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1.
CMAJ Open ; 10(4): E945-E955, 2022.
Article in English | MEDLINE | ID: mdl-36319025

ABSTRACT

BACKGROUND: The Goals of Care Designation (GCD) is a medical order used to communicate the focus of a patient's care in Alberta, Canada. In this study, we aimed to determine the association between GCD type (resuscitative, medical or comfort) and resource use during hospitalization. METHODS: This was a prospective cohort study of newly hospitalized inpatients in Alberta conducted from January to September 2017. Participants were aged 55 years or older with chronic obstructive pulmonary disease, congestive heart failure, cirrhosis, cancer or renal failure; aged 55-79 years and their provider answered "no" to the "surprise question" (i.e., provider would not be surprised if the patient died in the next 6 months); or aged 80 years or older with any acute condition. The exposure of interest was GCD. The primary outcome was health care resource use during admission, measured by length of stay (LOS), intensive care unit hours, Resource Intensity Weights (RIWs), flagged interventions and palliative care referral. The secondary outcome was 30-day readmission. Adjusted regression analyses were performed (adjusted for age, sex, race and ethnicity, Clinical Frailty Scale score, comorbidities and city). RESULTS: We included 475 study participants. The median age was 83 (interquartile range 77-87) years, and 93.7% had a GCD at enrolment. Relative to patients with the resuscitative GCD type, patients with the medical GCD type had a longer LOS (1.42 times, 95% confidence interval [CI] 1.10-1.83) and a higher RIW (adjusted ratio 1.14, 95% CI 1.02-1.28). Patients with the comfort and medical GCD types had more palliative care referral (comfort GCD adjusted relative risk (RR) 9.32, 95% CI 4.32-20.08; medical GCD adjusted RR 3.58, 95% CI 1.75-7.33) but not flagged intervention use (comfort GCD adjusted RR 1.06, 95% CI 0.49-2.28; medical GCD adjusted RR 0.98, 95% CI 0.48-2.02) or 30-day readmission (comfort GCD adjusted RR 1.00, 95% CI 0.85-1.19; medical GCD adjusted RR 1.05, 95% CI 0.97-1.20). INTERPRETATION: Goals of Care Designation type early during admission was associated with LOS, RIW and palliative care referral. This suggests an alignment between health resource use and the focus of care communicated by each GCD.


Subject(s)
Critical Care , Patient Care Planning , Humans , Aged , Aged, 80 and over , Prospective Studies , Health Resources , Alberta
2.
Spine Deform ; 7(4): 588-595, 2019 07.
Article in English | MEDLINE | ID: mdl-31202376

ABSTRACT

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: This study aims to measure and describe the clinical and financial implications of the systematic implementation of intraoperative skull-femoral traction (IOSFT) and navigated sequential drilling (NSD) for posterior spinal instrumentation and fusion (PSIF) in adolescent idiopathic scoliosis (AIS) at our institution. SUMMARY OF BACKGROUND DATA: PSIF has been the standard surgical treatment for AIS. This retrospective single-center quality improvement study describes the perioperative outcomes and impact on health resource utilization following the systematic application of two classic surgical strategies modified using current technology: IOSFT and NSD. METHODS: We reviewed the medical records of 125 patients who underwent a single-stage PSIF for AIS. We identified three cohorts based on surgical strategies used intraoperatively. Traditional techniques (n = 28), IOSFT (n = 45), and IOSFT plus NSD (n = 52). The primary outcome measures were operative time, prevalence of cases requiring extended operating room time, need for blood transfusion, length of hospital stay, and cost per surgery. Secondary outcomes included implant density, degree of spine deformity correction, and perioperative complications. RESULTS: All primary outcome measures improved significantly (p < .001). Median operating time decreased by 59%. Use of late operating room hours fell from 89% to 0% and transfusion rates from 64% to 1.9%. Length of hospital stay decreased from 6 to 4 days. Comprehensive cost per case decreased by 24%. DISCUSSION: Together, IOSFT and NSD improved the quality, safety, and value of care. These surgical strategies were performed without increased perioperative complications, while reducing cost per case by 24%. CONCLUSIONS: The data presented may have significant implications in health resource utilization for AIS surgery. LEVEL OF EVIDENCE: Level III.


Subject(s)
Scoliosis/surgery , Spinal Fusion , Adolescent , Blood Transfusion/statistics & numerical data , Costs and Cost Analysis , Female , Humans , Length of Stay/statistics & numerical data , Male , Operative Time , Retrospective Studies , Spinal Fusion/adverse effects , Spinal Fusion/economics , Spinal Fusion/methods , Spinal Fusion/standards , Treatment Outcome
3.
Clin Spine Surg ; 32(10): E474-E478, 2019 12.
Article in English | MEDLINE | ID: mdl-31220037

ABSTRACT

STUDY DESIGN: This is a retrospective cohort, single-center quality improvement study. OBJECTIVES: To evaluate the effect of the intraoperative skull femoral traction (IOSFT) on sagittal balance in posterior spinal instrumentation (PSI) to manage scoliosis. SUMMARY OF BACKGROUND DATA: IOSFT has been used routinely as an adjunct technique for facilitating PSI to manage scoliosis in our institution since 2010. Previous studies have raised concerns regarding the negative effect of IOSFT on lumbar lordosis. MATERIALS AND METHODS: The medical records and radiographs of 113 patients with adolescent idiopathic scoliosis managed with single stage PSI were reviewed. Eighty-five patients were operated with IOSFT (traction group) and 28 patients were operated without traction (nontraction group). Patients who had double (anterior-posterior) approaches or nonidiopathic scoliosis were excluded. Sagittal balance and pelvic parameters at 2 years of postoperative follow-up were the primary outcome measures. Statistical analysis was done with R for statistical computing. Median values and interquartile range were compared between groups using Wilcoxon rank sum, Fischer exact, and Welch t tests. P-values of <0.05 were considered statistically significant. RESULTS: No significant differences were found comparing postoperative lumbar lordosis in the nontraction group (54 degrees) with the traction group (53 degrees) (P=0.4953). No significant differences were found in postoperative sagittal vertical axis medians comparing both groups, with 17 mm in the nontraction group and 18 mm in the traction group (P=0.3994). No significant differences were found in postoperative pelvic parameters. The median pelvic incidence was 52 degrees in the nontraction group and 50 degrees in the traction group (P=0.2711). CONCLUSIONS: According to our results, the use of IOSFT as an adjunct to facilitate PSI for managing adolescent idiopathic scoliosis had no measurable negative impact on sagittal balance in our IOSFT cohort.


Subject(s)
Femur/surgery , Intraoperative Care , Postural Balance/physiology , Scoliosis/physiopathology , Scoliosis/surgery , Skull/surgery , Traction , Adolescent , Female , Humans , Male , Outcome Assessment, Health Care , Postoperative Complications/etiology
4.
Cancer Res ; 79(3): 467-481, 2019 02 01.
Article in English | MEDLINE | ID: mdl-30487138

ABSTRACT

Genome-wide association studies have identified 40 ovarian cancer risk loci. However, the mechanisms underlying these associations remain elusive. In this study, we conducted a two-pronged approach to identify candidate causal SNPs and assess underlying biological mechanisms at chromosome 9p22.2, the first and most statistically significant associated locus for ovarian cancer susceptibility. Three transcriptional regulatory elements with allele-specific effects and a scaffold/matrix attachment region were characterized and, through physical DNA interactions, BNC2 was established as the most likely target gene. We determined the consensus binding sequence for BNC2 in vitro, verified its enrichment in BNC2 ChIP-seq regions, and validated a set of its downstream target genes. Fine-mapping by dense regional genotyping in over 15,000 ovarian cancer cases and 30,000 controls identified SNPs in the scaffold/matrix attachment region as among the most likely causal variants. This study reveals a comprehensive regulatory landscape at 9p22.2 and proposes a likely mechanism of susceptibility to ovarian cancer. SIGNIFICANCE: Mapping the 9p22.2 ovarian cancer risk locus identifies BNC2 as an ovarian cancer risk gene.See related commentary by Choi and Brown, p. 439.


Subject(s)
Carcinoma, Ovarian Epithelial/genetics , Chromosomes, Human, Pair 9 , Ovarian Neoplasms/genetics , Base Sequence , Cell Cycle Proteins/genetics , Cell Line, Tumor , Chromosome Mapping , Cystadenocarcinoma, Serous/genetics , DNA, Neoplasm/genetics , DNA-Binding Proteins/genetics , Female , Genetic Predisposition to Disease , Genome-Wide Association Study , HEK293 Cells , Humans , Linkage Disequilibrium , Polymorphism, Single Nucleotide
5.
Oncotarget ; 8(29): 46891-46899, 2017 Jul 18.
Article in English | MEDLINE | ID: mdl-28423358

ABSTRACT

Gene fusions play a critical role in some cancers and can serve as important clinical targets. In epithelial ovarian cancer (EOC), the contribution of fusions, especially by histological type, is unclear. We therefore screened for recurrent fusions in a histologically diverse panel of 220 EOCs using RNA sequencing. The Pipeline for RNA-Sequencing Data Analysis (PRADA) was used to identify fusions and allow for comparison with The Cancer Genome Atlas (TCGA) tumors. Associations between fusions and clinical prognosis were evaluated using Cox proportional hazards regression models. Nine recurrent fusions, defined as occurring in two or more tumors, were observed. CRHR1-KANSL1 was the most frequently identified fusion, identified in 6 tumors (2.7% of all tumors). This fusion was not associated with survival; other recurrent fusions were too rare to warrant survival analyses. One recurrent in-frame fusion, UBAP1-TGM7, was unique to clear cell (CC) EOC tumors (in 10%, or 2 of 20 CC tumors). We found some evidence that CC tumors harbor more fusions on average than any other EOC histological type, including high-grade serous (HGS) tumors. CC tumors harbored a mean of 7.4 fusions (standard deviation [sd] = 7.4, N = 20), compared to HGS EOC tumors mean of 2.0 fusions (sd = 3.3, N = 141). Few fusion genes were detected in endometrioid tumors (mean = 0.24, sd = 0.74, N = 55) or mucinous tumors (mean = 0.25, sd = 0.5, N = 4) tumors. To conclude, we identify one fusion at 10% frequency in the CC EOC subtype, but find little evidence for common (> 5% frequency) recurrent fusion genes in EOC overall, or in HGS subtype-specific EOC tumors.


Subject(s)
Gene Rearrangement , Genetic Association Studies , Neoplasms, Glandular and Epithelial/genetics , Neoplasms, Glandular and Epithelial/pathology , Oncogene Proteins, Fusion/genetics , Ovarian Neoplasms/genetics , Ovarian Neoplasms/pathology , Phenotype , Biomarkers, Tumor , Carcinoma, Ovarian Epithelial , Female , Gene Expression Regulation, Neoplastic , Humans , Neoplasm Grading , Prognosis , Translocation, Genetic
6.
Nat Genet ; 49(5): 680-691, 2017 May.
Article in English | MEDLINE | ID: mdl-28346442

ABSTRACT

To identify common alleles associated with different histotypes of epithelial ovarian cancer (EOC), we pooled data from multiple genome-wide genotyping projects totaling 25,509 EOC cases and 40,941 controls. We identified nine new susceptibility loci for different EOC histotypes: six for serous EOC histotypes (3q28, 4q32.3, 8q21.11, 10q24.33, 18q11.2 and 22q12.1), two for mucinous EOC (3q22.3 and 9q31.1) and one for endometrioid EOC (5q12.3). We then performed meta-analysis on the results for high-grade serous ovarian cancer with the results from analysis of 31,448 BRCA1 and BRCA2 mutation carriers, including 3,887 mutation carriers with EOC. This identified three additional susceptibility loci at 2q13, 8q24.1 and 12q24.31. Integrated analyses of genes and regulatory biofeatures at each locus predicted candidate susceptibility genes, including OBFC1, a new candidate susceptibility gene for low-grade and borderline serous EOC.


Subject(s)
Genetic Loci/genetics , Genetic Predisposition to Disease/genetics , Neoplasms, Glandular and Epithelial/genetics , Ovarian Neoplasms/genetics , Alleles , BRCA1 Protein/genetics , BRCA2 Protein/genetics , Carcinoma, Ovarian Epithelial , Female , Genome-Wide Association Study , Genotype , Humans , Meta-Analysis as Topic , Mutation , Neoplasms, Glandular and Epithelial/pathology , Ovarian Neoplasms/pathology , Polymorphism, Single Nucleotide , Risk Factors , Telomere-Binding Proteins/genetics
7.
Cancer Epidemiol Biomarkers Prev ; 25(3): 446-54, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26747452

ABSTRACT

BACKGROUND: While numerous susceptibility loci for epithelial ovarian cancer (EOC) have been identified, few associations have been reported with overall survival. In the absence of common prognostic genetic markers, we hypothesize that rare coding variants may be associated with overall EOC survival and assessed their contribution in two exome-based genotyping projects of the Ovarian Cancer Association Consortium (OCAC). METHODS: The primary patient set (Set 1) included 14 independent EOC studies (4,293 patients) and 227,892 variants, and a secondary patient set (Set 2) included six additional EOC studies (1,744 patients) and 114,620 variants. Because power to detect rare variants individually is reduced, gene-level tests were conducted. Sets were analyzed separately at individual variants and by gene, and then combined with meta-analyses (73,203 variants and 13,163 genes overlapped). RESULTS: No individual variant reached genome-wide statistical significance. A SNP previously implicated to be associated with EOC risk and, to a lesser extent, survival, rs8170, showed the strongest evidence of association with survival and similar effect size estimates across sets (Pmeta = 1.1E-6, HRSet1 = 1.17, HRSet2 = 1.14). Rare variants in ATG2B, an autophagy gene important for apoptosis, were significantly associated with survival after multiple testing correction (Pmeta = 1.1E-6; Pcorrected = 0.01). CONCLUSIONS: Common variant rs8170 and rare variants in ATG2B may be associated with EOC overall survival, although further study is needed. IMPACT: This study represents the first exome-wide association study of EOC survival to include rare variant analyses, and suggests that complementary single variant and gene-level analyses in large studies are needed to identify rare variants that warrant follow-up study. Cancer Epidemiol Biomarkers Prev; 25(3); 446-54. ©2016 AACR.


Subject(s)
Ovarian Neoplasms/genetics , Exome , Female , Genotype , Humans , Middle Aged , Ovarian Neoplasms/mortality , Survival Rate
8.
Genomics ; 106(6): 311-21, 2015 Dec.
Article in English | MEDLINE | ID: mdl-26363302

ABSTRACT

Survival after a diagnosis of ovarian cancer has not improved, and despite histological differences, treatment is similar for all cases. Understanding the molecular basis for ovarian cancer risk and prognosis is fundamental, and to this end much has been gleaned about genetic changes contributing to risk, and to a lesser extent, survival. There's considerable evidence for genetic differences between the four pathologically defined histological subtypes; however, the contribution of epigenetics is less well documented. In this report, we review alterations in DNA methylation in ovarian cancer, focusing on histological subtypes, and studies examining the roles of methylation in determining therapy response. As epigenetics is making its way into clinical care, we review the application of cell free DNA methylation to ovarian cancer diagnosis and care. Finally, we comment on recurrent limitations in the DNA methylation literature for ovarian cancer, which can and should be addressed to mature this field.


Subject(s)
DNA Methylation , Neoplasms, Glandular and Epithelial/genetics , Ovarian Neoplasms/genetics , Promoter Regions, Genetic/genetics , Adenocarcinoma, Mucinous/diagnosis , Adenocarcinoma, Mucinous/genetics , Carcinoma, Ovarian Epithelial , Cell Line, Tumor , Cystadenocarcinoma, Serous/diagnosis , Cystadenocarcinoma, Serous/genetics , Gene Expression Regulation, Neoplastic , Genome-Wide Association Study/methods , Humans , Neoplasms, Glandular and Epithelial/diagnosis , Ovarian Neoplasms/diagnosis
9.
Hum Genet ; 133(5): 481-97, 2014 May.
Article in English | MEDLINE | ID: mdl-24190013

ABSTRACT

Epithelial ovarian cancer (EOC) is a heterogeneous cancer with both genetic and environmental risk factors. Variants influencing the risk of developing the less-common EOC subtypes have not been fully investigated. We performed a genome-wide association study (GWAS) of EOC according to subtype by pooling genomic DNA from 545 cases and 398 controls of European descent, and testing for allelic associations. We evaluated for replication 188 variants from the GWAS [56 variants for mucinous, 55 for endometrioid and clear cell, 53 for low-malignant potential (LMP) serous, and 24 for invasive serous EOC], selected using pre-defined criteria. Genotypes from 13,188 cases and 23,164 controls of European descent were used to perform unconditional logistic regression under the log-additive genetic model; odds ratios (OR) and 95 % confidence intervals are reported. Nine variants tagging six loci were associated with subtype-specific EOC risk at P < 0.05, and had an OR that agreed in direction of effect with the GWAS results. Several of these variants are in or near genes with a biological rationale for conferring EOC risk, including ZFP36L1 and RAD51B for mucinous EOC (rs17106154, OR = 1.17, P = 0.029, n = 1,483 cases), GRB10 for endometrioid and clear cell EOC (rs2190503, P = 0.014, n = 2,903 cases), and C22orf26/BPIL2 for LMP serous EOC (rs9609538, OR = 0.86, P = 0.0043, n = 892 cases). In analyses that included the 75 GWAS samples, the association between rs9609538 (OR = 0.84, P = 0.0007) and LMP serous EOC risk remained statistically significant at P < 0.0012 adjusted for multiple testing. Replication in additional samples will be important to verify these results for the less-common EOC subtypes.


Subject(s)
Alleles , DNA/genetics , Genetic Predisposition to Disease , Genome-Wide Association Study , Neoplasms, Glandular and Epithelial/genetics , Ovarian Neoplasms/genetics , Carcinoma, Ovarian Epithelial , Female , Humans , Polymorphism, Single Nucleotide , Quality Control
10.
BMC Res Notes ; 6: 425, 2013 Oct 22.
Article in English | MEDLINE | ID: mdl-24148579

ABSTRACT

BACKGROUND: Mitochondria are the site of oxidative phosphorylation, a process which generates reactive oxygen species (ROS). Elevated ROS levels can lead to oxidative stress, a cellular state implicated in carcinogenesis. It is hypothesized that alternations in mitochondrial (MT) DNA, including heritable MT single nucleotide polymorphisms (MT-SNPs), have the potential to change the capacity of MT function, leading to increased oxidative stress and cancer risk. We investigated if common MT-SNPs and/or haplogroups and are associated with invasive serous ovarian cancer (OvCa) risk. METHODS: A panel of 64 MT-SNPs designed to tag all common variation in the European MT genome (minor allele frequency (MAF) >1%, r^2 >0.8) was genotyped in study participants of European descent using the Sequenom MassARRAY iPlex Gold® system (Sequenom Inc, CA, USA). Invasive serous OvCa cases (n = 405) and frequency age-matched controls (n = 445) were drawn from a population-based case-control study of OvCa in western Canada. Binary logistic regression was used to estimate the odds ratio (OR) and 95% confidence intervals (C.I.) for carriage of the minor versus major allele by case-control status. MitoTool was used to test the relationship between European haplogroup status and case-control status using Fisher's exact test. RESULTS: The most significant disease-SNP association was for rs2857285, a synonymous MT-SNP in ND4 (OR = 4.84, 95% CI: 1.03-22.68, P = 0.045). After adjustment for multiple testing using a Bonferroni correction of the Type 1 error this MT-SNP was not significant. No other MT-SNP had a P-value < 0.05. European haplogroup status was not associated with case status. Most MT-SNPs (73%) genotyped had a MAF <5%. CONCLUSION: Common European MT-SNPs (MAF > 5%) and haplogroups were not associated with invasive serous OvCa risk in this study; however, most European MT-SNPs have a low MAF (<5%), which we were underpowered to adequately assess. Larger studies are needed to clarify the role of low MAF MT-SNPs (MAF < 5%) in invasive serous OvCa risk.


Subject(s)
DNA, Mitochondrial/genetics , Inheritance Patterns , Mitochondria/genetics , Neoplasms, Glandular and Epithelial/genetics , Ovarian Neoplasms/genetics , Polymorphism, Single Nucleotide , Aged , Alleles , Canada , Carcinoma, Ovarian Epithelial , Case-Control Studies , Female , Gene Frequency , Haplotypes , Humans , Logistic Models , Middle Aged , Mitochondria/pathology , NADH Dehydrogenase/genetics , Neoplasms, Glandular and Epithelial/ethnology , Neoplasms, Glandular and Epithelial/pathology , Odds Ratio , Ovarian Neoplasms/ethnology , Ovarian Neoplasms/pathology , Ovary/metabolism , Ovary/pathology , Oxidative Stress , Reactive Oxygen Species/metabolism , Risk , White People
11.
Hum Reprod ; 28(7): 1987-94, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23592221

ABSTRACT

STUDY QUESTION: Do differences in heritable genetic factors explain some of the difference in age at natural menopause (ANM) among populations? SUMMARY ANSWER: One single nucleotide polymorphism (SNP)-ANM association (rs16991615) detected in European women was replicated in Iranian women. WHAT IS KNOWN ALREADY: Genetics plays an important role in ANM, and well-powered genome-wide association studies (GWAS) of ANM performed in European women have discovered many statistically significant SNP-ANM associations. Average ANM varies by ethnicity, and population-specific differences in ANM-associated alleles may in part explain these differences. STUDY DESIGN, SIZE, DURATION: After quality control procedures, 97 SNPs were analyzed in genotype data of 828 Iranian women who experienced natural menopause. SNP genotyping data were used to perform linear regression analyses with ANM as a quantitative trait. Study participants were drawn from the population-based Tehran Lipid and Glucose Study based in Tehran, Iran. This study was performed between February 2009 and March 2012. PARTICIPANTS/MATERIALS, SETTING AND METHODS: Based on an ANM-GWAS literature review, eight SNPs at four loci previously associated with ANM in European women were tested for replication in Iranian women. Linear regression analyses were performed including (n = 828) and excluding (n = 783) women who experience premature ovarian failure (ANM before 40 years of age). In addition, to search for novel population-specific ANM risk alleles, a pool-based GWAS was performed using this collection of Iranian women. Two DNA pools were constructed and compared: an 'early' ANM pool (lower 20(th) percentile of menopause ages, 40-45 years, n = 165) and a 'late' ANM pool (upper 20(th) percentile of menopause ages, 54-65 years, n = 187). Each DNA pool was assayed on four Illumina Human1M-Duo arrays, and allele-based tests of association were used to rank SNPs. One hundred and two highly ranked SNPs were chosen for individual genotyping by Sequenom MassARRAY and association analysis in the Iranian women. MAIN RESULTS AND THE ROLE OF CHANCE: One SNP-ANM association previously detected in European women was replicated in Iranian women (rs16991615; ß = 1.07, standard error (SE): 0.49, P = 0.02). SNPs at the previously reported 19q13.42 and 6p24.2 loci also approached statistical significance and had consistent SNP effects (magnitude and direction) in Iranian women (rs1172822; ß = -0.39, SE: 0.22, P = 0.08; and rs2153157, ß = 0.41, SE: 0.21, P = 0.05). We found little evidence for novel SNP-ANM associations in Iranian women; no SNP selected based on the pool-based GWAS achieved genome-wide significance. LIMITATIONS, REASONS FOR CAUTION: Due to small sample size this study was powered to reliably detect only moderate-to-large SNP effect sizes. This limited our ability to replicate many of the previously reported SNP-ANM risk alleles and to discover novel SNP-ANM associations' specific to the Iranian population. In performing our pool-based GWAS, a reduction in power was introduced relative to a conventional GWAS. WIDER IMPLICATIONS OF THE FINDINGS: Our results imply that European and Iranian women share ANM-associated genetic variants. Our study was underpowered but for all SNPs tested the direction of the effect was consistent with data from the European study. Therefore, we anticipate that many (if not all) of the ANM-associated SNPs discovered in European women will replicate in Iranian women upon genotyping a sufficient number of women. Our data do not support the hypothesis that population-specific SNP-ANM associations explain population-specific differences in the mean ANM.


Subject(s)
Menopause/genetics , Age Factors , Aged , Europe/epidemiology , Female , Genetic Association Studies , Genotype , Humans , Iran/epidemiology , Linear Models , Middle Aged , Polymorphism, Single Nucleotide
12.
BMC Med Genomics ; 4: 81, 2011 Nov 28.
Article in English | MEDLINE | ID: mdl-22122996

ABSTRACT

BACKGROUND: Until recently, genome-wide association studies (GWAS) have been restricted to research groups with the budget necessary to genotype hundreds, if not thousands, of samples. Replacing individual genotyping with genotyping of DNA pools in Phase I of a GWAS has proven successful, and dramatically altered the financial feasibility of this approach. When conducting a pool-based GWAS, how well SNP allele frequency is estimated from a DNA pool will influence a study's power to detect associations. Here we address how to control the variance in allele frequency estimation when DNAs are pooled, and how to plan and conduct the most efficient well-powered pool-based GWAS. METHODS: By examining the variation in allele frequency estimation on SNP arrays between and within DNA pools we determine how array variance [var(e(array))] and pool-construction variance [var(e(construction))] contribute to the total variance of allele frequency estimation. This information is useful in deciding whether replicate arrays or replicate pools are most useful in reducing variance. Our analysis is based on 27 DNA pools ranging in size from 74 to 446 individual samples, genotyped on a collective total of 128 Illumina beadarrays: 24 1M-Single, 32 1M-Duo, and 72 660-Quad. RESULTS: For all three Illumina SNP array types our estimates of var(e(array)) were similar, between 3-4 × 10-4 for normalized data. Var(e(construction)) accounted for between 20-40% of pooling variance across 27 pools in normalized data. CONCLUSIONS: We conclude that relative to var(e(array)), var(e(construction)) is of less importance in reducing the variance in allele frequency estimation from DNA pools; however, our data suggests that on average it may be more important than previously thought. We have prepared a simple online tool, PoolingPlanner (available at http://www.kchew.ca/PoolingPlanner/), which calculates the effective sample size (ESS) of a DNA pool given a range of replicate array values. ESS can be used in a power calculator to perform pool-adjusted calculations. This allows one to quickly calculate the loss of power associated with a pooling experiment to make an informed decision on whether a pool-based GWAS is worth pursuing.


Subject(s)
DNA/genetics , Genome-Wide Association Study/methods , Analysis of Variance , Computational Biology , Gene Frequency , Humans , Polymorphism, Single Nucleotide/genetics , Sample Size
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