How to write statistical analysis section in medical research

Increases in amyloid-β42 slow cognitive and clinical decline in Alzheimer's disease trials

Positive effects of new anti-amyloid-β (Aβ) monoclonal antibodies in Alzheimer's disease (AD) have been attributed to brain amyloid reduction. However, most anti-Aβ antibodies also increase the CSF levels of the 42-amino acid isoform (Aβ42). We evaluated the associations of changes in CSF Aβ42 and brain Aβ-PET with cognitive and clinical end points in randomized trials of anti-Aβ drugs that lowered (β- and γ-secretase inhibitors) or increased CSF Aβ42 levels (anti-Aβ monoclonal antibodies) to test the hypothesis that post-treatment increases in CSF Aβ42 levels are independently associated with cognitive and clinical outcomes. From long-term (≥12 months) randomized placebo-controlled clinical trials of anti-Aβ drugs published until November 2023, we calculated the post-treatment versus baseline difference in ADAS-Cog (cognitive subscale of the Alzheimer's Disease Assessment Scale) and CDR-SB (Clinical Dementia Rate-Sum of Boxes) and z-standardized changes in CSF Aβ42 and Aβ-PET Centiloids (CL). We estimated the effect size [regression coefficients (RCs) and confidence intervals (CIs)] and the heterogeneity (I2) of the associations between AD biomarkers and cognitive and clinical end points using random-effects meta-regression models. We included 25 966 subjects with AD from 24 trials. In random-effects analysis, increases in CSF Aβ42 were associated with slower decline in ADAS-Cog (RC: -0.55; 95% CI: -0.89, -0.21, P = 0.003, I2 = 61.4%) and CDR-SB (RC: -0.16; 95% CI: -0.26, -0.06, P = 0.002, I2 = 34.5%). Similarly, decreases in Aβ-PET were associated with slower decline in ADAS-Cog (RC: 0.69; 95% CI: 0.48, 0.89, P < 0.001, I2 = 0%) and CDR-SB (RC: 0.26; 95% CI: 0.18, 0.33, P < 0.001, I2 = 0%). Sensitivity analyses yielded similar results. Higher CSF Aβ42 levels after exposure to anti-Aβ drugs are independently associated with slowing cognitive impairment and clinical decline. Increases in Aβ42 may represent a mechanism of potential benefit of anti-Aβ monoclonal antibodies in AD.

Efficacy of ultrasonography and color-Doppler for early prediction of hemodialysis arteriovenous fistula unassisted maturation

BACKGROUND

Arteriovenous fistula (AVF) failure is a prevalent concern for patients with end-stage kidney disease on hemodialysis. Recognizing the efficacy of ultrasound Doppler in post-operative AVF evaluation, this study sought to discern the predictive capabilities of various ultrasonographic and color-Doppler metrics for early AVF outcomes.

METHODS

This single-center, prospective cohort study spanned 1 year and, post ethical clearance, included all patients who underwent native AVF creation surgery and were subsequently referred for standard post-operative ultrasound Doppler assessment. Parameters such as fistula size, cephalic vein area and diameter, and AVF flow velocity and rates were assessed on post-operative day 2, week 2, and week 6. These initial findings were juxtaposed with later outcomes to determine unassisted AVF results.

RESULTS

Of the initial cohort of 40 patients, 75% encountered AVF failure, whereas 25% realized successful unassisted AVF maturation. A notable observation was the significant variance in AVF flow rates as early as post-operative day 2. A threshold of >246 ml/min was indicative of successful unassisted AVF maturation, leading to a sensitivity of 80% and a specificity of 70%. Although the cephalic vein diameter on post-operative day 2 lacked a robust association with AVF outcomes, a cut-off of >3.4 mm, when combined with flow rate testing, augmented the cumulative sensitivity to 92%.

CONCLUSION

Ultrasound Doppler stands out as a valuable quantitative imaging modality, adept at prognosticating AVF outcomes from as early as post-operative day 2. In particular, a flow rate exceeding 246 ml/min and a cephalic vein diameter surpassing 3.4 mm are salient indicators for the early prediction of successful AVF outcomes.

Enhancing CRC Screening in a Predominantly Hispanic Community: Effectiveness of 1-Day vs. 3-Day Stool-Based Testing Kits

Colorectal cancer (CRC) is the leading cause of cancer-related mortality among U.S. Hispanics, with screening proven to decrease both incidence and mortality. Despite rising CRC screening rates in the U.S., Hispanic participation remains disproportionately low. Stool-based tests, particularly popular for reaching underserved populations, may enhance screening adherence. This study evaluates the performance of a 1-day versus a 3-day stool-based testing kit in improving screening completion rates and reducing the need for reminder calls in a Hispanic community along the U.S.-Mexico border. In our quasi-experimental observational study, participants aged 45-75 years who were uninsured or underinsured and overdue for CRC screening were recruited. They received colorectal cancer education and no-cost stool-based screening facilitated by promotoras. Participants were randomly assigned to receive a 1-day or 3-day Fecal Immunochemical Test (FIT) kit. The promotoras swapped FIT kit distribution roles midway through the study period to mitigate performance bias. Our analysis covered 6,660 FITs-3,067 using the 3-day kit and 3,593 with the 1-day kit. Results indicated a higher return rate for the 1-day FIT kit (61.3% vs. 58.7%, adjusted odds ratio [aOR] = 1.22, p < 0.001), fewer reminders needed (69.7% vs. 78.1%, aOR = 0.65, p < 0.001), and lower abnormal FIT results (5.3% vs. 8.1%, aOR = 0.61, p < 0.001). Conclusively, the 1-day FIT kit required fewer reminders and significantly improved return rates, suggesting it may be a more effective option for increasing CRC screening completion among hard-to-reach Hispanic populations.

Tips and tricks for writing a manuscript to publish in a biomedical journal

Science barely exists until it is published. It is only then that the information surpasses the limits of the author and can be shared by the scientific community. Although scientific articles must follow a rigidly defined structure, there is still room to tell a fascinating story, one that clearly conveys the science and is, at the same time, enjoyable for the reader. To do this, we must use the attributes that characterize good scientific style, with simple, clear, precise, direct, rigorous, and consistent language. Authorship implies authenticity and authority, and considering a researcher as an author entails rights and responsibilities. Scientific writing is not easy, it requires patience and practice; learning to write well is a lifelong task. With the philosophy that most of the qualities required to proficiently write a scientific article depend on attitude, and can be learned and improved upon, in this manuscript we will share with the reader a series of recommendations (based on our own experiences, both positive and negative), which we consider important for writing and successfully publishing. We will focus on the so-called «original» articles (as opposed to review articles, although many of the recommendations presented are applicable to both). Our main purpose is to encourage researchers to take the necessary step and face the challenge of becoming authors of their own scientific articles and successfully publishing their research.

Racial/ethnic differences in the clinical presentation and survival of breast cancer by subtype

Background

Breast cancer (BC) affects racial and ethnic groups differently, leading to disparities in clinical presentation and outcomes. It is unclear how Hispanic ethnicity affects BC outcomes based on geographic location and proximity to the United States (U.S.)/Mexico border. We hypothesized that the impact of race/ethnicity on BC outcomes depends on geographic location and country of origin within each BC subtype.

Methods

We analyzed BC data from the Texas Cancer Registry by race/ethnicity/birthplace according to BC subtype (luminal A/luminal B/human epidermal growth factor receptor 2 [HER2]/triple-negative breast cancer[TNBC]). Other covariates included age, geographic location (U.S., Mexico), residency (border, non-border), treatments, and comorbidities. Crude and adjusted effects of race/ethnicity and birthplace on overall survival (OS) were analyzed using Cox regression methods.

Results

Our analysis of 76,310 patient records with specific BC subtypes revealed that Hispanic and non-Hispanic Black (NHB) patients were diagnosed at a younger age compared with non-Hispanic White (NHW) patients for all BC subtypes. For the 19,748 BC patients with complete data on race/ethnicity/birthplace/residency, Hispanic patients had a higher mortality risk in the Luminal A subtype, regardless of birthplace, whereas U.S.-born Hispanics had a higher risk of death in the TNBC subtype. In contrast, NHB patients had a higher mortality risk in the Luminal A and HER2 subtypes. Residence along the U.S./Mexico border had little impact on OS, with better outcomes in Luminal A patients and worse outcomes in Luminal B patients aged 60-74 years.

Conclusion

Race/ethnicity, geographic birth location, and residency were significant predictors of survival in BC. Migration, acculturation, and reduced healthcare access may contribute to outcome differences.

Associations of sex hormone ratios with metabolic syndrome and inflammation in US adult men and women

Background

Sex hormones play a critical role in sex differences and cardiovascular disease risk associated with metabolic syndrome (MS) and inflammation. However, the associations of sex hormone ratios with metabolic and inflammatory markers are unclear according to sex and age differences. We evaluated the associations of sex hormone ratios with MS and inflammation among males and females.

Methods

A retrospective cross-sectional study was conducted by including all adults from the National Health and Nutrition Examination Survey cycles 2013-2016 and excluding any pregnant women, heart disease, diabetes, and those currently taking insulin. MS was defined using the National Cholesterol Education Program criteria and a high-sensitivity C-reactive protein (CRP) level>3 mg/L was defined as a high CRP. Measures of MS components and CRP concentrations were also analyzed. The primary exposures were testosterone to estradiol (excess androgen index), testosterone to sex hormone-binding globulin (free androgen index), and estradiol to sex hormone-binding globulin (free estradiol index). The adjusted associations were summarized with a relative risk (RR) and 95% confidence interval (CI).

Results

This study included 9167 subjects with 4360 males and 4807 females. Increases in free estradiol index were positively associated with MS (RR=1.48; 95%CI: 1.39, 1.58; RR=1.31; 95%CI: 1.22, 1.40) and high CRP (RR=1.49; 95%CI: 1.25, 1.77; RR=1.26; 95%CI: 1.06, 1.50) in men with age<50 years and age≥50 years, respectively. Similarly, higher free estradiol index was also robustly associated with increased prevalence of MS (RR=1.22; 95%CI: 1.15, 1.28) and high CRP (RR=1.68; 95%CI: 1.48, 1.90) in women with age ≥50 years. Among women with age<50 years, a higher free androgen index was associated with MS (RR=1.34; 95%CI: 1.25, 1.42) and high CRP (RR=1.13; 95%CI: 1.02, 1.25). These associations were unchanged even after adjusting for all sex hormones.

Conclusion

Free estradiol index was consistently and positively associated with MS and high CRP in males of all ages and older females. Free androgen index was positively associated with MS and high CRP in females with age<50 years.

Quality reporting of randomized controlled trials on SGLT2 inhibitors for heart failure: a comprehensive assessment

Randomised controlled trials (RCTs) provide clinicians with the best evidence of the effectiveness of an intervention, and complete and transparent trial reports help to critically assess and use trial results. The objective of our study was to assess the quality of reporting in RCTs of sodium-glucose co-transporter protein 2 (SGLT2) inhibitors for heart failure (HF) and identify factors associated with improved reporting quality. Two researchers conducted a comprehensive search in four databases (PubMed, Web of Science, EMBASE, and Cochrane). The quality of each report was assessed using a 25-point Overall Quality Score (OQS) based on the guidelines provided in the 2010 Consolidated Standards for Reporting of Trials (CONSORT) statement. We included a total of 58 relevant RCTs. The median OQS in the 2010 CONSORT statement was 15 (range 7.5-24). The missing items were primarily found in the 'Methods' and 'Results' sections of the 2010 CONSORT statement. Multivariate regression modeling revealed that a more recent publication year, high impact factor, and large sample size were significant predictors of OQS improvement. The findings suggest that the overall quality of reported RCTs of SGLT2 inhibitors in HF is unsatisfactory, which reduces their potential usefulness.

COVID-19-related mortality in Texas border counties vs non-border counties

The state of Texas ranked second in total cases of coronavirus disease 2019 (COVID-19) in the United States during the pandemic. Counties near the US-Mexico border were severely impacted by the pandemic. Mortality and long-term consequences from COVID-19 are associated with comorbidities, illness severity, and patient demographics. However, differences in outcomes between border and non-border counties are unknown. In this retrospective observational study, data were obtained for analysis from the Texas hospital inpatient discharge public use data file from 2020 to 2021 for adult patients with COVID-19 based on the associated international classification of disease 10 codes. Patients were categorized into border or non-border counties. The clinical outcomes included mortality, length of stay, mortality risk, illness severity, and intensive care unit (ICU) or critical care unit (CCU) admissions. Cost differences between border and non-border counties were analyzed. Age, gender, race, ethnicity, admission type, location, and year of diagnosis were covariates. A total of 1,745,312 patients were included in this analysis. 25% of COVID-19 patients admitted in Texas were from border counties. Patient mortality was 5.35% in border counties compared to 3.87% in non-border counties (p = 0.003). In border counties, 36.51% and 32.96% of patients required ICU and CCU admissions compared to 32.96% and 10.72%, respectively in non-border counties. Border counties had significantly higher risk of mortality (relative risk (RR) = 1.26; 95% CI: 1.09-1.46, p = 0.002), ICU admission (RR = 1.15; 95% CI: 1.15; 95% CI: 1.01-1.32, p = 0.038), CCU admission (RR = 2.87; 95% CI: 1.93, 4.27, p < 0.001), and ICU/CCU admission (RR = 1.28; 95% CI: 1.10, 1.48, p < 0.001) which reflects health disparities in the management of COVID-19 in border counties of Texas.

A template for the authoring of statistical analysis plans

A number of principal investigators may have limited access to biostatisticians, a lack of biostatistical training, or no requirement to complete a timely statistical analysis plan (SAP). SAPs completed early will identify design or implementation weak points, improve protocols, remove the temptation for p-hacking, and enable proper peer review by stakeholders considering funding the trial. An SAP completed at the same time as the study protocol might be the only comprehensive method for at once optimizing sample size, identifying bias, and applying rigor to study design. This ordered corpus of SAP sections with detailed definitions and a variety of examples represents an omnibus of best practice methods offered by biostatistical practitioners inside and outside of industry. The article presents a protocol template for clinical research design, enabling statisticians, from beginners to advanced.

Common Variables That Influence Sepsis Mortality in Mice

Introduction

Sepsis is characterized by a dysregulated host immune response to infection, leading to organ dysfunction and a high risk of death. The cecal ligation and puncture (CLP) mouse model is commonly used to study sepsis, but animal mortality rates vary between different studies. Technical factors and animal characteristics may affect this model in unanticipated ways, and if unaccounted for, may lead to serious biases in study findings. We sought to evaluate whether mouse sex, age, weight, surgeon, season of experiments, and timing of antibiotic administration influenced mortality in the CLP model.

Methods

We created a comprehensive dataset of C57BL/6J mice that had undergone CLP surgery within our lab during years 2015-2020 from published and unpublished studies. The primary outcome was defined as the time from sepsis induction to death or termination of study (14 days). The Log rank test and Cox regression models were used to analyze the dataset. The study included 119 mice, of which 43% were female, with an average age of 12.6 weeks, an average weight of 25.3 g. 38 (32%) of the animals died.

Results

In the unadjusted analyses, experiments performed in the summer and higher weight predicted a higher risk of mortality. In the stratified Cox model by sex, summer season (adjusted hazard ratio [aHR]=5.61, p=0.004) and delayed antibiotic administration (aHR=1.46, p=0.029) were associated with mortality in males, whereas higher weight (aHR=1.52, p=0.005) significantly affected mortality in females. In addition, delayed antibiotic administration (HR=1.42, p=0.025) was associated with mortality in the non-summer seasons, but not in the summer season.

Discussion

In conclusion, some factors specific to sex and season have a significant influence on sepsis mortality in the CLP model. Consideration of these factors along with appropriate group matching or adjusted analysis is critical to minimize variability beyond the experimental conditions within a study.

Association of Exposure to Phthalate Metabolites With Sex Hormones, Obesity, and Metabolic Syndrome in US Women

IMPORTANCE

Obesity and metabolic syndrome are highly prevalent among the US population and are associated with the dysregulation of sex hormones. An increase in obesity and metabolic syndrome may also be associated with exposure to phthalates. The association of exposure to phthalate metabolites with sex hormones and metabolic health has been understudied in the female population.

OBJECTIVE

To evaluate the association between exposure to common phthalate metabolites with total testosterone (TT) levels, sex hormone-binding globulin (SHBG) levels, obesity, and metabolic syndrome among women.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study used data collected from the National Health and Nutrition Examination Survey during 2013 to 2016. Female participants aged 15 years or older with urinary profiles containing common phthalate metabolites were included in this study. Statistical analyses were performed from March 15, 2021, to April 30, 2022.

EXPOSURES

Urinary concentrations of phthalate metabolites were classified into tertiles, and the lowest tertile was used as a reference category. The concentrations of phthalate metabolites and their composite scores based on clustering were also used in the analysis.

MAIN OUTCOMES AND MEASURES

Serum concentrations of TT and SHBG were dichotomized into high TT levels (>46 ng/dL [to convert to nanomoles per liter, multiply by 0.0347] for age <50 years and >32 ng/dL for age ≥50 years) and low SHBG levels (<2.85 μg/mL [to convert to nanomoles per liter, multiply by 10.53]) as established for the female population. Obesity was defined as a body mass index of 30 or more (calculated as weight in kilograms divided by height in meters squared), and metabolic syndrome was defined using the National Cholesterol Education Program criteria. The serum concentrations of TT and SHBG were also included in the validation analyses. Modified Poisson models were used to estimate the adjusted relative risk (RR) with 95% CIs for the associations.

RESULTS

Among the 2004 women included in this study, the mean (SD) age was 46.6 (18.5) years (14.7% Hispanic participants, 62.7% non-Hispanic White participants, and 13.2% non-Hispanic Black participants; 17.4% of participants were born outside the US [weighted percentages]; 230 (11.8%) had high TT levels, 210 (10.4%) had low SHBG levels, 825 (39.8%) had obesity, and 965 (45.5%) had metabolic syndrome (weighted percentages). Of the 13 phthalate metabolites, 8 had the highest tertile level greater than 6.2 ng/mL (range, 0.5-75.2 ng/mL). High levels of exposure to mono(2-ethyl-5-carboxypentyl) phthalate (RR, 1.84 [95% CI, 1.33-2.54]), mono(2-ethyl-5-oxohexyl) phthalate (RR, 1.77 [95% CI, 1.21-2.59]), mono(2-ethyl-5-hydroxyhexyl) phthalate (RR, 1.94 [95% CI, 1.34-2.81]), and monobenzyl phthalate (RR, 1.75 [95% CI, 1.21-2.54]) were associated with low SHBG levels but not with high TT levels. High levels of exposure to some of these metabolites were also associated with obesity and metabolic syndrome. Most associations were specific to premenopausal or postmenopausal women.

CONCLUSIONS AND RELEVANCE

In this cross-sectional study, exposure to certain phthalate metabolites could be associated with low SHBG levels, obesity, and metabolic syndrome depending on menopausal status.

Disparities in Metabolic Conditions and Cancer Characteristics among Hispanic Women with Breast Cancer: A Multi-Institutional Study

While the associations of common metabolic conditions with ethnicity have been previously described, disparity among Hispanic individuals based on country of origin is understudied. This multi-institutional analysis explored the prevalence of metabolic conditions and their association with cancer subtypes among Mexican and non-Mexican Hispanics. After IRB approval, we conducted a cross-sectional study at two academic medical centers with a significant Hispanic patient population (Texas Tech University Health Sciences Center, El Paso, TX (TTUHSC-EP) and Cleveland Clinic Florida in Weston, FL (CCF)). A total of n = 1020 self-identified Hispanic patients with breast cancer consecutively diagnosed between 2005 and 2014 were selected from the two institutional databases. Comparisons between Mexican and Non-Mexican Hispanics revealed variations in tumor types and metabolic conditions. Mexican Hispanics were found to have a higher prevalence of diabetes mellitus (27.8% vs. 14.2%, p < 0.001), obesity (51.0% vs. 32.5%, p < 0.001), and ductal carcinoma type (86.6 vs. 73.4%, p < 0.001). On the other hand, hormone-receptor-positive breast cancer was more common in non-Mexicans, while Mexicans had more triple-negative breast cancer, especially in premenopausal women. In addition to highlighting these variations among Hispanic patients with breast cancer, this study supports a more focused approach to addressing obesity and other metabolic conditions prevalent in the Hispanic population with breast cancer. Moreover, Hispanic individuals with breast cancer are diverse and should not be lumped under one category without reference to their country of origin regarding the impact of race and ethnicity.