Best (but oft-forgotten) practices: propensity score methods in clinical nutrition research

Association of changes in HerQLes scores with objective hernia outcomes: an analysis of the ACHQC database

BACKGROUND

There are both objective and subjective measures of success following ventral hernia repair (VHR). Using the Abdominal Core Health Quality Collaborative (ACHQC) database, we sought to determine if there is an association between 30-day wound events (objective) and changes in the hernia-related quality-of-life (HerQLes) scores, (subjective). We hypothesized that patients who do not experience a 30-day wound event have a greater improvement in their HerQLes score over the short-term.

METHODS

All adult patients who underwent VHR with 30-day follow-up data available between 2013 and 2022 were identified within the ACHQC database. The 30-day wound events included surgical site infection (SSI), surgical site occurrence (SSO), and SSO requiring procedural intervention (SSOPI). The association between 30-day wound events and changes in HerQLes scores was measured using propensity matched score analysis. Further, regression analysis was used to determine if an improvement in HerQLes score at 30-days postoperatively was associated with the likelihood of experiencing a 30-day wound event.

RESULTS

Following a 3:1 matched analysis, 17,796 patients were available for analysis; 4449 (25%) patients experienced a 30-day wound event. The most common SSI was a superficial SSI and the most common SSO was a seroma. A 10-point improvement in the HerQLes score was statistically associated with a 3% decrease in SSI and a 4% decrease in the odds of experiencing an SSO. While not statistically significant, a 10-point improvement in the HerQLes score was associated with a 2.4% decrease in the odds of experiencing an SSOPI.

CONCLUSIONS

Subjective and objective measures of success following VHR seem to be correlated with one another over the short-term. Additional studies are needed to determine if this correlation exists with other subjective and objective measures of success and to determine if these correlations persist over the long-term. If present, these associations may help to guide patient counseling as experiencing a postoperative wound event following ventral hernia repair may not be detrimental to their quality-of-life over the long-term.

The potential causal effect of the pre-pregnancy dietary phytochemical index on gestational diabetes mellitus: a prospective cohort study

BACKGROUND

Phytochemicals are non-nutritive bioactive compounds with beneficial effects on the metabolism of glucose. This study aimed to clarify the possible causal effect of the pre-pregnancy dietary phytochemical index (DPI) on gestational diabetes mellitus (GDM).

METHODS

In this prospective cohort study 1,856 pregnant women aged 18-45 years who were in their first trimester, were recruited and followed up until delivery. The dietary intakes of participants were examined using an interviewer-administered validated 168-item semi-quantitative food frequency questionnaire (FFQ). Inverse probability weighting (IPW) of propensity scores (PS), estimated from the generalized boosted model (GBM) were used to obtain a adjusted risk ratio (aRR) for potential confounders.

RESULTS

During the follow-up period, 369 (19.88%) women were diagnosed with GDM. DPI scores ranged from 6.09 to 89.45. There was no association between DPI scores and GDM (aRR: 1.01, 95% confidence interval [CI]: 0.92, 1.08; p trend = 0.922). When comparing DPI quartile 4 (most pro-phytochemical content) to quartile 1 (few phytochemical contents), there was no significant difference between them (aRR: 0.97; 95% CI: 0.75, 1.25; p = 0.852). Also, there was no significant difference between DPI quartile 3 and quartile 1 (aRR: 1.04; 95% CI: 0.81, 1.34; p = 0.741) as well as DPI quartile 2 and quartile 1 (aRR: 0.92; 95% CI: 0.71, 1.21; p = 0.593).

CONCLUSIONS

Although this data did not support the association between pre-pregnancy DPI scores and GDM, further cohort studies to ascertain the causal association between them are warranted.

Negative effects of undernutrition on sputum smear conversion and treatment success among retreatment cases in Uganda: A quasi-experimental study

Rationale

The causal relationship between undernutrition and response to anti-tuberculosis (TB) treatment and TB treatment outcomes among people with retreatment TB is understudied.

Objective

To evaluate the effect of undernutrition on treatment success and sputum smear conversion among people with retreatment drug-susceptible TB in Kampala, Uganda.

Methods

We conducted a quasi-experimental study utilizing propensity score weighting among people with retreatment drug-susceptible TB aged ≥ 15 years treated between 2012 and 2022 in Kampala. The primary exposure was undernutrition assessed using the mid-upper arm circumference at the time of TB diagnosis. The primary outcome was treatment success defined as cure or treatment completion at month 6. Sputum smear conversion was the secondary outcome and was measured as a change in sputum smear status from positive to negative at months 2, 5, and 6. We estimated the causal effect of undernutrition on the outcomes using a propensity-score weighted modified Poisson regression model with robust error variance.

Measurements and main results

Of the 605 participants, 432 (71.4 %) were male, 215 (35.5 %) were aged 25-34 years, 427 (70.6 %) had bacteriologically confirmed pulmonary TB, 133 (22.0 %) were undernourished and 398 (65.8 %) achieved treatment success. Of participants with bacteriologically confirmed pulmonary TB, 232 (59.0 %), 327 (59.3 %), and 360 (97.6 %) achieved sputum smear conversion at months 2, 5, and 6, respectively. Undernutrition reduced treatment success (RR 0.42, 95 % CI 0.32-0.55) as well as sputum smear conversion at months 2 (RR 0.45, 95 % CI 0.42-0.49) and 5 (RR 0.46, 95 % CI 0.43-0.51) but not month 6 (RR 0.99, 95 % CI 0.97-1.02).

Conclusion

Undernutrition negatively impacts treatment outcomes. Therefore, nutritional assessment should be an integral component of TB care, with nutritional counseling and support offered to those undernourished to optimize their TB treatment response and outcomes.

Combining social protection interventions for better food security: Evidence from female-headed households in Amhara region, Ethiopia

Ethiopia introduced its flagship poverty-targeted social protection program, the Productive safety net program (PSNP), in 2005 and Community-Based Health Insurance (CBHI) in 2011. Although both programs operate in several districts with some overlaps, evidence is scarce on how these large-scale programs jointly affect the food security of vulnerable groups. This study examines the impacts of a combination of these programs on food security outcomes among female-headed households in a chronically food-insecure and drought-prone district. Cross-sectional data were collected from 365 female-headed households selected through multi-stage sampling technique and analyzed using Inverse-probability-weighted regression adjustment (IPWRA) strategy to assess the effect of the programs on food security. The results show that while 63.6% of sample households are enrolled in CBHI and 48.8% are beneficiaries of PSNP's conditional cash transfer (CCT) component, membership in both social protection programs was 38.9%. The IPWRA analysis finds that inclusion in the CCT combined with CBHI, on average, increased dietary diversity score by 0.918 (95% CI 0.779-1.057) and food consumption score by 0.576 (95% CI 0.464-0.688). It also reduced household food insecurity access scale by 8.658 (95% CI -9.775 - -7.541). In all assessments, a combination of CBHI and CCT always produced results of a larger magnitude than each of CBHI and CCT alone. The findings provide evidence of the potentials of integrating social protection programs to increase food security outcomes among the most vulnerable and marginalized groups in a developing country. In addition, the results have also useful implications to achieve sustainable development goals related to ending hunger and achieving food security among vulnerable groups.

Impact of a Food Skills Course with a Teaching Kitchen on Dietary and Cooking Self-Efficacy and Behaviors among College Students

College students may face barriers to eating healthy foods. Educational interventions providing practical knowledge and skills may help students to overcome financial barriers or other barriers to acquiring, preparing, and consuming healthy foods. We evaluated the association between participation in a semester-long food skills course with an interactive teaching kitchen and dietary and cooking self-efficacy and behaviors. Participants were recruited from course enrollees (intervention) and the general student population (comparison). We assessed differences in pre-post changes in the outcomes between groups using the propensity score weighting and mixed effects linear or Poisson regression. Course participation was associated with improved self-efficacy around cooking (group × time β-coefficient [SE]: 3.25 [0.57], p < 0.0001) and fruit (6.33 [1.19], p < 0.0001), vegetable (5.43 [1.42], p = 0.0002), and whole grain (5.83 [1.40], p < 0.0001) consumption. Course participants reported smaller pre-post decreases in vegetable consumption compared to non-participants (0.35 [0.16], p = 0.03), increased cooking frequency (0.22 [0.10], p = 0.03) and a decreased frequency of skipping meals (-0.47 [0.16], p = 0.003). There were no changes associated with the intervention in the consumption of fruit or whole grains, or in eating out frequency. Participation in a semester-long, personal food skills course with a teaching kitchen may improve self-efficacy, cooking, and vegetable consumption among college students.

Participation in the CenteringPregnancy Program and Pregnancy-Induced Hypertension

INTRODUCTION

CenteringPregnancy emphasizes nutrition, learning, and peer support through a group meeting format in contrast to the standard of prenatal care that maximizes a pregnant patient's time with their provider. It was hypothesized that the program may yield a reduced risk of pregnancy-induced hypertension. In this observational study, authors examined the impacts of the CenteringPregnancy program versus those of standard of prenatal care on pregnancy-induced hypertension.

METHODS

In 2021, birth certificate data were linked to hospital discharge records of women who delivered in obstetric clinics in the Midlands of South Carolina between 2015 and 2019. Logistic regression models were used to estimate the association between CenteringPregnancy participation (n=547) and any pregnancy-induced hypertension and specific pregnancy-induced hypertension diagnoses (gestational hypertension/unspecified hypertension, mild pre-eclampsia, and severe pre-eclampsia/eclampsia). Propensity score techniques (e.g., inverse probability of treatment weighting) were used to adjust for self-selection into the program versus into standard of prenatal care.

RESULTS

CenteringPregnancy participants had higher odds of developing any pregnancy-induced hypertension under all specifications (OR=1.48, 95% CI=1.15, 1.92) and specifically gestational hypertension/unspecified hypertension (OR=1.76, 95% CI=1.28, 2.42) than those in standard of prenatal care. However, CenteringPregnancy participants did not experience significantly higher odds of mild pre-eclampsia (OR=1.06, 95% CI=0.65, 1.78) and severe pre-eclampsia/eclampsia (OR=1.21, 95% CI=0.78, 1.89) compared with standard of prenatal care participants.

CONCLUSIONS

Participation in CenteringPregnancy was associated with higher odds of pregnancy-induced hypertension, particularly gestational hypertension, than participation in standard of prenatal care. Additional research is warranted to definitely rule out selection bias and identify contributing factor(s) that increased pregnancy-induced hypertension despite efforts to improve pregnancy-related health outcomes among CenteringPregnancy participants.

Best (but oft forgotten) statistical practices: Measuring real-world intervention effectiveness using electronic health data

The evidence base supporting the use of most interventions consists primarily of data from randomized controlled trials (RCTs), but how and to whom interventions are delivered in clinical practice may differ substantially from these foundational RCTs. With the increasing availability of electronic health data, it is now feasible to study the "real-world" effectiveness of a wide range of interventions. However, real-world intervention effectiveness studies using electronic health data face many challenges including data quality, selection bias, confounding by indication, and lack of generalizability. In this article, we describe the key barriers to generating high-quality evidence from real-world intervention effectiveness studies and suggest statistical best practices for addressing them.

Nutritional impact of excluding red meat from the Canadian diet

The objective of the study was to examine differences in nutrient intake between consumers and non-consumers of red meat and to assess nutritional adequacy of consumers relative to Recommended Daily Allowance (RDA) in Canada. Matching estimators were used to identify differences in nutrient intake between the two groups. Statistically significant differences were observed in nutrient intake between red meat consumers and non-consumers, including lower daily intake of protein, riboflavin, niacin, vitamin D, and zinc and a higher daily intake of dietary fiber, folate, and magnesium among Canadians who did not consume red meat. Further, red meat consumers and non-consumers had nutrient intakes below RDA for dietary energy, fiber, and calcium. While individuals who did not consume red meat were at increased risk of calcium, vitamin D, energy, and potassium inadequacy, those who consumed red meat were at increased risk of dietary fiber, vitamin A, and magnesium inadequacy.

Impact of community-based health insurance on health services utilisation among vulnerable households in Amhara region, Ethiopia

BACKGROUND

Ethiopia piloted community-based health insurance in 2011, and as of 2019, the programme was operating in 770 districts nationwide, covering approximately 7 million households. Enrolment in participating districts reached 50%, holding promise to achieve the goal of Universal Health Coverage in the country. Despite the government's efforts to expand community-based health insurance to all districts, evidence is lacking on how enrolment in the programme nudges health seeking behaviour among the most vulnerable rural households. This study aims to examine the effect of community-based health insurance enrolment among the most vulnerable and extremely poor households participating in Ethiopia's Productive Safety Net Programme on the utilisation of healthcare services in the Amhara region.

METHODS

Data for this study came from Amhara pilot integrated safety net programme baseline survey in Ethiopia and were collected between December 2018 and February 2019 from 5,398 households. We used propensity score matching method to estimate the impacts of enrolment in community-based health insurance on outpatient, maternal, and child preventive and curative healthcare services utilisation.

RESULTS

Results show that membership in community-based health insurance increases the probabilities of visiting health facilities for curative care in the past month by 8.2 percentage points (95% CI 5.3 to 11.1), seeking care from a health professional by 8.4 percentage points (95% CI 5.5 to 11.3), and visiting a health facility to seek any medical assistance for illness and check-ups in the past 12 months by 13.9 percentage points (95% CI 10.5 to 17.4). Insurance also increases the annual household per capita health facility visits by 0.84 (95% CI 0.64 to 1.04). However, we find no significant effects of community-based health insurance membership on utilisation of maternal and child healthcare services.

CONCLUSIONS

Findings that community-based health insurance increased outpatient services utilisation implies that it could also contribute towards universal health coverage and health equity in rural and informal sectors. The absence of significant effects on maternal and child healthcare services may be due to the free availability of such services for everyone at the public health facilities, regardless of insurance membership. Outpatient services use among insured households is still not universal, and understanding of the barriers to use, including supply-side constraints, will help improve universal health coverage.

Effect of Stenting Strategy on the Outcome in Patients with Non-Left Main Bifurcation Lesions

Previous studies have not compared outcomes between different percutaneous coronary intervention (PCI) strategies and lesion locations in non-left main (LM) bifurcation lesions. We enrolled 2044 patients from a multicenter registry with an LAD bifurcation lesion (n = 1551) or non-LAD bifurcation lesion (n = 493). The primary outcome was target lesion failure (TLF), a composite of cardiac death, myocardial infarction, and target lesion revascularization (TLR). During a median follow-up period of 38 months, non-LAD bifurcation lesions treated with the two-stent strategy, compared with the one-stent strategy, were associated with more frequent TLF (20.7% vs. 6.3%, p < 0.01), TLR (16.7% vs. 4.7%, p < 0.01), and target vessel revascularization (TVR; 18.2% vs. 6.3%, p < 0.01). There was no significant difference in outcome among LAD bifurcation lesions treated with different PCI strategies. The two-stent strategy was associated with a higher risk of TLF (adjusted HR 4.34, CI 1.93−9.76, p < 0.01), TLR (adjusted HR 4.30, CI 1.64−11.27, p < 0.01), and TVR (adjusted HR 5.07, CI 1.69−9.74, p < 0.01) in the non-LAD bifurcation lesions. The planned one-stent strategy is preferable to the two-stent strategy for the treatment of non-LAD bifurcation lesions.

Effect of the COVID-19 pandemic restrictions on outcomes of HIV care among adults in Uganda

Uganda enforced several stringent restrictions such as night-time curfews, travel bans, school closure, and physical and social distancing among others that constituted a national lockdown to prevent the spread of the Coronavirus disease 2019 (COVID-19). These restrictions disrupted the delivery of health services but the impact on outcomes of human immunodeficiency virus (HIV) care has not been rigorously studied. We evaluated the effect of the COVID-19 pandemic restrictions on outcomes of HIV care among people living with HIV (PLHIV) aged ≥15 years in Kampala, Uganda. We designed a nonrandomized, quasi-experimental study using observational data retrieved from six large HIV clinics and used the data to construct two cohorts: a comparison cohort nonexposed to the restrictions and an exposed cohort that experienced the restrictions. The comparison cohort consisted of PLHIV commenced on anti-retroviral therapy (ART) between March 1, 2018, and February 28, 2019, followed for ≥1 year with outcomes assessed in March 2020, just before the restrictions were imposed. The exposed cohort comprised of PLHIV started on ART between March 1, 2019, and February 28, 2020, followed for ≥1 year with outcomes assessed in June 2021. The primary outcomes are retention, viral load testing, viral load suppression, and mortality. We employed inverse probability of treatment weighting using propensity score (IPTW-PS) to achieve comparability between the two cohorts on selected covariates. We estimated the effect of the restriction on the outcomes using logistic regression analysis weighted by propensity scores (PS), reported as odds ratio (OR) and 95% confidence interval (CI). We analyzed data for nine, 952 participants, with 5094 (51.2%) in the exposed group. The overall mean age was 32.7 ± 8.8 years. In the exposed group relative to the comparison group, viral load testing (OR, 1.68; 95% CI, 1.59-1.78) and viral load suppression (OR, 1.34; 95% CI, 1.110-1.63) increased while retention (OR, 0.76; 95% CI, 0.70-0.81) and mortality (OR, 0.75; 95% CI, 0.64-0.88) reduced. Among PLHIV in Kampala, Uganda, viral load testing and suppression improved while retention and mortality reduced during the COVID-19 pandemic restrictions due to new approaches to ART delivery and the scale-up of existing ART delivery models.

Recommendations for the use of propensity score methods in multiple sclerosis research

BACKGROUND

With many disease-modifying therapies currently approved for the management of multiple sclerosis, there is a growing need to evaluate the comparative effectiveness and safety of those therapies from real-world data sources. Propensity score methods have recently gained popularity in multiple sclerosis research to generate real-world evidence. Recent evidence suggests, however, that the conduct and reporting of propensity score analyses are often suboptimal in multiple sclerosis studies.

OBJECTIVES

To provide practical guidance to clinicians and researchers on the use of propensity score methods within the context of multiple sclerosis research.

METHODS

We summarize recommendations on the use of propensity score matching and weighting based on the current methodological literature, and provide examples of good practice.

RESULTS

Step-by-step recommendations are presented, starting with covariate selection and propensity score estimation, followed by guidance on the assessment of covariate balance and implementation of propensity score matching and weighting. Finally, we focus on treatment effect estimation and sensitivity analyses.

CONCLUSION

This comprehensive set of recommendations highlights key elements that require careful attention when using propensity score methods.

Acute pain consult and management is associated with improved mortality in rib fracture patients

INTRODUCTION

Traumatic rib fractures result in significant patient morbidity and mortality, which increases with patient age and number of rib fractures. A dedicated acute pain service (APS) providing expertize in multimodal pain management may reduce these risks and improve outcomes. We aimed to test the hypothesis that protocolized APS consultation decreases mortality and morbidity in traumatic rib fracture patients.

METHODS

This is a retrospective observational, propensity-matched cohort study of adult patients with trauma with rib fractures from 2012 to 2015, at a single, large level 1 trauma center corresponding to introduction and incorporation of APS consultation into the institutional rib fracture pathway. Using electronic medical records and trauma registry data, we identified adult patients presenting with traumatic rib fractures. Patients with hospital length of stay (LOS) ≥2 days were split into two cohorts based on presence of APS consult using 1:1 propensity matching of age, gender, comorbidities and injury severity. The primary outcome was difference in hospital mortality. Secondary outcomes included LOS and pulmonary morbidity.

RESULTS

2486 patients were identified, with a final matched cohort of 621 patients receiving APS consult and 621 control patients. The mortality rate was 1.8% among consult patients and 6.6% among control patients (adjusted OR 0.25, 95% CI 0.13 to 0.50; p=0.001). The average treatment effect of consult on mortality was 4.8% (95% CI 1.2% to 8.5%;. p<0.001). APS consultation was associated with increased intensive care unit (ICU) LOS (1.19 day; 95% CI 0.48 to 1.90; p=0.001) and hospital LOS (1.61 days; 95% CI 0.81 to 2.41 days; p<0.001). No difference in pulmonary complications was observed.

DISCUSSION

An APS consult in rib fracture patients is associated with decreased mortality and no difference in pulmonary complications yet increased ICU and hospital LOS.

Overall and patient-level comparative effectiveness of dimethyl fumarate and fingolimod: A precision medicine application to the Observatoire Français de la Sclérose en Plaques registry

Background

Comparing real-world effectiveness and tolerability of therapies for relapsing-remitting multiple sclerosis is increasingly important, though average treatment effects fail to capture possible treatment effect heterogeneity. With the clinical course of the disease being highly heterogeneous across patients, precision medicine methods enable treatment response heterogeneity investigations.

Objective

To compare real-world effectiveness and discontinuation profiles between dimethyl fumarate and fingolimod while investigating treatment effect heterogeneity with precision medicine methods.

Methods

Adults initiating dimethyl fumarate or fingolimod as a second-line therapy were selected from a French registry. The primary outcome was annualized relapse rate at 12 months. Seven secondary outcomes relative to discontinuation and disease progression were considered. A precision medicine framework was used to characterize treatment effect heterogeneity.

Results

Annualized relapse rates at 12 months were similar for dimethyl fumarate and fingolimod. The odd of treatment persistence was 47% lower for patients treated with dimethyl fumarate relative to those treated with fingolimod (odds ratio: 0.53, 95% confidence interval: 0.39, 0.70). None of the five precision medicine scoring approaches identified treatment heterogeneity.

Conclusion

These findings substantiated the similar effectiveness and different discontinuation profiles for dimethyl fumarate and fingolimod as a second-line therapy for relapsing-remitting multiple sclerosis, with no significant effect heterogeneity observed.

A tutorial comparing different covariate balancing methods with an application evaluating the causal effects of substance use treatment programs for adolescents

Randomized controlled trials are the gold standard for measuring causal effects. However, they are often not always feasible, and causal treatment effects must be estimated from observational data. Observational studies do not allow robust conclusions about causal relationships unless statistical techniques account for the imbalance of pretreatment confounders across groups and key assumptions hold. Propensity score and balance weighting (PSBW) are useful techniques that aim to reduce the observed imbalances between treatment groups by weighting the groups to look alike on the observed confounders. Notably, there are many methods available to estimate PSBW. However, it is unclear a priori which will achieve the best trade-off between covariate balance and effective sample size for a given application. Moreover, it is critical to assess the validity of key assumptions required for robust estimation of the needed treatment effects, including the overlap and no unmeasured confounding assumptions. We present a step-by-step guide to the use of PSBW for estimation of causal treatment effects that includes steps on how to evaluate overlap before the analysis, obtain estimates of PSBW using multiple methods and select the optimal one, check for covariate balance on multiple metrics, and assess sensitivity of findings (both the estimated treatment effect and statistical significance) to unobserved confounding. We illustrate the key steps using a case study examining the relative effectiveness of substance use treatment programs and provide a user-friendly Shiny application that can implement the proposed steps for any application with binary treatments.

Impact of conditional cash transfers on enrolment in community-based health insurance among female-headed households in south Gondar zone, Amhara region, Ethiopia

Ethiopia has been implementing its flagship social protection programme, Productive Safety Net Programme (PSNP), since 2005, mainly in drought prone and chronically food insecure woredas. In 2011, the country also launched Community-Based Health Insurance (CBHI). However, the two large-scale social protection programmes are not integrated well. This study examines the impact of participation in the conditional cash transfer (CCT) component of the PSNP (Public Works or PW) on enrolment in the CBHI among female-headed households in Amhara region. Data for the study generated through a cross-sectional survey collected from 365 PW-participating and non-participating female-headed households in south Gondar zone, Ebinat woreda (district). Inverse-probability-weighted regression adjustment (IPWRA) estimator is used to evaluate the impact of participating in PW component on CBHI enrolment decisions. Enrolment in CBHI among female-headed households is 63.6%. Data also show that 61.2% of insured and 27.1% of non-insured households receive CCTs. The study finds that participating in PSNP's CCT component increases the probability of CBHI enrolment among female-headed households by 16.3 percentage points. The finding informs efforts in integrating social protection programmes among most vulnerable households in rural Ethiopia. It also gives useful insights on the role of PSNP's CCT component to achieving universal health coverage through increasing insurance enrolment among most vulnerable households in Ethiopia.

Assessing long-term survival and hospitalization following transvenous lead extraction in patients with cardiac resynchronization therapy devices: A propensity score-matched analysis

Background

Longer-term outcomes of patients post transvenous lead extraction (TLE) are poorly understood in patients with cardiac resynchronization therapy (CRT) devices.

Objectives

A propensity score (PS)–matched analysis evaluating outcomes post TLE in CRT and non-CRT populations was performed.

Methods

Data from consecutive patients undergoing TLE between 2000 and 2019 were prospectively collected. Patients surviving to discharge and reimplanted with the same device were included. The cohort was split depending on presence of CRT device. Associations with all-cause mortality and hospitalization were assessed by Kaplan-Meier estimates. An exploratory endpoint was evaluated whether early (<7 days) or late (>7 days) reimplantation was associated with poorer outcomes.

Results

Of 1005 patients included, 285 (25%) had a CRT device. Median follow-up was 57.00 [27.00–93.00] months, age at explant was 67.7 ± 12.1 years, 83.3% were male, and 54.4% had an infective indication for TLE. PS was calculated using 43 baseline characteristics. After matching, 192 CRT patients were compared with 192 non-CRT patients. In the matched cohort, no significant difference with respect to mortality (hazard ratio [HR] = 1.01, 95% confidence interval [CI] [0.74–1.39], P = .093) or hospitalization risk (HR = 1.2, 95% CI [0.87–1.66], P = .265) was observed. In the matched CRT group, late reimplantation was associated with increased mortality (HR = 1.64, [1.04–2.57], P = .032) and hospitalization risk (HR = 1.57, 95% CI [1.00–2.46], P = .049].

Conclusion

Outcomes of CRT patients post TLE are similarly as poor as those of non-CRT patients in matched populations. Reimplantation within 7 days was associated with better outcomes in a CRT population but was not observed in a non-CRT population, suggesting prolonged periods without biventricular pacing should be avoided.

A multicenter propensity score matched analysis in 73,843 patients of an association of nutritional risk with mortality, length of stay and readmission rates

BACKGROUND

The reported prevalences and effects of nutritional risk vary widely in the literature because of both methodological differences (e.g., screening tools and statistical analyses) and different patient populations.

OBJECTIVE

In this study the authors analyzed in-hospital mortality, 30-d mortality, readmission within 4 mo, and justified length of stay (jLoS) (determined by governmental assessment to justify financial compensation) in hospitalized patients nutritionally at risk compared with hospitalized patients not at risk.

DESIGN

This was a multicenter retrospective cohort study in 6 Belgian hospitals among inpatients in 2018. Propensity score matching was applied, including comorbidity score and exact matching for hospital, age group, sex, type of admission, living situation, and medical specialty.

RESULTS

In total, 73,843 of 85,677 patients were screened at admission, with 16,141 found to have nutritional risk (prevalence of 21.9%). Oncology patients had the highest risk prevalence of 38.3%, whereas patients receiving plastic or reconstructive surgery had a prevalence of 5.2%. Patients nutritionally at risk had higher odds of dying in the hospital (5.1% compared with 3.3%; OR: 1.56; 95% CI: 1.37, 1.76), dying within 30 d of admission (6.8% compared with 4.3%; OR: 1.62; 95% CI: 1.45, 1.81) and being readmitted within 4 mo after discharge (35.5% compared with 32.9%; OR: 1.12; 95% CI: 1.07, 1.18). These differences were consistent across hospitals. The association between being nutritionally at risk and jLoS was ambiguous.

CONCLUSIONS

One out of 5 patients included in this study was nutritionally at risk. Using propensity score matching, higher odds of in-hospital mortality, readmission, and 30-d mortality were observed. In contrast to oft-reported increased length of stay with poor nutrition, propensity matched data for jLoS suggested that this association was less pronounced in this cohort.

Two healthy lifestyle scores are associated with lower subsequent fatigue risk using inverse probability weighting in an international longitudinal cohort of people with multiple sclerosis

BACKGROUND AND PURPOSE

Several modifiable lifestyle factors have been associated with the onset and health outcomes of multiple sclerosis (MS), including clinically significant fatigue. A combined lifestyle score approach represents one method of assessing their relationship with clinical outcomes. The aim was to examine the association of two lifestyle scores with clinically significant fatigue and change thereof over 2.5 years' follow-up using inverse probability treatment weighting (IPTW).

METHODS

Data on sociodemographic, lifestyle, and clinical characteristics surveyed from an international cohort of people with MS at baseline and at 2.5-year follow-up were used. Fatigue was defined by the Fatigue Severity Scale (FSS >5) and healthy lifestyle by the Healthy Lifestyle Index Score (HLIS) and the Smoking, Nutrition, Alcohol Consumption and Physical Activity (SNAP) score. Analyses were by IPTW accounting for age, sex, MS type, disability, treated comorbidity number, immunomodulatory medication use, prescription antifatigue medication use, and ongoing relapse symptoms.

RESULTS

In total, 1268 participants completed the FSS at both time points; approximately 62% had fatigue. Using doubly robust IPTW, high (>11/20) HLIS (odds ratio [OR] 0.90, 95% confidence interval [CI] 0.81-0.98) and high (>3/5) SNAP (OR 0.82, 95% CI 0.73-0.90) were each associated with lower risk of fatigue at follow-up. Evaluating change in fatigue, a higher SNAP score was associated with a lower risk of fatigue (OR 0.89, 95% CI 0.80-0.97) but the score for HLIS did not reach statistical significance (OR 0.93, 95% CI 0.85-1.01).

CONCLUSION

These results suggest a robust role for key lifestyle factors in preventing clinically significant fatigue and may represent a place for lifestyle modification in improving clinical outcomes in MS.

Intravenous Magnesium and Hospital Outcomes in Children Hospitalized With Asthma

BACKGROUND

Use of intravenous magnesium (IVMg) for childhood asthma exacerbations has increased significantly in the last decade. Emergency department administration of IVMg has been shown to reduce asthma hospitalization, yet most children receiving IVMg in the emergency department are subsequently hospitalized. Our objective with the study was to examine hospital outcomes of children given IVMg for asthma exacerbations.

METHODS

We conducted a retrospective cohort study using data from the Pediatric Health Information System. We used propensity score matching to compare children who received IVMg on the first day of hospitalization with those who did not. Primary outcomes were initiation and duration of noninvasive positive pressure ventilation. Secondary outcomes included mechanical ventilation (MV) initiation, duration of MV, length of stay, and subsequent tertiary medication use. Primary analysis was restricted to children admitted to nonintensive care inpatient units.

RESULTS

Overall, 91 309 hospitalizations met inclusion criteria. IVMg was administered in 25 882 (28.4%) children. After propensity score matching, IVMg was not significantly associated with lower initiation (adjusted odds ratio 0.88; 95% confidence interval [CI] 0.74-1.05) or shorter duration of noninvasive positive pressure ventilation (rate ratio 0.94; 95% CI 0.87-1.02). Similarly, no significant associations were seen for MV initiation, MV duration, or length of stay. IVMg was associated with lower subsequent tertiary medication use (adjusted odds ratio 0.66; 95% CI 0.60-0.72). However, the association was lost when ipratropium was removed from the tertiary medication definition.

CONCLUSIONS

IVMg administration was not significantly associated with improved hospital outcomes. Further study is needed to inform the optimal indications and timing of magnesium use during hospitalization.

Impact of Indonesia's national health insurance scheme on inequality in access to maternal health services: A propensity score matched analysis

Background

Reducing inequality in maternal, neonatal and infant mortality are key targets in the Sustainable Development Goals. This study is the first to evaluate the impact of Indonesia’s national health insurance scheme, Jaminan Kesehatan Nasional (JKN), on access to maternal health services by sociodemographic status.

Methods

Using data from the 2017 Indonesia Demographic and Health Survey (IDHS) on women with live births in 2016-2017, we conducted propensity score matching (PSM) analysis to evaluate the association of JKN enrollment on the following maternal health care utilisation outcomes: (1) at least four antenatal care (ANC4+) visits; (2) ANC4+ visits and received essential components of ANC; (3) skilled birth attendance; (4) facility-based delivery; (5) post-natal care (PNC); and (6) PNC with skilled provider. Analyses were conducted at the national level and by economic subgroup and region of residence. Additionally, we investigated the potential negative impact of JKN on access to maternal health services among the uninsured population by looking at trends over time using data from the 2012 and 2017 IDHS.

Results

Of the 5429 women who had recently given birth, 61% were insured by JKN in 2017. After matching treated and untreated women on key sociodemographic characteristics, enrollment in JKN was associated with a higher prevalence of receiving ANC4+ visits (7.4%, 95% confidence interval (CI) = 4.8-9.39); ANC4+ visits and received essential components of ANC (5.6%, 95% CI = 3.3-7.9); skilled birth attendance (3.0%, 95% CI = 1.5-4.5; facility-based delivery (10.2%, 95% CI = 7.5-12.7); PNC (4.0%, 95% CI = 2.2-5.7); PNC with skilled provider (4.5%, 95% CI = 2.6-6.5). Effect sizes were larger among the poor and those living in less-developed areas, such as Eastern Indonesia and Sulawesi, except for at least ANC4+ and received clinical components.

Conclusions

Expansion of health insurance coverage was associated with reductions in sociodemographic inequalities in access to maternal health services in Indonesia. However, large differences in utilisation persist across regions and by economic subgroup. Accelerating progress toward universal health coverage may reduce health inequalities in other low and middle-income countries.

Comparative Safety of Smoking Cessation Pharmacotherapies During a Government-Sponsored Reimbursement Program

INTRODUCTION

The British Columbia Ministry of Health launched a Smoking Cessation Program on September 30, 2011, providing financial coverage for smoking cessation pharmacotherapies. Although pharmacotherapies have been shown to have a moderate short-term benefit as a quitting aid, substantial cardiovascular and neuropsychiatric safety concerns have been identified in adverse-reporting databases, leading to prescription label warnings by Health Canada and the U.S. Food and Drug Administration. However, recent studies indicate these warnings may be without merit. This study examined the comparative safety of medications commonly used to aid smoking cessation.

AIMS AND METHODS

Population-based retrospective cohort study using B.C. administrative data to assess the relative safety between varenicline, bupropion, and nicotine replacement therapies (NRTs). The primary outcome was a composite of cardiovascular hospitalizations. Secondary outcomes included mortality, a composite of neuropsychiatric hospitalizations, and individual components of the primary outcome. Statistical analysis used propensity score-adjusted log-binomial regression models. A sensitivity analysis excluded patients with a history of cardiovascular disease.

RESULTS

The study included 116 442 participants. Compared with NRT, varenicline was associated with a 10% 1-year relative risk decrease of cardiovascular hospitalization (adjusted risk ratio [RR] = 0.90, 95% confidence interval (CI): 0.82 to 1.00), a 20% 1-year relative risk decrease of neuropsychiatric hospitalization (RR: 0.80, CI: 0.7 to 0.89), and a 19% 1-year relative risk decrease of mortality (RR: 0.81, CI: 0.71 to 0.93). We found no significant association between NRT and bupropion for cardiovascular hospitalizations, neuropsychiatric hospitalizations, or mortality.

CONCLUSIONS

Compared with NRT, varenicline is associated with fewer serious adverse events and bupropion the same number of serious adverse events.

IMPLICATIONS

This study addresses the need for comparative safety evidence in a real-world setting of varenicline and bupropion against an active comparator. Compared with NRT, varenicline was associated with a decreased risk of mortality, serious cardiovascular events, and neuropsychiatric events during the treatment, or shortly after the treatment, in the general population of adults seeking pharmacotherapy to aid smoking cessation. These results provide support for the removal of the varenicline boxed warning for neuropsychiatric events and add substantively to the cardiovascular safety findings of previous observational studies and randomized clinical trials.

A review of the use of propensity score diagnostics in papers published in high-ranking medical journals

Background

Propensity scores are widely used to deal with confounding bias in medical research. An incorrectly specified propensity score model may lead to residual confounding bias; therefore it is essential to use diagnostics to assess propensity scores in a propensity score analysis. The current use of propensity score diagnostics in the medical literature is unknown. The objectives of this study are to (1) assess the use of propensity score diagnostics in medical studies published in high-ranking journals, and (2) assess whether the use of propensity score diagnostics differs between studies (a) in different research areas and (b) using different propensity score methods.

Methods

A PubMed search identified studies published in high-impact journals between Jan 1st 2014 and Dec 31st 2016 using propensity scores to answer an applied medical question. From each study we extracted information regarding how propensity scores were assessed and which propensity score method was used. Research area was defined using the journal categories from the Journal Citations Report.

Results

A total of 894 papers were included in the review. Of these, 187 (20.9%) failed to report whether the propensity score had been assessed. Commonly reported diagnostics were p-values from hypothesis tests (36.6%) and the standardised mean difference (34.6%). Statistical tests provided marginally stronger evidence for a difference in diagnostic use between studies in different research areas (p = 0.033) than studies using different propensity score methods (p = 0.061).

Conclusions

The use of diagnostics in the propensity score medical literature is far from optimal, with different diagnostics preferred in different areas of medicine. The propensity score literature may improve with focused efforts to change practice in areas where suboptimal practice is most common.

Propensity score methods in real-world epidemiology: A practical guide for first-time users

Real-world epidemiology gives us the unique opportunity to observe large numbers of people, and the actions and events that characterize their encounters with healthcare providers. However, the heterogeneity and sheer diversity of the population and healthcare systems makes it impossible for researchers to compare "like with like" when attempting to draw causal inferences about interventions and outcomes. The critical issue in epidemiological datasets relates to high risk of bias due to confounders that stem from baseline differences between groups. Propensity score (PS) techniques are statistical approaches that have been used to tackle potential imbalance in the comparison groups. The PS is the estimated probability (based on measured baseline covariates) that the patient receives a particular intervention. Patients that share similar PS will most likely have the same distributions of underlying covariates included in the PS. Implementation of PS methods may achieve better balance of covariates, but there is no consensus on the best way of capturing all relevant confounders for incorporation into the PS model. Should covariates be selected by clinical or epidemiological experts, or would data-driven algorithms (machine learning) offer more efficient and reliable methods of estimating PS and controlling for confounding? The PS can be incorporated into the analysis in different ways, each with its own strengths and limitations, and researchers must choose the best fit for their study objectives. PS methods are particularly advantageous in situations where there are large numbers of measured covariates but relatively few outcome events captured in healthcare administrative databases.

Does e-cigarette experimentation increase the transition to daily smoking among young ever-smokers in France?

INTRODUCTION

According to multiple studies, e-cigarette use among adolescents is associated with subsequent smoking initiation. However, little is known about its effect on the transition from smoking initiation to daily smoking.

METHODS

Using retrospective data from a French national representative survey collected in 2017 (n = 39,115), we analyzed the role of ever using e-cigarettes on daily cigarette smoking status at 17 among ever smokers (n = 21,401). Risk-ratios (RR) were computed through modified Poisson regressions with an inverse probability of treatment weighting (IPTW) approach.

RESULTS

Among French adolescents aged 17, 16.8 % declared current e-cigarette use (1.9 % reported daily use) and 34.1 % cigarette smoking (25.1 % reported daily smoking). Among ever-smokers, adolescents who declared having ever used e-cigarettes were less likely than those who did not to transition to daily smoking at 17: RR = 0.62 95 %CI [0.60 - 0.64]. We found similar results for those who experimented with e-cigarettes before initiating smoking, RR = 0.76 95 %CI [0.66 - 0.89].

CONCLUSIONS

Our results found no evidence of an increased risk of transitioning to daily smoking at 17 among ever-smokers who also experimented with e-cigarettes. Further studies should investigate the longer-term role of vaping on future smoking habits with the use of causal inference methods.

Obesity and surgical complications of pancreaticoduodenectomy: An observation study utilizing ACS NSQIP

BACKGROUND

An estimated 38% of US adults are obese. Obesity is associated with socioeconomic disparities and increased rates of comorbidities, and is a known risk factor for development of pancreatic cancer. As a fourth leading cause of death in the United States, pancreatic cancer is commonly treated with a pancreatico-duodenectomy (PD), or Whipple procedure. Data regarding the effects of obesity on post-operative complication rate primarily comes from specialized centers, however the results are mixed. Our aim is to elucidate the effects that obesity has on outcomes after PD for pancreatic head cancer using a national prospectively maintained clinical database.

METHOD

The 2010-2015 American College of Surgeons National Surgical Quality Improvement Project (ACS NSQIP) Participant Use Files (PUF) were used as the data source. We identified cases in which PD was performed (CPT code 48150) in the setting of a postoperative diagnosis of pancreatic cancer (ICD9 code 157.0). We excluded cases that had emergency admissions, BMI ≤18.5 kg/m², intraoperative wound classification of III or IV, and disseminated cancer. Cases with missing BMI, preoperative albumin, operative time, LOS data were also excluded. Multiple imputation for missing sex, race, functional status, and ASA classification using chained equations was performed.¹⁶ Patients that had BMI ≥30 kg/m² were considered obese, and patients with BMI <30 kg/m² were used as control.

RESULTS

3484 patients underwent pancreaticoduodenectomy for pancreatic cancer. 860 patients were identified as obese. Propensity score analysis was performed matching age, sex, race, functional status, presence of dyspnea, diabetes, hypertension, acute renal failure, dialysis dependence, ascites, steroid use, bleeding disorders, history of chronic obstructive pulmonary disease (COPD), congestive heart failure (CHF), weight loss, American Society of Anesthesiologists (ASA) classification, and preoperative albumin levels. After matching, obese patients had higher risk of 30-day postoperative complications compared to control, including organ space wound infections (OR 1.38, 95% CI 1.07-1.79, p = 0.0128), returning to the operating room (OR 1.39, 95% CI 1.01-1.91, p = 0.0461), failure to extubate for greater than 48 h (OR 1.60, 95% CI 1.09-2.34, p = 0.0153), death (OR 1.68, 95% CI 1.01-2.78, p = 0.0453), septic shock (OR 2.22, 95% CI 1.46-3.38, p = 0.0002), pulmonary embolism (OR 2.42, 95% CI 1.07-5.45, p = 0.0332), renal insufficiency (OR 2.67, 95% CI 1.33-5.38, p = 0.0058). Sensitivity analysis yielded similar results with the exception of risk for return to the operating room, death, and pulmonary embolism, P > .05.

CONCLUSION

In this large observational study using a national clinical database, obese patients undergoing PD for head of pancreas cancer had increased risk of postoperative complications and mortality in comparison to controls.

Propensity Score Methods in Health Technology Assessment: Principles, Extended Applications, and Recent Advances

Randomized clinical trials (RCT) are accepted as the gold-standard approaches to measure effects of intervention or treatment on outcomes. They are also the designs of choice for health technology assessment (HTA). Randomization ensures comparability, in both measured and unmeasured pretreatment characteristics, of individuals assigned to treatment and control or comparator. However, even adequately powered RCTs are not always feasible for several reasons such as cost, time, practical and ethical constraints, and limited generalizability. RCTs rely on data collected on selected, homogeneous population under highly controlled conditions; hence, they provide evidence on efficacy of interventions rather than on effectiveness. Alternatively, observational studies can provide evidence on the relative effectiveness or safety of a health technology compared to one or more alternatives when provided under the setting of routine health care practice. In observational studies, however, treatment assignment is a non-random process based on an individual’s baseline characteristics; hence, treatment groups may not be comparable in their pretreatment characteristics. As a result, direct comparison of outcomes between treatment groups might lead to biased estimate of the treatment effect. Propensity score approaches have been used to achieve balance or comparability of treatment groups in terms of their measured pretreatment covariates thereby controlling for confounding bias in estimating treatment effects. Despite the popularity of propensity scores methods and recent important methodological advances, misunderstandings on their applications and limitations are all too common. In this article, we present a review of the propensity scores methods, extended applications, recent advances, and their strengths and limitations.

Tomato and lycopene consumption is inversely associated with total and cause-specific mortality: a population-based cohort study, on behalf of the International Lipid Expert Panel (ILEP)

No data exist on the associations of dietary tomato and lycopene consumption with total and cause-specific mortality. Using the National Health and Nutrition Examination Surveys 1999-2010, we evaluted the long-term impact of tomato and lycopene intake on total and cause-specific (CHD and cerebrovascular disease) mortality. We also assessed the changes in cardio-metabolic risk factors according to tomato and lycopene intake. Vital status to 31 December 2011 was ascertained. Cox proportional hazard regression models (followed by propensity score matching) were used to investigate the link between tomato and lycopene consumption total, CHD and cerebrovascular mortality. Among the 23 935 participants included (mean age = 47·6 years, 48·8 % men), 3403 deaths occurred during 76·4 months of follow-up. Tomato intake was inversely associated with total (risk ratio (RR) 0·86, 95 % CI 0·81, 0·92), CHD (RR 0·76, 95 % CI 0·70, 0·85) and cerebrovascular (RR 0·70, 95 % CI 0·62, 0·81) mortality. Similar inverse associations were found between lycopene consumption, total (RR 0·76, 95 % CI 0·72, 0·81), CHD (RR 0·73, 95 % CI 0·65, 0·83) and cerebrovascular (RR 0·71, 95 % CI 0·65, 0·78) mortality; these associations were independent of anthropometric, clinical and nutritional parameters. Age and obesity did not affect the association of tomato and lycopene consumption with total, CHD and cerebrovascular mortality. C-reactive protein significantly moderated the link between lycopene and tomato intake with total, CHD and cerebrovascular mortality. ANCOVA showed that participants with a higher tomato and lycopene consumption had a more cardio-protective profile compared with those with a lower intake. Our results highlighted the favourable effect of tomato and lycopene intake on total and cause-specific mortality as well as on cardio-metabolic risk factors. These findings should be taken into consideration for public health strategies.

Prostaglandins and cesarean delivery for nonreassuring fetal status in patients delivering small-for-gestational age neonates at term

Objective: Growth-restricted fetuses have been excluded from many randomized trials of prostaglandins for labor induction. As prostaglandins, particularly misoprostol, are associated with increased rates of cesarean delivery for nonreassuring fetal heart tracing, it is important to assess their safety in pregnancies at higher risk of this complication. The objective of this study was to estimate the association between use of prostaglandins for labor induction in term singleton pregnancies complicated by delivery of small-for-gestational age (SGA) neonates and the risk of cesarean delivery for nonreassuring fetal status (NRFS).Materials and methods: Retrospective cohort study of singleton deliveries ≥37 weeks following induction of labor in patients with SGA (birthweight <10% percentile for gestational age). Patients with prior cesarean delivery or neonates with major congenital anomalies were excluded. Patients were categorized by exposure to prostaglandins. The primary outcome was cesarean delivery for NRFS. Secondary outcomes were any cesarean delivery, a composite of a 5-min Apgar score <7, admission to the neonatal intensive care unit, or neonatal death, and a composite of maternal morbidity (transfusion, postpartum hemorrhage, wound infection, endometritis, fever). Propensity scores for exposure were estimated using a logistic regression model, including parity, comorbidities, and Bishop score. Stabilized weights from inverse probability of treatment weighting were used. Outcomes were compared with relative risks (RRs) and 95% confidence intervals (CIs).Results: There were 1097 patients: 587 (53.5%) exposed to prostaglandins and 510 (46.5%) unexposed. Covariates were balanced in the stabilized sample. Overall, 166 (15.1%) patients had cesarean deliveries for NRFS. In unadjusted analysis, prostaglandin use was associated with an increased RR of cesarean for NRFS (18.3 versus 11.0%, RR: 1.71, 95% CI: 1.27-2.30). In propensity-score-weighted analysis, the RR for cesarean for NRFS was 1.22 (95% CI: 0.93-1.59). There was no significant association between prostaglandin exposure and all-cause cesarean delivery, maternal morbidity, or neonatal morbidity.Conclusion: In propensity score analysis, there was no association between the use of prostaglandins for labor induction at term and cesarean for NRFS in pregnancies complicated by SGA. However, given the retrospective nature of the study, these results should be interpreted with caution.

Urinary pesticide concentrations in French adults with low and high organic food consumption: results from the general population-based NutriNet-Santé

An organic diet may reduce dietary exposure to pesticides but findings based on observational data are scant. We aimed to compare urinary pesticide concentrations between "organic" and "conventional" consumers from the NutriNet-Santé study. Organic food consumption was determined using a self-reported food frequency questionnaire. Individuals with a proportion of organic food in the whole diet (in g/d) below 10% were defined as low organic food consumers and those whose proportion was above 50% as high organic food consumers. A propensity score matching procedure was then used to obtain two similar subsets of 150 participants, differing mostly by the organic valence of their diet. Urinary pesticide and metabolite concentrations (organophosphorus, pyrethroid, and azole compounds) were determined by UPLC-MS/MS, standardized with respect to creatinine. The molar sums of total diethylphosphates, dimethylphosphates, and dialkylphosphates were also computed. Differences in distributions across groups were tested using Wilcoxon signed-rank test for matched data. Mean age was 58.5 years and 70% of participants were women. Significantly lower urinary levels of diethylthiophosphate, dimethylthiophosphate, dialkylphosphates, and free 3-phenoxybenzoic acid were observed among organic consumers compared to conventional consumers. Our findings confirm that exposure to certain organophosphate and pyrethroïd pesticides in adults may be lowered by switching from conventional to organic foods. This is particularly of high interest among conventional fruit and vegetable consumers, as their exposure may be the highest.

Some Differences in Nutritional Biomarkers are Detected Between Consumers and Nonconsumers of Organic Foods: Findings from the BioNutriNet Project

BACKGROUND

Meta-analyses have compared the nutrient content of both organic and nonorganic foods. However, the impacts of such variations on human nutritional biomarkers still need to be assessed.

OBJECTIVE

In a nested clinical study from the NutriNet-Santé study, we aimed to compare the nutritional status of "organic" and "nonorganic" food consumers matched on a propensity score.

METHODS

Based on self-reported organic food consumption assessed through a food frequency questionnaire (FFQ), 150 low and 150 high organic food consumers were selected with <10% or >50% of organic food in their diet, respectively (expressed as the proportion of organic food in the whole diet in g/d). Participants were matched using a propensity score derived from socio-demographic, food, and health variables. Fasting plasma samples were analyzed using acknowledged laboratory methods for measurements of iron status, magnesium, copper, cadmium, carotenoids, vitamins A and E, and fatty acids.

RESULTS

We found significant differences between low and high organic food consumers with similar dietary patterns, with respect to plasma concentrations of magnesium, fat-soluble micronutrients (α-carotene, β-carotene, lutein, and zeaxanthin), fatty acids (linoleic, palmitoleic, γ-linolenic, and docosapentanoeic acids), and some fatty acid desaturase indexes. No differences between the 2 groups were detected for plasma concentrations of iron, copper, cadmium, lycopene, β-cryptoxanthin, or vitamins A and E.

CONCLUSION

If confirmed by other studies, our data suggest that a high consumption of organic foods, compared with very low consumption, modulates to some extent, the nutritional status of individuals with similar dietary patterns. Further research including prospective cohort studies is needed to evaluate the clinical relevance of such differences.

Merits and caveats of propensity scores to adjust for confounding

Proper adjustment for confounding is essential when estimating the effects of treatments or risk factors on health outcomes in observational data. To this end, various statistical methods have been developed. In the past couple of years, the use of propensity scores (PSs) to control for confounding has increased. Proper understanding of this method is necessary to critically appraise research in which it is applied. In this article, we provide an overview of PS methods, explaining their concept, advantages and possible disadvantages. Furthermore, the use of PS matching, PS adjustment and PS weighting is illustrated using data from the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD) cohort of dialysis patients.

Predictors of acute pancreatitis with low elevation of serum amylase

Background and aims

Serum amylase is a traditional measure used to establish the diagnosis of acute pancreatitis (AP). The current study aimed to assess the predictors and clinical outcome of AP with low serum amylase.

Methods

All patients were divided into two groups, based on their serum amylase level within the first 2 days after hospital admission: group 1 (amylase ≥300 U/L) and group 2 (amylase <300 U/L). Clinical outcomes were compared between the two groups before and after 1:1 propensity score matching. Clinical and biochemical parameters were collected and evaluated as potential predictors of AP with low serum amylase.

Results

A total of 464 patients were enrolled. After propensity score matching according to age, gender, time interval before admission, hematocrit, blood urea nitrogen and creatinine, 108 matched pairs of patients were selected. There was no significant statistical difference between group 2 and group 1 with respect to severity of AP, median days of stay in hospital and death. Multivariate analysis indicated that biliary etiology (odds ratio [OR]: 0.499; 95% confidence interval [CI]: 0.265-0.942; P=0.003), low-density lipoprotein cholesterol (LDL-C) (OR: 1.009; 95% CI: 1.002-1.017; P=0.017) and triglyceride levels (OR: 1.001; 95% CI: 1.0001-1.001; P=0.015) were independently associated with development of AP along with low serum amylase.

Conclusion

Serum amylase level was not related to the severity of AP, median hospital stay (days) and death. Biliary etiology, LDL-C and triglyceride levels were independently associated with the development of AP with lower elevation of serum amylase.

Tips and tricks of the propensity score methods in the thoracic surgery research

Without randomization, the differences in the distribution of baseline covariates can confound the evaluation of outcomes between the groups. To estimate the causal effects of treatment on the results randomized clinical trials (RCT) are routinely used. When RCT are not feasible for cost, time, and ethical issues, the effect of treatment on an inevitable outcome could be investigated by using a non-experimental study design. The propensity score (PS) refers to the individual probability, for a subject involved in a study, of receiving a new treatment rather than the control treatment. PS matching is a valuable and increasingly popular tool for dealing with observational data and non-random treatment assignment. Nevertheless, surgeons need to proceed with caution and apply PS methods appropriately.

Prospective association between consumption frequency of organic food and body weight change, risk of overweight or obesity: results from the NutriNet-Santé Study

A lower BMI has been reported among consumers of organic foods, but this relationship has never been examined in a prospective design study. Our aim was to prospectively investigate the association between frequency of organic food consumption and weight change. We analysed data from 62 224 participants of the NutriNet-Santé cohort (78 % women, mean age=45 years) with information on consumption frequency of organic foods, dietary intake and repeated anthropometric data. For sixteen products, participants reported their consumption frequency of labelled organic foods (never, occasionally, most of the time). An organic score (OS) with a maximum of thirty-two points was computed. The associations of the OS (modeled as quartiles (Q)) with change in BMI during follow-up (on average 3·1 years) and with the risk of overweight and obesity were estimated by ANCOVA and multivariable logistic regression. A lower BMI increase was observed across quartiles of the OS (mean difference Q4 v. Q1=-0·16 (95 % CI -0·32, -0·01). An increase in the OS was associated with a lower risk of overweight and obesity (among non-overweight and non-obese participants at inclusion): OR for Q4 v. Q1 were 0·77 (95 % CI 0·68, 0·86) and 0·69 (95 % CI 0·58, 0·82), respectively. Concerning obesity risk, the association was stronger among participants with higher adherence to nutritional guidelines. This study supports a strong protective role of consumption frequency of organic foods with regard to the risk of overweight and obesity that depends on overall dietary quality. Upon confirmation, these results may contribute to fine-tune nutritional guidelines by accounting for farming practices in food production.