Search results for: Alexander M. Walker

Items from 1 to 20 out of 55 results

article

Stratified analysis in comparative effectiveness studies that emulate randomized trials

Phyo T. Htoo, Robert J. Glynn, Shirley Wang, Julie M. Paik, more

Pharmacoepidemiology and Drug Safety > 33 > 1 > n/a - n/a

Purpose For observational cohort studies that employ matching by propensity scores (PS), preliminary stratification by consequential predictors of outcome better emulates stratified randomization and potentially reduces variance and bias through relaxed dependence on modeling assumptions. We assessed the impact of pre‐stratification in two real‐life examples. For both, prior evidence from placebo‐controlled...

article

The acute effects of azithromycin use on cardiovascular mortality as compared with amoxicillin–clavulanate in US Veterans

Maral DerSarkissian, Yinong Young‐Xu, Mei Sheng Duh, Rachel H. Bhak, more

Pharmacoepidemiology and Drug Safety > 31 > 8 > 840 - 850

Purpose Azithromycin is a common first‐line antibiotic for respiratory infection; however, there is conflicting evidence regarding risk of cardiovascular death. We assessed cardiovascular and noncardiovascular mortality associated with azithromycin versus amoxicillin–clavulanate among US Veterans treated for nonear–nose–throat respiratory infection (“respiratory”) or ear–nose–throat infection indication...

article

Sequential surveillance for drug safety in a regulatory environment

David Martin, Joshua J. Gagne, Susan Gruber, Rima Izem, more

Pharmacoepidemiology and Drug Safety > 27 > 7 > 707 - 712

article

Reuse of data sources to evaluate drug safety signals: When is it appropriate?

Shirley V. Wang, Martin Kulldorff, Robert J. Glynn, Joshua J. Gagne, more

Pharmacoepidemiology and Drug Safety > 27 > 6 > 567 - 569

article

A Case Study of the Incremental Utility for Disease Identification of Natural Language Processing in Electronic Medical Records

Lisa S. Weiss, Xiaofeng Zhou, Alexander M. Walker, Ashwin N. Ananthakrishnan, more

Pharmaceutical Medicine > 2018 > 32 > 1 > 31-37

Background Information exists as unstructured medical text in healthcare databases. Such information is not routinely considered in safety surveillance but typically relies solely on structured (coded) data. Natural language processing (NLP) may allow the capture of concepts from unstructured data and thus enhance safety surveillance capability. Objectives We sought to assess the added contribution...

article

For drug-induced carcinogenesis, the observations are the hypothesis

Alexander M. Walker

Annals of Epidemiology > 2016 > 26 > 11 > 749-750

article

Computer-assisted expert case definition in electronic health records

Alexander M. Walker, Xiaofeng Zhou, Ashwin N. Ananthakrishnan, Lisa S. Weiss, more

International Journal of Medical Informatics > 2016 > 86 > Complete > 62-70

To describe how computer-assisted presentation of case data can lead experts to infer machine-implementable rules for case definition in electronic health records. As an illustration the technique has been applied to obtain a definition of acute liver dysfunction (ALD) in persons with inflammatory bowel disease (IBD).The technique consists of repeatedly sampling new batches of case candidates from...

article

Identifying health outcomes in healthcare databases

Stephan Lanes, Jeffrey S. Brown, Kevin Haynes, Michael F. Pollack, more

Pharmacoepidemiology and Drug Safety > 24 > 10 > 1009 - 1016

PurposeThe purpose of this review is to assist researchers in developing, using, and interpreting case‐identifying algorithms in electronic healthcare databases. MethodsWe review clinical characteristics of health outcomes, data settings and informatics, and epidemiologic and statistical methods aspects as they pertain to the development and use of case‐identifying algorithms. ResultsWe offer a...

article

Acute Nonarteritic Anterior Ischemic Optic Neuropathy and Exposure to Phosphodiesterase Type 5 Inhibitors

Ulka B. Campbell, Alexander M. Walker, Michael Gaffney, Kenneth R. Petronis, more

The Journal of Sexual Medicine > 12 > 1 > 139 - 151

IntroductionNonarteritic anterior ischemic optic neuropathy (NAION), a rare visual disorder, has been reported in men using phosphodiesterase type 5 inhibitors (PDE5i) for erectile dysfunction. AimWe examined whether intermittent use of PDE5i is associated with acute NAION onset within approximately five half‐lives following drug ingestion. MethodsOne hundred two ophthalmology centers in the United...

article

Characteristics of study design and elements that may contribute to the success of electronic safety monitoring systems

Carlos Bell, Aloka Chakravarty, Susan Gruber, Susan R. Heckbert, more

Pharmacoepidemiology and Drug Safety > 23 > 11 > 1223 - 1225

article

Cardiac mortality in users of olmesartan, other angiotensin‐receptor blockers and angiotensin‐converting enzyme inhibitors

Alexander M. Walker, Caihua Liang, C. Robin Clifford, Crawford Parker, more

Pharmacoepidemiology and Drug Safety > 23 > 4 > 348 - 356

PurposeClinical trials of olmesartan for prevention of progression of renal disease in patients with diabetes showed renal protection but an unexpected imbalance in cardiac deaths. The US Food and Drug Administration requested from the manufacturer a cohort study of olmesartan, other angiotensin‐receptor blockers (ARBs), and angiotensin‐converting enzyme (ACE) inhibitors in a large population. MethodsA...

article

Matching on provider is risky

Alexander M. Walker

Journal of Clinical Epidemiology > 2013 > 66 > 8 Supplement > S65-S68

To illustrate that matching on provider may exacerbate, not remove, bias.The degree of confounding bias depends in part on the proportions of treatment variation that can be ascribed to confounders and to instruments, respectively. This commentary raises the specific example of bias by matching on hospital induced in a study of coronary artery bypass graft surgery patients and illustrates the effect...

article

Risk of Guillain–Barré syndrome after meningococcal conjugate vaccination

Priscilla Velentgas, Anthony A. Amato, Rhonda L. Bohn, K. Arnold Chan, more

Pharmacoepidemiology and Drug Safety > 21 > 12 > 1350 - 1358

PurposeA new meningococcal conjugate vaccine (MCV4) was introduced in 2005. Shortly after, case reports of Guillain–Barré syndrome (GBS), a serious demyelinating disease, began to be reported to the Vaccine Adverse Event Reporting System. In 2006, the Centers for Disease Control and Prevention and the Food and Drug Administration requested the evaluation of GBS risk after MCV4 vaccination. We conducted...

article

Transarticular Facet Screw Stabilization and Dorsal Laminectomy in 26 Dogs with Degenerative Lumbosacral Stenosis with Instability

Elyshia J. Hankin, Richard M. Jerram, Alexander M. Walker, Michael D. King, more

Veterinary Surgery > 41 > 5 > 611 - 619

ObjectiveTo describe outcome after transarticular facet screw stabilization and dorsal laminectomy for treatment of dynamic degenerative lumbosacral stenosis (DLS) in 26 dogs. Study DesignRetrospective case series. AnimalsDogs (n = 26) with dynamic DLS. MethodsMedical records (2004–2009) of dogs treated with transarticular facet screw stabilization and dorsal laminectomy were reviewed. Dogs (n...

article

An Event‐Based Approach for Comparing the Performance of Methods for Prospective Medical Product Monitoring

Joshua J. Gagne, Alexander M. Walker, Robert J. Glynn, Jeremy A. Rassen, more

Pharmacoepidemiology and Drug Safety > 21 > 6 > 631 - 639

BackgroundProspective medical product monitoring is intended to alert stakeholders about whether and when safety problems are identifiable in longitudinal electronic healthcare data. Little attention has been given to how to compare methods in this setting. PurposeTo explore aspects of prospective monitoring that should be considered when comparing method performance and to develop a metric that explicitly...

article

Identification of esophageal cancer in the General Practice Research Database

Alexander M. Walker

Pharmacoepidemiology and Drug Safety > 20 > 11 > 1159 - 1167

BackgroundStudies based on the first appearance of a code for esophageal cancer in the General Practice Research Database (GPRD) have yielded conflicting results concerning the relationship between disease onset and prior bisphosphonate use. The literature on the timing of cancer code appearance in general practice records is scanty but suggests that there may be substantial error by comparison with...

article

Orthogonal predictions: follow‐up questions for suggestive data

Alexander M. Walker

Pharmacoepidemiology and Drug Safety > 19 > 5 > 529 - 532

When a biological hypothesis of causal effect can be inferred, the hypothesis can sometimes be tested in the selfsame database that gave rise to the study data from which the hypothesis grew. Valid testing happens when the inferred biological hypothesis has scientific implications that predict new relations between observations already recorded. Testing for the existence of the new relations is a...

article

Health care resource utilization in patients with active epilepsy

Tobias Kurth, Barbara E. Lewis, Alexander M. Walker

Epilepsia > 51 > 5 > 874 - 882

Purpose: To evaluate health care resource utilization (HRU) in active epilepsy. Methods: Thomson‐Reuters insurance databases included 14 million persons in 2005–2007. We extracted information for individuals with insurance claims suggestive of epilepsy. Using iterative expert classification, we sorted patients by type of epilepsy. For each type we calculated prevalence and HRU. A distance analysis...

article

Signal detection for vaccine side effects that have not been specified in advance

Alexander M. Walker

Pharmacoepidemiology and Drug Safety > 19 > 3 > 311 - 317

An information‐theoretic definition of similarity proposed by Dekang Lin in 1998 appears to have attractive properties for identifying medically similar cases in a large database. Examination of similar cases that appear following vaccination may provide a way of detecting previously unexpected associations. A key element here is the inclusion of shared time‐since‐vaccination as a dimension of similarity...

article

Risk of hyperkalemia in women taking ethinylestradiol/drospirenone and other oral contraceptives

Jeanne Loughlin, John D. Seeger, P. Mona Eng, Marie Foegh, more

Contraception > 2008 > 78 > 5 > 377-383

The oral contraceptive ethinyl estradiol 0.03 mg/drospirenone 3 mg (EE/DRSP) contains a progestin component that possesses potassium-sparing diuretic activity similar to spironolactone. We sought to determine whether EE/DRSP use might lead to adverse effects possibly attributable to hyperkalemia.This was a matched cohort study in which we identified oral contraceptive (OC) initiators between July...

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INFONA - science communication portal

Search results for: Alexander M. Walker

Stratified analysis in comparative effectiveness studies that emulate randomized trials

The acute effects of azithromycin use on cardiovascular mortality as compared with amoxicillin–clavulanate in US Veterans

Sequential surveillance for drug safety in a regulatory environment

Reuse of data sources to evaluate drug safety signals: When is it appropriate?

A Case Study of the Incremental Utility for Disease Identification of Natural Language Processing in Electronic Medical Records

For drug-induced carcinogenesis, the observations are the hypothesis

Computer-assisted expert case definition in electronic health records

Identifying health outcomes in healthcare databases

Acute Nonarteritic Anterior Ischemic Optic Neuropathy and Exposure to Phosphodiesterase Type 5 Inhibitors

Characteristics of study design and elements that may contribute to the success of electronic safety monitoring systems

Cardiac mortality in users of olmesartan, other angiotensin‐receptor blockers and angiotensin‐converting enzyme inhibitors

Matching on provider is risky

Risk of Guillain–Barré syndrome after meningococcal conjugate vaccination

Transarticular Facet Screw Stabilization and Dorsal Laminectomy in 26 Dogs with Degenerative Lumbosacral Stenosis with Instability

An Event‐Based Approach for Comparing the Performance of Methods for Prospective Medical Product Monitoring

Identification of esophageal cancer in the General Practice Research Database

Orthogonal predictions: follow‐up questions for suggestive data

Health care resource utilization in patients with active epilepsy

Signal detection for vaccine side effects that have not been specified in advance

Risk of hyperkalemia in women taking ethinylestradiol/drospirenone and other oral contraceptives

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