Differences in target estimands between different propensity score-based weights

PURPOSE

Propensity score weighting is a popular approach for estimating treatment effects using observational data. Different sets of propensity score-based weights have been proposed, including inverse probability of treatment weights whose target estimand is the average treatment effect, weights whose target estimand is the average treatment effect in the treated (ATT), and, more recently, matching weights, overlap weights, and entropy weights. These latter three sets of weights focus on estimating the effect of treatment in those subjects for whom there is clinical equipoise. We conducted a series of simulations to explore differences in the value of the target estimands for these five sets of weights when the difference in means is the measure of treatment effect.

METHODS

We considered 648 scenarios defined by different values of the prevalence of treatment, the c-statistic of the propensity score model, the correlation between the linear predictors for treatment selection and the outcome, and by the magnitude of the interaction between treatment status and the linear predictor for the outcome in the absence of treatment.

RESULTS

We found that, when the prevalence of treatment was low or high and the c-statistic of the propensity score model was moderate to high, that matching weights, overlap weights, and entropy weights had target estimands that differed meaningfully from the target estimand of the ATE weights.

CONCLUSIONS

Researchers using matching weights, overlap weights, and entropy weights should not assume that the estimated treatment effect is comparable to the ATE.

Effects of a mastitis J5 bacterin vaccination on the productive performance of dairy cows: An observational study using propensity score matching techniques

Inferring causal effects between variables when utilizing observational data is challenging due to confounding factors not controlled through a randomized experiment. Propensity score matching can decrease confounding in observational studies and offers insights about potential causal effects of prophylactic management interventions such as vaccinations. The objective of this study was to determine potential causality and impact of vaccination with an Escherichia coli J5 bacterin on the productive performance of dairy cows applying propensity score matching techniques to farm-recorded (e.g., observational) data. Traits of interest included 305-d milk yield (MY305), 305-d fat yield (FY305), 305-d protein yield (PY305), and somatic cell score (SCS). Records from 6,418 lactations generated by 5,121 animals were available for the analysis. Vaccination status of each animal was obtained from producer-recorded information. Confounding variables considered were herd-year-season groups (56 levels), parity (5 levels: 1, 2, 3, 4, and ≥5), and genetic quartile groups (4 levels: top 25% through bottom 25%) derived from genetic predictions for MY305, FY305, PY305, and SCS, as well as for the genetic susceptibility to mastitis. A logistic regression model was applied to estimate the propensity score (PS) for each cow. Subsequently, PS values were used to form pairs of animals (1 vaccinated with 1 unvaccinated control), depending on their PS similarities (difference in PS values of cows within a match required to be <20% of 1 standard deviation of the logit of PS). After the matching process, 2,091 pairs of animals (4,182 records) remained available to infer the causal effects of vaccinating dairy cows with the E. coli J5 bacterin. Causal effects estimation was performed using 2 approaches: simple matching and a bias-corrected matching. According to the PS methodology, causal effects of vaccinating dairy cows with a J5 bacterin on their productive performance were identified for MY305. The simple matched estimator suggested that vaccinated cows produced 163.89 kg more milk over an entire lactation when compared with nonvaccinated counterparts, whereas the bias-corrected estimator suggested that such increment in milk production was of 150.48 kg. Conversely, no causal effects of immunizing dairy cows with a J5 bacterin were identified for FY305, PY305, or SCS. In conclusion, the utilization of PS matching techniques applied to farm-recorded data was feasible and allowed us to identify that vaccination with an E. coli J5 bacterin relates to an overall milk production increment without compromising milk quality.

Efficact of Supplemental Oxygen During Procedural Sedation and Analgesia in Elderly Patients in the Emergency Department

BACKGROUND

The use of supplemental oxygen (SO) for procedural sedation and analgesia (PSA) is recommended in many guidelines, but the evidence of SO for the elderly is limited.

OBJECTIVES

This study aimed to compare the incidence of hypoxia with or without SO in PSA for the elderly patients.

METHODS

We prospectively collected data on all patients undergoing PSA in the emergency department (ED) from May 2017 through December 2021. These data are from the Japanese Procedural SedaTion and Analgesia Registry. We included all elderly patients (65 years and older) who received PSA in the ED. We performed propensity score analysis for inverse probability of treatment weighting (IPTW) to balance the baseline characteristics. The primary outcome was the incidence of hypoxia (SpO2 < 90%), and the secondary outcome was the incidence of bag-valve mask ventilation.

RESULTS

Among 1465 patients in the registry, we included 816 (55.7%) patients in the analysis. After propensity score method for IPTW, the distributions of confounders were closely balanced between the two groups. The incidence of hypoxia was significantly lower in the SO group compared with the non-SO group (6.2% vs. 19.3%; difference -13.1%; 95% confidence interval [CI] -9.8 to -16.4; p < 0.001). SO was also associated with a lower incidence of bag-valve mask ventilation (5.2% vs. 15.4%; difference -10.2%; 95% CI -7.1 to -13.2; p < 0.001).

CONCLUSIONS

In a propensity-matched analysis, SO was associated with a lower incidence of hypoxia in elderly patients during ED PSA.

Propensity score weighting methods for causal subgroup analysis with time-to-event outcomes

Evaluating causal effects of an intervention in pre-specified subgroups is a standard goal in comparative effectiveness research. Despite recent advancements in causal subgroup analysis, research on time-to-event outcomes has been lacking. This article investigates the propensity score weighting method for causal subgroup survival analysis. We introduce two causal estimands, the subgroup marginal hazard ratio and subgroup restricted average causal effect, and provide corresponding propensity score weighting estimators. We analytically established that the bias of subgroup-restricted average causal effect is determined by subgroup covariate balance. Using extensive simulations, we compare the performance of various combinations of propensity score models (logistic regression, random forests, least absolute shrinkage and selection operator, and generalized boosted models) and weighting schemes (inverse probability weighting, and overlap weighting) for estimating the causal estimands. We find that the logistic model with subgroup-covariate interactions selected by least absolute shrinkage and selection operator consistently outperforms other propensity score models. Also, overlap weighting generally outperforms inverse probability weighting in terms of balance, bias and variance, and the advantage is particularly pronounced in small subgroups and/or in the presence of poor overlap. We applied the methods to the observational Comparing Options for Management: PAtient-centered REsults for Uterine Fibroids study to evaluate the causal effects of myomectomy versus hysterectomy on the time to disease recurrence in a number of pre-specified subgroups of patients with uterine fibroids.

Covariate adjustment in randomized clinical trials with missing covariate and outcome data

When analyzing data from randomized clinical trials, covariate adjustment can be used to account for chance imbalance in baseline covariates and to increase precision of the treatment effect estimate. A practical barrier to covariate adjustment is the presence of missing data. In this article, in the light of recent theoretical advancement, we first review several covariate adjustment methods with incomplete covariate data. We investigate the implications of the missing data mechanism on estimating the average treatment effect in randomized clinical trials with continuous or binary outcomes. In parallel, we consider settings where the outcome data are fully observed or are missing at random; in the latter setting, we propose a full weighting approach that combines inverse probability weighting for adjusting missing outcomes and overlap weighting for covariate adjustment. We highlight the importance of including the interaction terms between the missingness indicators and covariates as predictors in the models. We conduct comprehensive simulation studies to examine the finite-sample performance of the proposed methods and compare with a range of common alternatives. We find that conducting the proposed adjustment methods generally improves the precision of treatment effect estimates regardless of the imputation methods when the adjusted covariate is associated with the outcome. We apply the methods to the Childhood Adenotonsillectomy Trial to assess the effect of adenotonsillectomy on neurocognitive functioning scores.

Evaluating the impact of sickle cell disease on COVID-19 susceptibility and severity: a retrospective cohort study based on electronic health record

Background

Sickle cell trait/disease (SCT/SCD) are enriched among Black people and associated with various comorbidities. The overrepresentation of these characteristics prevents traditional regression approach obtaining convincing evidence for the independent effect of SCT/SCD on other health outcomes. This study aims to investigate the association between SCT/SCD and COVID-19-related outcomes using causal inference approaches that balance the covariate.

Methods

We leveraged electronic health record (EHR) data from the University of Chicago Medicine between March 2020 and December 2021. Demographic characteristics were retrieved. Medical conditions were identified using ICD-10 codes. Five approaches, including two traditional regression approaches (unadjusted and adjusted) and three causal inference approaches [covariate balancing propensity score (CBPS) matching, CBPS weighting, and CBPS adjustment], were employed.

Results

A total of 112,334 patients were included in the study, among which 504 had SCT and 388 SCD. Patients with SCT/SCD were more likely to be non-Hispanic Black people, younger, female, non-smokers, and had a diagnosis of diabetes, heart failure, asthma, and cerebral infarction. Causal inference approaches achieved a balanced distribution of these covariates while traditional approaches failed. Across these approaches, SCD was consistently associated with COVID-19-related pneumonia (odds ratios (OR) estimates, 3.23 (95% CI: 2.13-4.89) to 2.57 (95% CI: 1.10-6.00)) and pain (OR estimates, 6.51 (95% CI: 4.68-9.06) to 2.47 (95% CI: 1.35-4.49)). While CBPS matching suggested an association between SCD and COVID-19-related acute respiratory distress syndrome (OR = 2.01, 95% CI: 0.97-4.17), this association was significant in other approaches (OR estimates, 2.96 (95% CI: 1.69-5.18) to 2.50 (95% CI: 1.43-4.37)). No association was observed between SCT and COVID-19-related outcomes in causal inference approaches.

Conclusion

Using causal inference approaches, we provide comprehensive evidence for the link between SCT/SCD and COVID-19-related outcomes.

Association between outpatient cardiac rehabilitation and all-cause mortality after cardiovascular surgery: A propensity score-matched analysis

Objectives

Cardiac rehabilitation (CR) is a class I recommendation in the treatment guidelines for cardiovascular disease; however, its postoperative prognostic effects after surgery are not fully understood. Therefore, this study aimed to examine the effect of multidisciplinary outpatient CR on postdischarge all-cause mortality in patients who underwent cardiovascular surgery.

Methods

This retrospective cohort study included consecutive patients who underwent elective cardiovascular surgery between April 2015 and March 2021. Patients were categorized into CR and non-CR groups. The primary outcome measure was all-cause mortality. Propensity score-matching analysis was performed to minimize selection bias and differences in clinical characteristics. The propensity score for each patient was produced using logistic regression analysis, with the CR group and the subsequent 27 variables as the dependent and independent variables, respectively.

Results

In our cohort (n = 1095), 51 patients (4.7%) died during the follow-up period (mean, 1042 days). The CR group had a significantly lower mortality rate than the non-CR group (hazard ratio, 0.45; 95% CI, 0.21-0.95; P = .036). After propensity score matching adjusted for confounders, the association between CR and reduced risk of all-cause mortality remained (hazard ratio, 0.35; 95% CI, 0.14-0.85; P = .02).

Conclusions

Postdischarge multidisciplinary outpatient CR in patients who underwent cardiovascular surgery was associated with a substantial survival benefit, which persisted after adjusting for variables, including age, operative factors, physical and cognitive functions, and nutritional status.

Variance estimation of the risk difference when using propensity-score matching and weighting with time-to-event outcomes

Observational studies are increasingly being used in medicine to estimate the effects of treatments or exposures on outcomes. To minimize the potential for confounding when estimating treatment effects, propensity score methods are frequently implemented. Often outcomes are the time to event. While it is common to report the treatment effect as a relative effect, such as the hazard ratio, reporting the effect using an absolute measure of effect is also important. One commonly used absolute measure of effect is the risk difference or difference in probability of the occurrence of an event within a specified duration of follow-up between a treatment and comparison group. We first describe methods for point and variance estimation of the risk difference when using weighting or matching based on the propensity score when outcomes are time-to-event. Next, we conducted Monte Carlo simulations to compare the relative performance of these methods with respect to bias of the point estimate, accuracy of variance estimates, and coverage of estimated confidence intervals. The results of the simulation generally support the use of weighting methods (untrimmed ATT weights and IPTW) or caliper matching when the prevalence of treatment is low for point estimation. For standard error estimation the simulation results support the use of weighted robust standard errors, bootstrap methods, or matching with a naïve standard error (i.e., Greenwood method). The methods considered in the article are illustrated using a real-world example in which we estimate the effect of discharge prescribing of statins on patients hospitalized for acute myocardial infarction.

Heterogeneous treatment effects of adjuvant therapy for patients with cervical cancer in the intermediate-risk group

BACKGROUND

The efficacy of adjuvant therapy for patients with cervical cancer with intermediate risk (CC-IR) remains controversial. We examined the impact of adjuvant therapy on survival outcomes in patients with CC-IR and evaluated the heterogeneous treatment effects (HTEs) of adjuvant therapies based on clinicopathologic characteristics.

METHODS

We retrospectively analyzed a previous Japanese nationwide cohort of 6192 patients with stage IB-IIB cervical cancer who underwent radical hysterectomy. We created two pairs of propensity score-matched treatment/control groups to investigate the treatment effects of adjuvant therapies: (1) adjuvant therapy versus non-adjuvant therapy; (2) chemotherapy versus radiotherapy conditional on adjuvant therapy. Multivariate analyses with treatment interactions were performed to evaluate the HTEs.

RESULTS

Among the 1613 patients with CC-IR, 619 and 994 were in the non-treatment and treatment groups, respectively. Survival outcomes did not differ between the two groups: 3-year progression-free survival (PFS) rates were 88.1% and 90.3% in the non-treatment and treatment groups, respectively (p = 0.199). Of the patients in the treatment group, 654 and 340 received radiotherapy and chemotherapy, respectively. Patients who received chemotherapy had better PFS than those who received radiotherapy (3-year PFS, 90.9% vs. 82.9%, p = 0.010). Tumor size was a significant factor that affected the treatment effects of chemotherapy; patients with large tumors gained better therapeutic effects from chemotherapy than those with small tumors.

CONCLUSION

Adjuvant therapy is optional for some patients with CC-IR; however, chemotherapy can be recommended as adjuvant therapy, particularly for patients with large tumors.

Adoption and Diffusion of Transcarotid Artery Revascularization in Contemporary Practice

BACKGROUND

In 2015, the FDA approved transcarotid artery revascularization (TCAR) as an alternative to carotid endarterectomy (CEA) and transfemoral carotid artery stenting (TF-CAS) for high-risk patients with carotid stenosis. This was granted in the absence of level 1 evidence to support TCAR. We aimed to document trends in TCAR utilization, its diffusion over time, and the clinical phenotypes of patients undergoing TCAR, CEA, and TF-CAS.

METHODS

We used the Vascular Quality Initiative to study patients who underwent TCAR. We calculated the number of TCARs performed and the percent of TCAR utilization versus CEA/TF-CAS. Using data from before TCAR was widespread, we calculated propensity scores for patients to receive CEA. We applied this model to patients undergoing carotid revascularization from 2016 to 2022 and grouped patients by the procedure they ultimately underwent, examining overlap in score distribution to measure patient similarity. We measured the trend of in-hospital stroke/death after TCAR.

RESULTS

We studied 31 447 patients who underwent TCAR from January 1, 2016 to March 31, 2022. The number of centers performing TCAR increased from 29 to 606. In 2021, TCAR represented 22.5% of carotid revascularizations at centers offering all 3 procedures. The percentage of patients that underwent TCAR who met approved high-risk criteria decreased from 88.5% to 80.9% (P<0.001). Those with a prior ipsilateral carotid procedure decreased from 20.6% in 2016 to 12.0% in 2021 (P<0.001). Patients undergoing TCAR after stroke increased from 19.7% to 30.7% (P<0.001). Propensity-score overlap was 55.4% for TCAR/CEA, and 58.6% for TCAR/TF-CAS, demonstrating that TCAR patients have a clinical phenotype mixed between those who undergo CEA and TF-CAS. The average in-hospital stroke/death risk after TCAR was 2.3% in 2016 and 1.7% in 2022 (P trend: 0.954).

CONCLUSIONS

TCAR now represents nearly 1-in-4 procedures at centers offering it. TCAR was increasingly performed among standard-risk patients and as a first-line procedural option after stroke. The absence of level 1 evidence underscores the importance of high-quality registry-based analyses to document TCAR's real-world outcomes and durability.

Adjusting for publication bias in meta-analysis via inverse probability weighting using clinical trial registries

Publication bias is a major concern in conducting systematic reviews and meta-analyses. Various sensitivity analysis or bias-correction methods have been developed based on selection models, and they have some advantages over the widely used trim-and-fill bias-correction method. However, likelihood methods based on selection models may have difficulty in obtaining precise estimates and reasonable confidence intervals, or require a rather complicated sensitivity analysis process. Herein, we develop a simple publication bias adjustment method by utilizing the information on conducted but still unpublished trials from clinical trial registries. We introduce an estimating equation for parameter estimation in the selection function by regarding the publication bias issue as a missing data problem under the missing not at random assumption. With the estimated selection function, we introduce the inverse probability weighting (IPW) method to estimate the overall mean across studies. Furthermore, the IPW versions of heterogeneity measures such as the between-study variance and the I2 measure are proposed. We propose methods to construct confidence intervals based on asymptotic normal approximation as well as on parametric bootstrap. Through numerical experiments, we observed that the estimators successfully eliminated bias, and the confidence intervals had empirical coverage probabilities close to the nominal level. On the other hand, the confidence interval based on asymptotic normal approximation is much wider in some scenarios than the bootstrap confidence interval. Therefore, the latter is recommended for practical use.

Comparisons of the Safety and Effectiveness of Robot-Assisted vs Laparoscopic Partial Nephrectomy for Central Renal Angiomyolipomas: A Propensity Score-Matched Analysis Study

Objective: To compare the safety and effectiveness of robot-assisted partial nephrectomy (RAPN) vs laparoscopic partial nephrectomy (LPN) in the treatment of central renal angiomyolipomas (AMLs). Methods: We retrospectively analyzed the clinical data of 103 patients who were treated with either RAPN or LPN for central AMLs between January 2017 and June 2022. Propensity scores were matched according to sex, age, laterality, body mass index, symptoms, diameter of tumor, location of tumor distribution, R.E.N.A.L score, preoperative hemoglobin, preoperative serum creatinine, preoperative estimated glomerular filtration rate, chronic disease, previous abdominal surgery, preoperative selective arterial embolization, American Society of Anesthesiologists scale, and duration of follow-up, and after matching, perioperative and prognostic data of the two groups were compared. Results: A total of 57 patients underwent RAPN, and 46 patients underwent LPN. Before matching, there were more complex AMLs in the RAPN group, and R.E.N.A.L scores differed between the two groups (10 vs 9, p < 0.001). After matching, the median warm ischemic time in the RAPN group was significantly shorter than that in the LPN group (21.5 minutes vs 28 minutes, p = 0.034), as well as the median time of postoperative mobilization (1 day vs 2 days, p < 0.001). The other indicators were not significantly different between the groups. Conclusions: For central AMLs, both RAPN and LPN were safe and feasible surgical treatments, but RAPN might be associated with shorter warm ischemia time and earlier postoperative mobilization.

Medical Management Versus Endovascular Treatment for Large-Vessel Occlusion Anterior Circulation Stroke With Low NIHSS

BACKGROUND

Endovascular treatment (EVT) for acute ischemic stroke (AIS) patients presenting with National Institutes of Health Stroke Scale score of 0 to 5 is common in clinical practice but has not yet been proven safe and effective. Our objective is to assess whether EVT on top of best medical treatment (BMT) in AIS patients with large-vessel occlusion of the anterior circulation presenting with mild symptoms is beneficial compared with BMT.

METHODS

We searched MEDLINE, SCOPUS, and reference lists of retrieved articles published until December 28, 2022. A systematic literature search was conducted to identify clinical trials or observational cohort studies evaluating patients with AIS due to anterior circulation large-vessel occlusion and admission National Institutes of Health Stroke Scale score ≤5 treated with EVT versus BMT alone. The primary outcome was excellent functional outcome (modified Rankin Scale score 0-1) at 3 months. The protocol had been registered before data collection (PROSPERO).

RESULTS

Eleven observational eligible studies were included in the meta-analysis, comprising a total of 2019 AIS patients with National Institutes of Health Stroke Scale score ≤5 treated with EVT versus 3171 patients treated with BMT. EVT was not associated with excellent functional outcome (risk ratio, 1.10 [95% CI, 0.93-1.31]). When stratified for different study design (per-protocol versus intention-to-treat), there were no significant subgroup differences. EVT was not associated with good functional outcome (modified Rankin Scale score 0-2; risk ratio, 1.01 [95% CI, 0.89-1.16]) or reduced disability at 3 months (common odds ratio, 0.92 [95% CI, 0.60-1.41]). Symptomatic intracranial hemorrhage was more common in the patients receiving EVT (risk ratio, 3.53 [95% CI, 2.35-5.31]). No correlation was found between EVT and mortality at 3 months (risk ratio, 1.34 [95% CI, 0.83-2.18]). The same overall associations were confirmed in the sensitivity analysis of studies that performed propensity score matching.

CONCLUSIONS

EVT appears equivalent to BMT for patients with anterior circulation large-vessel occlusion AIS with low baseline National Institutes of Health Stroke Scale, despite the increased risk for symptomatic intracranial hemorrhage.

REGISTRATION

URL: https://www.crd.york.ac.uk/PROSPERO/; Unique identifier: CRD42022334417.

Propensity-based standardization to enhance the validation and interpretation of prediction model discrimination for a target population

External validation of the discriminative ability of prediction models is of key importance. However, the interpretation of such evaluations is challenging, as the ability to discriminate depends on both the sample characteristics (ie, case-mix) and the generalizability of predictor coefficients, but most discrimination indices do not provide any insight into their respective contributions. To disentangle differences in discriminative ability across external validation samples due to a lack of model generalizability from differences in sample characteristics, we propose propensity-weighted measures of discrimination. These weighted metrics, which are derived from propensity scores for sample membership, are standardized for case-mix differences between the model development and validation samples, allowing for a fair comparison of discriminative ability in terms of model characteristics in a target population of interest. We illustrate our methods with the validation of eight prediction models for deep vein thrombosis in 12 external validation data sets and assess our methods in a simulation study. In the illustrative example, propensity score standardization reduced between-study heterogeneity of discrimination, indicating that between-study variability was partially attributable to case-mix. The simulation study showed that only flexible propensity-score methods (allowing for non-linear effects) produced unbiased estimates of model discrimination in the target population, and only when the positivity assumption was met. Propensity score-based standardization may facilitate the interpretation of (heterogeneity in) discriminative ability of a prediction model as observed across multiple studies, and may guide model updating strategies for a particular target population. Careful propensity score modeling with attention for non-linear relations is recommended.

Comparison of complications after closure of totally implantable venous access devices with non-absorbable suture and n-butyl-2-cyanoacrylate (NBCA) skin adhesive: Propensity score matching analysis

PURPOSE

This study aimed to compare the complication rates of non-absorbable suture (NAS) and n-butyl-2-cyanoacrylate (NBCA) skin adhesive for skin closure during totally implantable venous access devices (TIVADs) implantation.

METHODS

Between March 2020 and February 2021, 586 consecutive patients who underwent TIVAD implantation were retrospectively analyzed. Two groups of patients suture with NAS (n = 299) or NBCA (n = 287) were followed up for 18 months to compare the occurrence of infection, thrombosis, and non-thrombotic malfunction. A total of 364 cases were extracted using propensity score matching in a 1:1 ratio. Mean TIVADs maintenance days were analyzed using Kaplan-Meier survival analysis.

RESULTS

Nineteen cases of complications occurred (0.294/1000 catheter-days) in the NAS group and 17 cases (0.210/1000 catheter-days) in the NBCA group. The difference in the complication rates between the two groups was not statistically significant (p = 0.725) after propensity score matching. Mean TIVADs maintenance days were 627.3 days in NAS group and 697.6 days in NBCA group. There was no statistically significant difference in the number of TIVADs maintenance days between the two groups (p = 0.081).

CONCLUSION

In TIVADs implantation, skin closure using NBCA showed no difference in the occurrence of infectious complications compared with conventional non-absorbable skin suture.

The Association Between Absolute Lymphocyte Count and Long-Term Mortality in Critically Ill Medical Patients: Propensity Score-Based Analyses

Objective

Absolute lymphocyte count (ALC) has been implicated with short-term outcomes in a number of diseases, and we aimed to investigate the association between week-one ALC and long-term mortality in patients who were admitted to the medical intensive care units (ICUs).

Methods

We enrolled patients who were admitted to the medical ICUs at the Taichung Veterans General Hospital, a referral centre located in central Taiwan, between 2015 and 2020 to conduct this retrospective cohort study. The outcome of interest was long-term all-cause mortality, and hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated to determine the association. Furthermore, we employed propensity score-matching (PSM) and weighting techniques, consisting of inverse probability of treatment weighting (IPTW) and covariate balancing propensity score (CBPS), to confirm the association between ALC and mortality.

Results

A total of 5722 critically ill patients were enrolled, and the one-year mortality was 44.8%. The non-survivor group had a lower ALC (1549, 1027-2388 vs 1948, 1373-2743 counts/μL, p<0.01) compared with those in the survivor group. Cox regression showed that low ALC was independently associated with mortality (adjHR 1.091, 95% CI 1.050-1.134). Propensity score-based analyses demonstrated the robust association, with adjHRs in the original, PSM, IPTW, and CBPS populations of 1.327 (95% CI 1.224-1.438), 1.301 (95% CI 1.188-1.424), 1.292 (95% CI 1.186-1.407), and 1.297 (95% CI 1.191-1.412), respectively. Sensitivity analyses further showed that the association between low ALC and mortality existed in a dose-response manner.

Conclusion

We found that low ALC was associated with long-term mortality in critically ill patients; further studies are warranted to validate and translate these findings into clinical utility.

Efficacy of Empirical Radioiodine Therapy in Patients with Differentiated Thyroid Cancer and Elevated Serum Thyroglobulin without Evidence of Structural Disease: A Propensity Score Analysis

We assessed the outcome of administration of empiric radioactive iodine (RAI) therapy to patients with differentiated thyroid cancer (DTC), in a propensity-score-matched cohort of patients with biochemical incomplete response (BIR) and without evidence of structural disease. We retrospectively evaluated 820 DTC patients without distant metastases, who underwent total thyroidectomy followed by RAI therapy, with available BIR at 12 months and follow-up evaluations. The patients were categorized according to the administration of empiric therapy (ET). To account for differences between patients with (n = 119) and without (n = 701) ET, a propensity-score-matched cohort of 119 ET and 119 no-ET patients was created. The need for additional therapy and the occurrence of structural disease were considered as end-points. During a median follow-up of 53 months (range 3-285), 57 events occurred (24% cumulative event rate). The rate of events was significantly higher in the no-ET compared to the ET patients (30% vs. 18% p < 0.001). The multivariate Cox analysis identified age (p < 0.01), pre-therapy Tg (p < 0.05) and empiric RAI therapy (p < 0.01) as predictors of outcome. The Kaplan-Meier analysis found that progression-free survival was lower in no-ET patients compared to the ET group (p < 0.01). In patients with DTC treated with surgery and RAI, and with biochemical incomplete response at the 12-month evaluation, their prognosis seemed to be affected by Tg values and the empiric treatment. The identification of candidates for this approach may improve prognosis.

SARS-CoV-2 Vaccination Response in Japanese Patients with Autoimmune Hepatitis: Results of Propensity Score-Matched Case-Control Study

BACKGROUND/AIMS

Although the World Health Organization declared the end of the public health emergency of international concern focusing on COVID-19 in May 2023, this bothersome virus continues to mutate, and the possibility of the emergence of mutant strains with high infectivity and severe disease rates has not disappeared. Thus, medical evidence must be accumulated, which is indispensable for protecting both patients under immunosuppressive treatments and the healthy population. This study examined SARS-CoV-2 vaccination responses in Japanese patients with autoimmune hepatitis (AIH) compared with healthy controls.

METHODS

This observational study registered 22 patients with histologically diagnosed AIH and 809 healthy controls in our hospital. Their Elecsys anti-SARS-CoV-2 spike antibody concentrations before and after vaccination were evaluated.

RESULTS

In this study, 72.7% and 18.2% of patients with AIH received steroids and azathioprine, respectively. Significant negative correlations were found between age and anti-SARS-CoV-2 spike antibody concentration in both groups; however, no sex differences were found. Although anti-SARS-CoV-2 spike antibody concentration was drastically augmented after the second vaccination (p < 0.05) in the AIH group, these levels were significantly lower than those in the controls (p < 0.05). In the age- and sex-matched analysis, the population ratio with a minimum response (≤100 binding antibody units (BAU/mL) was higher among patients with AIH than among controls 26 weeks after the second vaccination (44% vs. 7%, p < 0.05).

CONCLUSIONS

The anti-SARS-CoV-2 spike antibody concentration in AIH patients was significantly lower than that in controls after the second vaccination. Continued and widespread vaccination, particularly for patients requiring medical immunomodulation, is recommended.

Causal Responsibility Division of Chronological Continuous Treatment Based on Change-Point Detection

This paper introduces a novel approach, called causal relation quantification, based on change-point detection to address the issue of harmonic responsibility division in power systems. The proposed method focuses on determining the causal effect of chronological continuous treatment, enabling the identification of crucial treatment intervals. Within each interval, three propensity-score-based algorithms are executed to assess their respective causal effects. By integrating the results from each interval, the overall causal effect of a chronological continuous treatment variable can be calculated. This calculated overall causal effect represents the causal responsibility of each harmonic customer. The effectiveness of the proposed method is evaluated through a simulation study and demonstrated in an empirical harmonic application. The results of the simulation study indicate that our method provides accurate and robust estimates, while the calculated results in the harmonic application align closely with the real-world scenario as verified by on-site investigations.

Real-World Outcomes for Basilar Artery Occlusion Thrombectomy With Mild Deficits: The National Inpatient Sample

BACKGROUND

Thrombectomy for basilar artery occlusion (BAO) has proven efficacy in patients with moderate-to-severe deficits, but has unclear benefits for those with mild symptoms.

METHODS

Using an observational cohort design, the US National Inpatient Sample (2018-2020) was queried for adult patients with basilar artery occlusion and National Institutes of Health Stroke Scale (NIHSS) <10 for patients treated with thrombectomy versus medical management. The primary outcome of routine discharge (to home or self-care) was evaluated using multivariable logistic regression and propensity score matching, adjusted for baseline characteristics, stroke severity, and treatment with thrombolysis.

RESULTS

Of 17 019 with basilar artery occlusion, 5795 patients met the criteria for inclusion criteria for our study, and 880 (15.4%) were treated with endovascular thrombectomy. In the propensity score-matched cohort, 880 patients were treated with medical management and endovascular thrombectomy, respectively. In multivariable regression, endovascular thrombectomy was associated with both an increased odds of routine discharge (odds ratio, 1.95 [95% CI, 1.31-2.90]; P=0.001) and a decreased length of hospital stay (B, -0.74 [95% CI, -1.36 to -0.11]; P=0.02) compared with medical management. In the propensity score matched cohort, endovascular thrombectomy remained associated with greater odds of routine discharge (2.01 [95% CI, 1.21-3.34]; P=0.007) but no difference in length of hospital stay (B, -0.22 [95% CI, -0.90 to 0.46]; P=0.53).

CONCLUSIONS

Routine discharge was more common in this representative US cohort of patients with basilar artery occlusion and National Institutes of Health Stroke Scale <10 who underwent thrombectomy compared to conventional medical management. These findings suggest thrombectomy may be associated with better functional outcomes despite lower National Institutes of Health Stroke Scale and should be validated in a clinical trial setting.

Corticosteroid Therapy for Patients With Severe Fever With Thrombocytopenia Syndrome: A Nationwide Propensity Score-Matched Study in Japan

Background

Severe fever with thrombocytopenia syndrome (SFTS) is a life-threatening infectious disease for which no effective treatment strategy has been established. Although corticosteroids (CSs) are widely administered to patients with SFTS, their efficacy remains uncertain. This study aimed to assess the impact of CS therapy on the in-hospital mortality of patients with SFTS.

Methods

In this nationwide observational study using the Japanese Diagnosis Procedure Combination database, patients hospitalized for SFTS from April 2013 to March 2021 were reviewed. We compared patients who were treated with CSs to those who were treated without them after propensity score matching to adjust for their background, disease severity, and combination therapy.

Results

We included 494 patients with SFTS, and 144 pairs of them were analyzed after propensity score matching. No significant difference in the 30-day mortality (19% vs 15%, P = .272) and the number of survival days (log-rank test, P = .392) was found between the CS treatment group and the non-CS treatment group. However, in subgroup analyses, the CS treatment group tended to have better survival among patients with impaired consciousness on admission and/or shock status within 7 days after admission.

Conclusions

CS therapy does not seem effective for all patients with SFTS; however, the impact might be altered by disease severity assessed by the consciousness level and shock status. A large-scale interventional study is required to determine its efficacy, especially for critically ill patients with SFTS.

Nomogram for predicting survival of patients with gastric cancer and multiple primary malignancies: a real-world retrospective analysis using the Surveillance, Epidemiology and End Results database

OBJECTIVES

Gastric cancer combined with multiple primary malignancies (GCM) is increasingly common. This study investigated GCM clinical features and survival time.

METHODS

Patients with GCM and GC only (GCO) were selected from the Surveillance, Epidemiology and End Results (SEER) database. Survival was compared between GCM and GCO groups using propensity score matching. Then, the GCM group was divided into a training cohort and a validation cohort. These cohorts were used to establish a nomogram for survival prediction in patients with GCM.

RESULTS

Survival time was significantly longer in the GCM group than in the GCO group. All-subsets regression was used to identify four variables for nomogram establishment: age, gastric cancer sequence, N stage, and surgery. The concordance index and time-dependent receiver operating characteristic curve indicated that the nomogram had favorable discriminative ability. Calibration plots of predicted and actual probabilities showed good consistency in both the training and validation cohorts. Decision curve analysis and risk stratification showed that the nomogram was clinically useful; it had favorable discriminative ability to recognize patients with different levels of risk.

CONCLUSIONS

Compared with GCO, GCM is a relatively indolent malignancy. The nomogram developed in this study can help clinicians to assess GCM prognosis.

Racial and ethnic differences in neuropsychiatric symptoms and progression to incident cognitive impairment among community-dwelling participants

INTRODUCTION

Neuropsychiatric symptoms (NPS) are a risk factor for dementia; however, their prevalence and severity among ethnoracial groups are poorly understood.

METHODS

We used data from the National Alzheimer's Coordinating Center (NACC) (n = 6958; ≥50 years old). Cognitively normal participants at baseline, without any NPS or dementia diagnosis, had at least one follow-up. Survival analyses assessed the hazard ratio for 12 NPS models and progression to cognitive impairment. Propensity score weighting (PSW) matched participants on age, sex, education, and race/ethnicity.

RESULTS

All 12 NPS were significantly associated with progression to cognitive impairment. In the PSW models, compared to whites, Black/African Americans were more likely to progress to cognitive impairment across all 12 NPS models, followed by Hispanic, and then Asian participants.

DISCUSSION

PSW minimized selection bias to provide robust risk estimates. There is a higher risk of progressing to cognitive impairment for ethnoracial groups with NPS. Tailored screening of NPS and cognitive impairment should incorporate patient and caregiver reports.

Dronedarone Versus Sotalol in Antiarrhythmic Drug-Naive Veterans With Atrial Fibrillation

BACKGROUND

Sotalol and dronedarone are both used for maintenance of sinus rhythm for patients with atrial fibrillation. However, while sotalol requires initial monitoring for QT prolongation and proarrhythmia, dronedarone does not. These treatments can be used in comparable patients, but their safety and effectiveness have not been compared head to head. Therefore, we retrospectively evaluated the effectiveness and safety using data from a large health care system.

METHODS

Using Veterans Health Administration data, we identified 11 296 antiarrhythmic drug-naive patients with atrial fibrillation prescribed dronedarone or sotalol in 2012 or later. We excluded patients with prior conduction disease, pacemakers or implantable cardioverter-defibrillators, ventricular arrhythmia, cancer, renal failure, liver disease, or heart failure. We used natural language processing to identify and compare baseline left ventricular ejection fraction between treatment arms. We used 1:1 propensity score matching, based on patient demographics, comorbidities, and medications, and Cox regression to compare strategies. To evaluate residual confounding, we performed falsification analysis with nonplausible outcomes.

RESULTS

The matched cohort comprised 6212 patients (3106 dronedarone and 3106 sotalol; mean [±SD] age, 71±10 years; 2.5% female; mean [±SD] CHA2DS2-VASC, 2±1.3). The mean (±SD) left ventricular ejection fraction was 55±11 and 58±10 for dronedarone and sotalol users, correspondingly. Dronedarone, compared with sotalol, did not demonstrate a significant association with risk of cardiovascular hospitalization (hazard ratio, 1.03 [95% CI, 0.88-1.21]) or all-cause mortality (hazard ratio, 0.89 [95% CI, 0.68-1.16]). However, dronedarone was associated with significantly lower risk of ventricular proarrhythmic events (hazard ratio, 0.53 [95% CI, 0.38-0.74]) and symptomatic bradycardia (hazard ratio, 0.56 [95% CI, 0.37-0.87]). The primary findings were stable across sensitivity analyses. Falsification analyses were not significant.

CONCLUSIONS

Dronedarone, compared with sotalol, was associated with a lower risk of ventricular proarrhythmic events and conduction disorders while having no difference in risk of incident cardiovascular hospitalization and mortality. These observational data provide the basis for prospective efficacy and safety trials.

A review of the use of propensity score methods with multiple treatment groups in the general internal medicine literature

BACKGROUND

Propensity score (PS) methods with two treatment groups (e.g., treated vs. control) is a well-established technique for reducing the effects of confounding in nonrandomized studies. However, researchers are often interested in comparing multiple interventions. PS methods have been modified to incorporate multiple exposures. We described available techniques for PS methods in multicategory exposures (≥3 groups) and examined their use in the medical literature.

METHODS

A comprehensive search was conducted for studies published in PubMed, Embase, Google Scholar, and Web of Science until February 27, 2023. We included studies using PS methods for multiple groups in general internal medicine research.

RESULTS

The literature search yielded 4088 studies (2616 from PubMed, 86 from Embase, 85 from Google Scholar, 1671 from Web of Science, five from other sources). In total, 264 studies using PS method for multiple groups were identified; 61 studies were on general internal medicine topics and included. The most commonly used method was that of McCaffrey et al., which was used in 26 studies (43%), where the Toolkit for Weighting and Analysis of Nonequivalent Groups (TWANG) method and corresponding inverse probabilities of treatment weights were estimated via generalized boosted models. The next most commonly used method was pairwise propensity-matched comparisons, which was used in 20 studies (33%). The method by Imbens et al. using a generalized propensity score was implemented in six studies (10%). Four studies (7%) used a conditional probability of being in a particular group given a set of observed baseline covariates where a multiple propensity score was estimated using a non-parsimonious multinomial logistic regression model. Four studies (7%) used a technique that estimates generalized propensity scores and then creates 1:1:1 matched sets, and one study (2%) used the matching weight method.

CONCLUSIONS

Many propensity score methods for multiple groups have been adopted in the literature. The TWANG method is the most commonly used method in the general medical literature.