglyceride levels, and an increase in HDL-C levels; however, no significant effect on hemoglobin A1c was found. The high degree of heterogeneity may limit the ability to apply these results to patient care, because the preferred dose and duration of therapy are unclear.

Diagnostic accuracy of rectal mucosa biopsy testing for chronic wasting disease within white-tailed deer (Odocoileus virginianus) herds in North America: effects of age, sex, polymorphism at PRNP codon 96, and disease progression.

An effective live animal diagnostic test is needed to assist in the control of chronic wasting disease (CWD), which has spread through captive and wild herds of white-tailed deer (Odocoileus virginianus) in Canada and the United States. In the present study, the diagnostic accuracy of rectal mucosa biopsy sample testing was determined in white-tailed deer from 4 CWD-infected captive herds. Specifically, the current study compared the immunohistochemical detection of disease-associated prion protein in postmortem rectal mucosa biopsy samples to the CWD status of each deer as determined by immunodiagnostic evaluations of the brainstem at the obex, the medial retropharyngeal lymph node, and the palatine tonsil. The effects of age, sex, genotype, and disease progression were also evaluated. Diagnostic sensitivity on rectal biopsy samples for CWD in white-tailed deer ranged from 63% to 100%; the pooled estimate of sensitivity was 68% with 95% confidence limits (95% CLs) of 49% and 82%. However, diagnostic sensitivity was dependent on genotype at prion protein gene (PRNP) codon 96 and on disease progression as assessed by obex grade. Diagnostic sensitivity was 76% (95% CLs: 49%, 91%) for 96GG deer but only 42% (95% CLs: 13%, 79%) for 96GS deer. Furthermore, diagnostic sensitivity was only 36% for deer in the earliest stage of disease (obex grade 0) but was 100% for deer in the last 2 stages of preclinical disease (obex grades 3 and 4). The overall diagnostic specificity was 99.8%. Selective use of antemortem rectal biopsy sample testing would provide valuable information during disease investigations of CWD-suspect deer herds.

Method: a single nucleotide polymorphism genotyping method for Wheat streak mosaic virus.

BACKGROUND: The September 11, 2001 attacks on the World Trade Center and the Pentagon increased the concern about the potential for terrorist attacks on many vulnerable sectors of the US, including agriculture. The concentrated nature of crops, easily obtainable biological agents, and highly detrimental impacts make agroterrorism a potential threat. Although procedures for an effective criminal investigation and attribution following such an attack are available, important enhancements are still needed, one of which is the capability for fine discrimination among pathogen strains. The purpose of this study was to develop a molecular typing assay for use in a forensic investigation, using Wheat streak mosaic virus (WSMV) as a model plant virus. METHOD: This genotyping technique utilizes single base primer extension to generate a genetic fingerprint. Fifteen single nucleotide polymorphisms (SNPs) within the coat protein and helper component-protease genes were selected as the genetic markers for this assay. Assay optimization and sensitivity testing was conducted using synthetic targets. WSMV strains and field isolates were collected from regions around the world and used to evaluate the assay for discrimination. The assay specificity was tested against a panel of near-neighbors consisting of genetic and environmental near-neighbors. RESULT: Each WSMV strain or field isolate tested produced a unique SNP fingerprint, with the exception of three isolates collected within the same geographic location that produced indistinguishable fingerprints. The results were consistent among replicates, demonstrating the reproducibility of the assay. No SNP fingerprints were generated from organisms included in the near-neighbor panel, suggesting the assay is specific for WSMV. Using synthetic targets, a complete profile could be generated from as low as 7.15 fmoles of cDNA. CONCLUSION: The molecular typing method presented is one tool that could be incorporated into the forensic science tool box after a thorough validation study. This method incorporates molecular biology techniques that are already well established in research and diagnostic laboratories, allowing for an easy introduction of this method into existing laboratories. KEYWORDS: single nucleotide polymorphisms, genotyping, plant pathology, viruses, microbial forensics, Single base primer extension, SNaPshot Multiplex Kit.

Molecular assay for screening and quantifying DNA in biological evidence: the modified Q-TAT assay.

A method is described for the quantitation of total human and male DNA. Q-TAT utilizes end-point, multiplex polymerase chain reaction (PCR) amplification of the amelogenin and SRY loci to quantify DNA and incorporates a cloned nonhuman template to detect PCR inhibition. Standard curves of fluorescence from amelogenin or SRY amplicons were generated from amplification of known amounts of NIST traceable SRM-female or SRM-male DNA. Curves showed good linearity up to 500 pg of SRM-template (R(2) > 0.99) and reliably estimated total and male DNA content in casework samples. The nonhuman pRL(null) template included in each PCR was a sensitive indicator of known PCR inhibitors including EDTA, hemin, blue denim dye, and humic acid. Finally, the SRY amplicon was a sensitive indicator of male DNA and, in mixtures, could reliably estimate male DNA present in an excess of female DNA. The Q-TAT multiplex is a reliable quantitation method for forensic DNA typing.

Population data for 15 STR loci (Identifiler kit) in a Filipino population.

Allele frequencies for fifteen STR loci, D3S1358, TH01, D21S11, D18S51, D2S1338, D5S818, D13S317, D7S820, D16S539, CSF1PO, D19S433, vWA, D8S1179, TPOX and FGA, were investigated in a Filipino ethnic group resident in the United States and in the Philippines. Statistical evaluation of the data collected indicated the population to be in Hardy-Weinberg equilibrium and therefore acceptable for calculations in forensic and family relatedness casework.

Considerations for the interpretation of STR results in cases of questioned half-sibship.

Likelihood ratios (LRs) were calculated for a cohort of 60 pairs of true half-sibs and compared with LR values calculated for unrelated, paired children. STR results for the half-sib group were obtained from 60 archived cases involving a true mother, two children, and an alleged father subjected to typing with a multiplex STR kit (Identifiler multiplex, Applied Biosystems) and in which the alleged father was excluded as the father of only one of the two children (half-sib pairs). The distribution of LR values among true half-sibs was compared to those produced from paired, unrelated children selected in two ways: One method for producing unrelated pairs was to randomly select Identifiler profiles from children in 120 distinct paternity cases and group them into 60 ethnically matched pairs (random pairs). In a second approach, the children in the true half-sib group were shuffled and ultimately paired with someone from a different case. A total of 49 ethnically matched, unrelated pairs were created (shuffled pairs). In the shuffled pairs group, comparisons were thus based on a constant set of phenotypes. LRs comparing the probability of half-sibship versus being unrelated were produced for all groups with standard methods. Among pairs of known half-sibs, LRs ranged from a low of 0.1 to a maximum of 3763. Among random and shuffled pairs, LRs ranged from a low of 0.0001 to 12 for shuffled pairs or 42 for random pairs. LRs of greater than 2 were produced in 8 instances among random pairs and in 4 instances among the shuffled pairs. Overall, results suggest that half-sib indices of 30 or greater are fairly characteristic of individuals who are related as half-sibs. In contrast, half-sib indices of 0.1 or less are fairly characteristic of unrelated individuals who claim to be half-sibs. LRs falling between 0.1 and 10.0 are uninformative, as this region represents the overlap in the LR distributions produced from the true and false half-sib groups when the Identifiler multiplex kit is used for testing.

Quantitation of human genomic DNA through amplification of the amelogenin locus.

An alternate method for quantitation of human genomic DNA is presented. Quantitative template amplification technology (abbreviated "Q-TAT") estimates the quantity of human DNA present in an extract by comparing fluorescence in X and Y amplicons produced from unknowns with fluorescence in a standard curve amplified from known quantities of reference DNA. Q-TAT utilizes PCR and electrophoresis with fluorescent detection/quantitation, precluding the need for new instrumentation, methodology, or quality assurance associated with slot-blot or real-time PCR. In a comparison study incorporating shared samples, Q-TAT was found to be more sensitive than widely used slot-blot methods but somewhat less sensitive than real-time PCR. Among samples containing DNA concentrations ranging from 100 pg/microL to 2-4 ng/microL, Q-TAT produced DNA concentration estimates that agreed reasonably well with either Quantiblot or real-time PCR. Q-TAT was reproducible with a typical coincidence of variation of about 35%. Quantitation of human DNA in this study involved summing fluorescence in X and Y amplicons in unknowns and quantitation standards. However, analyzing fluorescence in X and Y amplicons individually could allow estimates of male and female DNA present in mixtures to be made. Moreover, since X and Y amplicons exhibit sizes of 210 and 216 bp, respectively, the integrity as well as the concentration of the genomic DNA template can be assessed. Q-TAT represents an alternate method useful for the quantitation of human genomic DNA prior to amplification of STR loci used for identity testing purposes. The method uses existing equipment and procedures in conjunction with a well-characterized DNA standard to produce concentration estimates for unknowns that reliably produce STR profiles suitable for analysis.

Resolution of a serum sample mix-up through the use of short tandem repeat DNA typing.

BACKGROUND: A sample mix-up occurred in a tissue procurement laboratory in which aliquots of serum from two tissue donors were accidentally mislabeled. The clues to the apparent mixup involved discrepant Hepatitis C test results. In an attempt to resolve the apparent mix up, DNA typing was performed using serum samples as a possible source of genomic DNA. STUDY DESIGN AND METHODS: Two hundred microliter aliquots of two reference sera and aliquots prepared from them were subjected to DNA extraction. PCR amplification of 9 STR loci was performed on the extracts and amplicons were analyzed by capillary electrophoresis. RESULTS: About 1 microg/ml of DNA was recovered from all serum samples and was of sufficient quality to direct the amplification of most, if not all STR loci allowing the mislabeled specimens to be traced to the proper tissue donor. CONCLUSIONS: Serum is a useful source of genomic DNA for STR analysis in situations in which such samples are the only source of DNA for testing. Interestingly, one of the tissue donors on life support and repeatedly receiving blood products, exhibited a mixed DNA profile indicative of the presence of DNA from multiple individuals in the bloodstream.