Genome-Wide Association Study of Serum Creatinine Levels during Vancomycin Therapy

Vancomycin, a commonly used antibiotic, can be nephrotoxic. Known risk factors such as age, creatinine clearance, vancomycin dose / dosing interval, and concurrent nephrotoxic medications fail to accurately predict nephrotoxicity. To identify potential genomic risk factors, we performed a genome-wide association study (GWAS) of serum creatinine levels while on vancomycin in 489 European American individuals and validated findings in three independent cohorts totaling 439 European American individuals. In primary analyses, the chromosome 6q22.31 locus was associated with increased serum creatinine levels while on vancomycin therapy (most significant variant rs2789047, risk allele A, β = -0.06, p = 1.1 x 10^-7). SNPs in this region had consistent directions of effect in the validation cohorts, with a meta-p of 1.1 x 10^-7. Variation in this region on chromosome 6, which includes the genes TBC1D32/C6orf170 and GJA1 (encoding connexin43), may modulate risk of vancomycin-induced kidney injury.

Disclosing genetic risk for coronary heart disease: effects on perceived personal control and genetic counseling satisfaction

We investigated whether disclosure of coronary heart disease (CHD) genetic risk influences perceived personal control (PPC) and genetic counseling satisfaction (GCS). Participants (n = 207, age: 45-65 years) were randomized to receive estimated 10-year risk of CHD based on a conventional risk score (CRS) with or without a genetic risk score (GRS). Risk estimates were disclosed by a genetic counselor who also reviewed how GRS altered risk in those randomized to CRS+GRS. Each participant subsequently met with a physician and then completed surveys to assess PPC and GCS. Participants who received CRS+GRS had higher PPC than those who received CRS alone although the absolute difference was small (25.2 ± 2.7 vs 24.1 ± 3.8, p = 0.04). A greater proportion of CRS+GRS participants had higher GCS scores (17.3 ± 5.3 vs 15.9 ± 6.3, p = 0.06). In the CRS+GRS group, PPC and GCS scores were not correlated with GRS. Within both groups, PPC and GCS scores were similar in patients with or without family history (p = NS). In conclusion, patients who received their genetic risk of CHD had higher PPC and tended to have higher GCS. Our findings suggest that disclosure of genetic risk of CHD together with conventional risk estimates is appreciated by patients. Whether this results in improved outcomes needs additional investigation.

Ventricular septal defect and bivalvular endocarditis

A 63-year-old man presented with generalized fatigue, chills, malaise, dyspnea, intermittent fevers, and 50-pound weight loss of 4 months' duration. Blood cultures were positive for pan-sensitive Streptococcus anginosus. Transesophageal echocardiography showed an 11 mm × 3 mm mobile mass attached to the mitral valve, a 16 mm × 16 mm mobile mass attached to the pulmonary valve, and a small membranous ventricular septal defect. The patient received 12 weeks of intravenous (IV) antibiotics with eventual resolution of the masses. Multi-valve endocarditis involving both the left and right chambers is rarely reported without prior history of IV drug use or infective endocarditis. Our case emphasizes the importance of careful assessment for ventricular septal defects or extra-cardiac shunts in individuals who present with simultaneous right and left-sided endocarditis.

Abstract 212: Temporal Trends of SPECT Myocardial Perfusion Imaging in Patients with Coronary Heart Disease: A 22-Year Experience from a Tertiary Academic Medical Center

Background: Over the past 20 years, there has been an increasing decline in the prevalence of abnormal stress single-photon emission computed tomography myocardial perfusion imaging (SPECT) studies among patients with no history of coronary artery disease (CAD). The trend of SPECT studies among patients with known CAD has not been evaluated before.

Methods: Using the Mayo Clinic nuclear cardiology database, we examined all stress SPECT tests performed between 1/1991-12/2012 in patients with prior history of CAD defined as having prior myocardial infarction, percutaneous coronary intervention, and/or coronary artery bypass grafting. Patients with left bundle branch block, paced rhythm, bicycle or rest-only tests, cardiomyopathy, valvular heart disease, and technically unsatisfactory studies were excluded. The study cohort was divided into 5 time periods: 1991-5, 1996-2000, 2001-5, 2006-10, and 2011-12.

Results: There were 19373 eligible SPECT tests (mean age 66.2 ± 10.9y, 75.4% men). Annual utilization of SPECT studies in patients with history of CAD increased from an average of 495 tests per year between 1991-1995 to a peak of 1425 in 2003; and then decreased to 552 tests in 2012. Asymptomatic patients comprised 33% in 1991-1995, peaked at 48% in 2006, and then decreased back to 31% in 2012. Over time, patients with typical angina decreased while patients with dyspnea increased, P <0.001 (Fig 1). The percentage of high risk SPECT tests significantly decreased, and the percentage of low-risk SPECT tests significantly increased despite the overall decline of SPECT utilization between 2003 and 2012. Almost 80% of all tests performed in 2012 had a low risk summed stress score compared to 29% in 1991, P <0.001 (Fig 2).

Conclusions: In Mayo Clinic Rochester, annual SPECT utilization in patients with prior CAD increased between 1992 and 2003, but then decreased significantly after 2003. Fewer patients had typical angina while patients with dyspnea increased over time. High risk SPECT tests declined while low risk tests increased dramatically. These data suggest that stress SPECT was being increasingly utilized in CAD patients without typical angina who are at low risk.

The ATXN2-SH2B3 locus is associated with peripheral arterial disease: an electronic medical record-based genome-wide association study

OBJECTIVES

In contrast to coronary heart disease (CHD), genetic variants that influence susceptibility to peripheral arterial disease (PAD) remain largely unknown.

BACKGROUND

We performed a two-stage genomic association study leveraging an electronic medical record (EMR) linked-biorepository to identify genetic variants that mediate susceptibility to PAD.

METHODS

PAD was defined as a resting/post-exercise ankle-brachial index (ABI) ≤0.9 or ≥1.4 and/or history of lower extremity revascularization. Controls were patients without history of PAD. In Stage I we performed a genome-wide association analysis adjusting for age and sex, of 537, 872 SNPs in 1641 PAD cases (66 ± 11 years, 64% men) and 1604 control subjects (61 ± 7 year, 60% men) of European ancestry. In Stage II we genotyped the top 48 SNPs that were associated with PAD in Stage I, in a replication cohort of 740 PAD cases (70 ± 11 year, 63% men) and 1051 controls (70 ± 12 year, 61% men).

RESULTS

The SNP rs653178 in the ATXN2-SH2B3 locus was significantly associated with PAD in the discovery cohort (OR = 1.23; P = 5.59 × 10(-5)), in the replication cohort (OR = 1.22; 8.9 × 10(-4)) and in the combined cohort (OR = 1.22; P = 6.46 × 10(-7)). In the combined cohort this SNP remained associated with PAD after additional adjustment for cardiovascular risk factors including smoking (OR = 1.22; P = 2.15 × 10(-6)) and after excluding patients with ABI > 1.4 (OR = 1.24; P = 3.98 × 10(-7)). The SNP is in near-complete linkage disequilibrium (LD) (r (2) = 0.99) with a missense SNP (rs3184504) in SH2B3, a gene encoding an adapter protein that plays a key role in immune and inflammatory response pathways and vascular homeostasis. The SNP has pleiotropic effects and has been previously associated with multiple phenotypes including myocardial infarction.

CONCLUSIONS

Our findings suggest that the ATXN2-SH2B3 locus influences susceptibility to PAD.

A genome- and phenome-wide association study to identify genetic variants influencing platelet count and volume and their pleiotropic effects

Platelets are enucleated cell fragments derived from megakaryocytes that play key roles in hemostasis and in the pathogenesis of atherothrombosis and cancer. Platelet traits are highly heritable and identification of genetic variants associated with platelet traits and assessing their pleiotropic effects may help to understand the role of underlying biological pathways. We conducted an electronic medical record (EMR)-based study to identify common variants that influence inter-individual variation in the number of circulating platelets (PLT) and mean platelet volume (MPV), by performing a genome-wide association study (GWAS). We characterized genetic variants associated with MPV and PLT using functional, pathway and disease enrichment analyses; we assessed pleiotropic effects of such variants by performing a phenome-wide association study (PheWAS) with a wide range of EMR-derived phenotypes. A total of 13,582 participants in the electronic MEdical Records and GEnomic network had data for PLT and 6,291 participants had data for MPV. We identified five chromosomal regions associated with PLT and eight associated with MPV at genome-wide significance (P < 5E-8). In addition, we replicated 20 SNPs [out of 56 SNPs (α: 0.05/56 = 9E-4)] influencing PLT and 22 SNPs [out of 29 SNPs (α: 0.05/29 = 2E-3)] influencing MPV in a published meta-analysis of GWAS of PLT and MPV. While our GWAS did not find any new associations, our functional analyses revealed that genes in these regions influence thrombopoiesis and encode kinases, membrane proteins, proteins involved in cellular trafficking, transcription factors, proteasome complex subunits, proteins of signal transduction pathways, proteins involved in megakaryocyte development, and platelet production and hemostasis. PheWAS using a single-SNP Bonferroni correction for 1,368 diagnoses (0.05/1368 = 3.6E-5) revealed that several variants in these genes have pleiotropic associations with myocardial infarction, autoimmune, and hematologic disorders. We conclude that multiple genetic loci influence interindividual variation in platelet traits and also have significant pleiotropic effects; the related genes are in multiple functional pathways including those relevant to thrombopoiesis.

Downstream clinical implications of abnormal myocardial perfusion single-photon emission computed tomography based on appropriate use criteria

BACKGROUND

Appropriate use criteria (AUC) for single-photon emission computed tomography myocardial perfusion images (SPECT-MPI) were developed to address the growth of cardiac imaging studies. However, these criteria have not been vigorously validated. We sought to determine the rate of abnormal stress SPECT-MPI studies and subsequent revascularization procedures as categorized by AUC.

METHODS

We retrospectively examined 280 patients who underwent stress SPECT-MPI and categorized these studies as appropriate, inappropriate, or uncertain based on AUC. Data regarding subsequent angiography and revascularization within 6 months after stress SPECT-MPI were collected from the electronic medical record.

RESULTS

280 patients met the inclusion criteria (mean age 67.3 ± 11.4 years, 36 % female). When categorized by AUC, 62.9 % (N = 176) of stress SPECT-MPI were considered appropriate, 13.6 % (N = 38) uncertain, and 23.6 % (N = 66) inappropriate. Appropriate stress SPECT-MPI studies were more likely to have intermediate or high risk results than uncertain or inappropriate studies [40 % (N = 71) vs. 21 % (N = 8) and 18 % (N = 12), respectively; P = 0.008)]. Appropriate studies were associated with an increased rate of coronary angiography [14 % (N = 25)] compared to the uncertain (0 %) and inappropriate [3 % (N = 2)] studies (P = 0.003). There was also an increased rate of revascularization after appropriate studies [9 % (N = 16)] compared to the uncertain (0 %) and inappropriate (0 %) studies (P = 0.006).

CONCLUSIONS

Appropriate stress SPECT-MPI studies are more likely to result in abnormal results requiring subsequent revascularization compared to inappropriate and uncertain stress studies. Inappropriate and uncertain stress SPECT-MPI did not lead to subsequent revascularization.

Clinical Correlates of Autosomal Chromosomal Abnormalities in an Electronic Medical Record-Linked Genome-Wide Association Study: A Case Series

Although mosaic autosomal chromosomal abnormalities are being increasingly detected as part of high-density genotyping studies, the clinical correlates are unclear. From an electronic medical record (EMR)–based genome-wide association study (GWAS) of peripheral arterial disease, log-R-ratio and B-allele-frequency data were used to identify mosaic autosomal chromosomal abnormalities including copy number variation and loss of heterozygosity. The EMRs of patients with chromosomal abnormalities and those without chromosomal abnormalities were reviewed to compare clinical characteristics. Among 3336 study participants, 0.75% (n = 25, mean age = 74.8 ± 10.7 years, 64% men) had abnormal intensity plots indicative of autosomal chromosomal abnormalities. A hematologic malignancy was present in 8 patients (32%), of whom 4 also had a solid organ malignancy while 2 patients had a solid organ malignancy only. In 50 age- and sex-matched participants without chromosomal abnormalities, there was a lower rate of hematologic malignancies (2% vs 32%, P < .001) but not solid organ malignancies (20% vs 24%, P = .69). We also report the clinical characteristics of each patient with the observed chromosomal abnormalities. Interestingly, among 5 patients with 20q deletions, 4 had a myeloproliferative disorder while all 3 men in this group had prostate cancer. In summary, in a GWAS of 3336 adults, 0.75% had autosomal chromosomal abnormalities and nearly a third of them had hematologic malignancies. A potential novel association between 20q deletions, myeloproliferative disorders, and prostate cancer was also noted.

Clinical Correlates of Autosomal Chromosomal Abnormalities in an Electronic Medical Record-Linked Genome-Wide Association Study: A Case Series

Although mosaic autosomal chromosomal abnormalities are being increasingly detected as part of high-density genotyping studies, the clinical correlates are unclear. From an electronic medical record (EMR)-based genome-wide association study (GWAS) of peripheral arterial disease, log-R-ratio and B-allele-frequency data were used to identify mosaic autosomal chromosomal abnormalities including copy number variation and loss of heterozygosity. The EMRs of patients with chromosomal abnormalities and those without chromosomal abnormalities were reviewed to compare clinical characteristics. Among 3336 study participants, 0.75% (n = 25, mean age = 74.8 ± 10.7 years, 64% men) had abnormal intensity plots indicative of autosomal chromosomal abnormalities. A hematologic malignancy was present in 8 patients (32%), of whom 4 also had a solid organ malignancy while 2 patients had a solid organ malignancy only. In 50 age- and sex-matched participants without chromosomal abnormalities, there was a lower rate of hematologic malignancies (2% vs 32%, P < .001) but not solid organ malignancies (20% vs 24%, P = .69). We also report the clinical characteristics of each patient with the observed chromosomal abnormalities. Interestingly, among 5 patients with 20q deletions, 4 had a myeloproliferative disorder while all 3 men in this group had prostate cancer. In summary, in a GWAS of 3336 adults, 0.75% had autosomal chromosomal abnormalities and nearly a third of them had hematologic malignancies. A potential novel association between 20q deletions, myeloproliferative disorders, and prostate cancer was also noted.

Abstract 40: Temporal Trends of SPECT Myocardial Perfusion Imaging in Patients without Coronary Artery Disease: A 17-Year Experience from a Tertiary Academic Medical Center

Background: Between 1990-2006, there was a tremendous increase in utilization of single photon emission computed tomography myocardial perfusion imaging (SPECT). Characteristics of the observed increase of SPECT utilization have never been studied.

Methods: Using the Mayo Clinic nuclear cardiology database, we examined all SPECT tests performed between 1/1/1991-12/31/2007 in patients without prior coronary artery disease (CAD). Patients with history of CAD, left bundle branch block, paced rhythm, bicycle/ rest-only tests, cardiomyopathy, valvular heart disease, and technically unsatisfactory studies were excluded. The study cohort was divided into 4 time periods: 1991-5, 1996-2000, 2001-5, and 2006-7.

Results: There were 29255 eligible SPECT tests (mean age 62.4 ± 12y, 54% men). Annual utilization of SPECT studies increased from 682 in 1992 to a peak of 2738 in 2002, and then decreased to 2134 in 2007, Fig 1. There were very modest changes in CAD risk factors over time. Testing of asymptomatic patients nearly doubled (21.9% in 1991-5 to 42.7% in 2006-7). Tests on patients with typical angina decreased dramatically (18.3% in 1991-5 to 5.3% in 2006-7), Fig 2. Summed stress score, summed difference score, and high risk SPECT tests decreased over time, Fig 3. Normal SPECT studies and negative study ECG increased for both pharmacologic and exercise tests.

Conclusions: In Mayo Clinic Rochester, annual SPECT utilization in patients without prior CAD increased between 1992 and 2002, but then decreased in advance of national trends. Normal tests increased, while summed stress score, summed difference score, and high risk tests all decreased. These data suggest that SPECT was increasingly utilized in patients with a lower prevalence of CAD.

Hypercalcemia, Renal Failure, and Skull Lytic Lesions: Follicular Lymphoma Masquerading as Multiple Myeloma

The findings of hypercalcemia, skull lytic lesions, and renal failure are usually characteristic for multiple myeloma. We herein describe an interesting case of B-cell follicular lymphoma that presented with many features mimicking multiple myeloma.

Genetic Loci implicated in erythroid differentiation and cell cycle regulation are associated with red blood cell traits

OBJECTIVE

To identify common genetic variants influencing red blood cell (RBC) traits.

PATIENTS AND METHODS

We performed a genomewide association study from June 2008 through July 2011 of hemoglobin, hematocrit, RBC count, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration in 12,486 patients of European ancestry from the electronic MEdical Records and Genomics (eMERGE) network. We developed an electronic medical record-based algorithm that included individuals who had RBC measurements obtained for clinical care and excluded values measured in the setting of hematopoietic disorders, comorbid conditions, or medications known to affect RBC production or a recent history of blood loss.

RESULTS

We identified 4 new genetic loci and replicated 11 loci previously reported to be associated with one or more RBC traits in individuals of European ancestry. Notably, genes present in 3 of the 4 newly identified loci (THRB, PTPLAD1, CDT1) and in 6 of the 11 replicated loci (KLF1, ALDH8A1, CCND3, SPTA1, FBXO7, TFR2/EPO) are implicated in erythroid differentiation and regulation of cell cycle in hematopoietic stem cells.

CONCLUSION

Genes in the erythroid differentiation and cell cycle regulation pathways influence interindividual variation in RBC indices. Our results provide insights into the molecular basis underlying variation in RBC traits.

Serum N-terminal pro-B-type natriuretic peptide levels are associated with functional capacity in patients with peripheral arterial disease

We hypothesized that higher serum levels of N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) are associated with lower functional capacity in patients with peripheral arterial disease ([PAD] n = 481, mean age 67, 68% men). Functional capacity was quantified as distance walked on a treadmill for 5 minutes. Patients were divided into 3 groups according to the distance walked: >144 yards (group 1, n = 254); 60 to 144 yards (group 2, n = 80); <60 yards or did not walk (group 3, n = 147). The association between NT-pro-BNP levels and the ordinal 3-level walking distance was assessed using multivariable ordinal logistic regression analyses that adjusted for several possible confounding variables. Higher levels of NT-pro-BNP were associated with a lower ordinal walking category independent of possible confounders (odds ratio [OR] 1.51, 95% confidence interval [CI] 1.28-1.77; P < .001). In conclusion, higher levels of NT-pro-BNP are independently associated with lower functional capacity in patients with PAD and may be a marker of hemodynamic stress in these patients.