Natasa M. Milic

Beyond Bar and Line Graphs: Time for a New Data Presentation Paradigm

Figures in scientific publications are critically important because they often show the data supporting key findings. Our systematic review of research articles published in top physiology journals (n = 703) suggests that, as scientists, we urgently need to change our practices for presenting continuous data in small sample size studies. Papers rarely included scatterplots, box plots, and histograms that allow readers to critically evaluate continuous data. Most papers presented continuous data in bar and line graphs. This is problematic, as many different data distributions can lead to the same bar or line graph. The full data may suggest different conclusions from the summary statistics. We recommend training investigators in data presentation, encouraging a more complete presentation of data, and changing journal editorial policies. Investigators can quickly make univariate scatterplots for small sample size studies using our Excel templates.

Impaired Flow-Mediated Dilation Before, During, and After Preeclampsia A Systematic Review and Meta-Analysis

Endothelial dysfunction is believed to play a critical role in preeclampsia; however, it is unclear whether this dysfunction precedes the pregnancy or is caused by pathophysiological events in early pregnancy. It is also unclear for how long vascular dysfunction may persist postpartum and whether it represents a mechanism linking preeclampsia with future cardiovascular disease. Our objective was to determine whether women with preeclampsia had worse vascular function compared with women who did not have preeclampsia by performing a systematic review and meta-analysis of studies that examined endothelial dysfunction using flow-mediated dilation. We included studies published before May 29, 2015, that examined flow-mediated dilation before, during, or after preeclampsia. Differences in flow-mediated dilation between study groups were evaluated by standardized mean differences. Out of 610 abstracts identified through PubMED, EMBASE, and Web of Science, 37 studies were eligible for the meta-analysis. When compared with women who did not have preeclampsia, women who had preeclampsia had lower flow-mediated dilation before the development of preeclampsia (≈20–29 weeks gestation), at the time of preeclampsia, and for 3 years postpartum, with the estimated magnitude of the effect ranging between 0.5 and 3 standard deviations. Similar effects were observed when the analysis was limited to studies that excluded women with chronic hypertension, smokers, or both. Vascular dysfunction predates preeclampsia and may contribute to its pathogenesis. Future studies should address whether vascular changes that persist after preeclamptic pregnancies may represent a mechanistic link with increased risk for future cardiovascular disease.

Reinventing Biostatistics Education for Basic Scientists

Numerous studies demonstrating that statistical errors are common in basic science publications have led to calls to improve statistical training for basic scientists. In this article, we sought to evaluate statistical requirements for PhD training and to identify opportunities for improving biostatistics education in the basic sciences. We provide recommendations for improving statistics training for basic biomedical scientists, including: 1. Encouraging departments to require statistics training, 2. Tailoring coursework to the students’ fields of research, and 3. Developing tools and strategies to promote education and dissemination of statistical knowledge. We also provide a list of statistical considerations that should be addressed in statistics education for basic scientists.

From Static to Interactive: Transforming Data Visualization to Improve Transparency.

Data presentation for scientific publications in small sample size studies has not changed substantially in decades. It relies on static figures and tables that may not provide sufficient information for critical evaluation, particularly of the results from small sample size studies. Interactive graphics have the potential to transform scientific publications from static reports of experiments into interactive datasets. We designed an interactive line graph that demonstrates how dynamic alternatives to static graphics for small sample size studies allow for additional exploration of empirical datasets. This simple, free, web-based tool (http://statistika.mfub.bg.ac.rs/interactive-graph/) demonstrates the overall concept and may promote widespread use of interactive graphics.

Impaired Cognition and Brain Atrophy Decades After Hypertensive Pregnancy Disorders

Background—Hypertensive pregnancy disorders have been associated with subjective cognitive complaints or brain white-matter lesions 5 to 10 years after the hypertensive pregnancy. The long-term effects of hypertensive pregnancies on brain structure and cognitive function remain unknown. Methods and Results—This study included 1279 women who participated in the Family Blood Pressure Project Genetic Epidemiology Network of Arteriopathy (GENOA) study. As part of the ancillary Genetics of Microangiopathic Brain Injury (GMBI) study, a neurocognitive battery was administered; 1075 also had a brain magnetic resonance imaging. A history of a hypertensive pregnancy disorder was obtained by a self-report using a validated questionnaire. Linear models fit with generalized estimating equations were used to assess the association between hypertensive pregnancy disorders and cognition, adjusting for age, race, education, body mass index, smoking, current hypertension, hypertension duration, and family history of hypertension. Regression models for the brain magnetic resonance imaging outcomes also were adjusted for total intracranial volume. Women with histories of hypertensive pregnancy disorders performed worse on all measures of processing speed (Digital Symbol Substitution Test [mean score, 41.2 versus 43.4; P=0.005], Trail Making Test Part A [mean seconds, 45.1 versus 42.2; P=0.035], and Stroop [mean score, 173.9 versus 181.0; P=0.002]) and had smaller brain volumes compared with women with histories of normotensive pregnancies (286 versus 297; P=0.023). Conclusions—Hypertensive pregnancy disorders are associated with worse performance on tests of processing speed and smaller brain volumes decades later. Population-based studies are needed to provide critical insight as to the contribution of hypertensive pregnancies to risk of cognitive decline and dementia.

Methodological differences account for inconsistencies in reported free VEGF concentrations in pregnant rats

Free vascular endothelial growth factor (VEGF) is undetectable in plasma during human pregnancy. However, studies examining pregnant rats have reported both low (8-29 pg/ml) and high (527-1,030 pg/ml) free VEGF. These discrepancies cast uncertainty over the use of rat models to study angiogenic factors in pregnancy and preeclampsia. This study investigates methodological factors that may explain these discrepancies. Plasma VEGF in nonpregnant, day 7 pregnant, and day 19 pregnant rats was measured using rat and mouse ELISAs (R&D Systems). The rat ELISA detected VEGF in plasma from nonpregnant rats but not in plasma from day 19 pregnant rats. The mouse ELISA detected higher VEGF concentrations than the rat ELISA in every sample tested. This discrepancy was greater in day 19 pregnant rats (median: 2,273 vs. 0 pg/ml) than in nonpregnant (97 vs. 20 pg/ml) and day 7 pregnant (66 vs. 2 pg/ml) rats. Recovery of recombinant rat VEGF (rrVEGF) spiked into plasma from nonpregnant and day 7 pregnant rats was high for the rat ELISA (82-105%) but low for the mouse ELISA (17-22%). The rat ELISA did not recover rrVEGF in plasma from day 19 pregnant rats, suggesting that this ELISA measures free VEGF. The use of the rat versus mouse ELISA likely explains the differences in reported VEGF concentrations in pregnant rats. While the rat ELISA appears to measure free VEGF, plasma concentrations in nonpregnant and pregnant rats are below the assay sensitivity limit. As most previous studies of pregnant rats used the mouse VEGF ELISA, these data should be interpreted cautiously.

Preclinical atherosclerosis at the time of pre‐eclamptic pregnancy and up to 10 years postpartum: systematic review and meta‐analysis

Pre‐eclampsia (PE) is a pregnancy‐specific hypertensive disorder that has been associated with cardiovascular risk factors and vascular changes, such as acute atherosis in placental blood vessels, similar to early‐stage atherosclerosis. The objective of this study was to determine whether women with PE have increased atherosclerotic burden, as determined by the carotid intima–media thickness (CIMT), compared with women without PE.

Transparent reporting for reproducible science

Tracey L. Weissgerber, Vesna D. Garovic, Stacey J. Winham, Natasa M. Milic, and Eric M. Prager* Division of Nephrology & Hypertension, Mayo Clinic, 200 First Street SW, Rochester, Minnesota, 55905 Division of Biomedical Statistics & Informatics, Mayo Clinic, 200 First Street SW, Rochester, Minnesota, 55905 Department of Medical Statistics & Informatics, Medical Faculty, University of Belgrade, Dr. Subotica 15, Belgrade, Serbia, 11000 John Wiley & Sons, Inc., 111 River St, Hoboken, New Jersey, 07030

Development and validation of multivariable predictive model for thromboembolic events in lymphoma patients.

Lymphoma patients are at increased risk of thromboembolic events but thromboprophylaxis in these patients is largely underused. We sought to develop and validate a simple model, based on individual clinical and laboratory patient characteristics that would designate lymphoma patients at risk for thromboembolic event. The study population included 1,820 lymphoma patients who were treated in the Lymphoma Departments at the Clinics of Hematology, Clinical Center of Serbia and Clinical Center Kragujevac. The model was developed using data from a derivation cohort (nu2009=u20091,236), and further assessed in the validation cohort (nu2009=u2009584). Sixty‐five patients (5.3%) in the derivation cohort and 34 (5.8%) patients in the validation cohort developed thromboembolic events. The variables independently associated with risk for thromboembolism were: previous venous and/or arterial events, mediastinal involvement, BMI>30 kg/m2, reduced mobility, extranodal localization, development of neutropenia and hemoglobin levelu2009<u2009100g/L. Based on the risk model score, the population was divided into the following risk categories: low (score 0‐1), intermediate (score 2‐3), and high (score >3). For patients classified at risk (intermediate and high‐risk scores), the model produced negative predictive value of 98.5%, positive predictive value of 25.1%, sensitivity of 75.4%, and specificity of 87.5%. A high‐risk score had positive predictive value of 65.2%. The diagnostic performance measures retained similar values in the validation cohort. Developed prognostic Thrombosis Lymphoma – ThroLy score is more specific for lymphoma patients than any other available score targeting thrombosis in cancer patients. Am. J. Hematol. 91:1014–1019, 2016.

Carotid Artery Intima-Media Thickness and Subclinical Atherosclerosis in Women With Remote Histories of Preeclampsia: Results From a Rochester Epidemiology Project-Based Study and Meta-analysis

OBJECTIVEnTo measure carotid artery intima-media thickness (CIMT), a marker of subclinical atherosclerosis, in postmenopausal women with and without histories of preeclampsia and to synthesize these results with those from prior studies of CIMT performed 10 or more years after preeclamptic pregnancies.nnnPATIENTS AND METHODSnForty women (median age, 59 years) with histories of preeclampsia and 40 with histories of normotensive pregnancy (confirmed by medical record review) were selected from women who resided and gave birth in Olmsted County, Minnesota, between January 1, 1976, and December 31, 1982. The participants were identified and recruited in 2014-2015, and CIMT was measured by B-mode ultrasonography. Meta-analysis included CIMT studies that were performed 10 or more years after preeclamptic pregnancies and which were identified through PubMed, EMBASE, and Web of Science. Heterogeneity was assessed using the I2 statistic. Standardized mean difference was used as a measure of effect size.nnnRESULTSnCarotid artery intima-media thickness, expressed as a median (interquartile range), was greater in the preeclamptic than in the normotensive group (0.80 mm [0.75-0.85 mm] vs 0.73 mm [0.70-0.78]; P=.004); the odds of having CIMT higher than threshold (0.77 mm) was statistically significant after adjusting for confounding factors (odds ratio, 3.17; 95% CI, 1.10-9.14). A meta-analysis of 10 studies conducted 10 or more years post partum included 813 women with and 2874 without histories of preeclampsia. Carotid artery intima-media thickness was greater among women with histories of preeclampsia, with a standardized mean difference of 0.18 and 95% CI of 0.05 to 0.30 mm (P=.004).nnnCONCLUSIONnAmong women with histories of preeclampsia, CIMT may identify those with subclinical atherosclerosis, thus offering an opportunity for early intervention.