Research and scholarly methods: Propensity scores

Assessing Covariate Balance with Small Sample Sizes

Propensity score adjustment addresses confounding by balancing covariates in subject treatment groups through matching, stratification, or weighting. Diagnostics test the success of adjustment. For example, if the standardized mean difference (SMD) for a relevant covariate exceeds a threshold like 0.1, the covariate is considered imbalanced and the study may be invalid. Unfortunately, for studies with small or moderate numbers of subjects, the probability of falsely rejecting the validity of a study because of chance imbalance-the probability of asserting imbalance by using a cutoff for SMD when no underlying imbalance exists-can be grossly larger than a given nominal level like 0.05. In this paper, we illustrate that chance imbalance is operative in real-world settings even for moderate sample sizes of 2000. We identify a previously unrecognized challenge that as meta-analyses increase the precision of an effect estimate, the diagnostics must also undergo meta-analysis for a corresponding increase in precision. We propose an alternative diagnostic that checks whether the standardized mean difference statistically significantly exceeds the threshold. Through simulation and real-world data, we find that this diagnostic achieves a better trade-off of type 1 error rate and power than standard nominal threshold tests and not testing for sample sizes from 250 to 4000 and for 20 to 100,000 covariates. We confirm that in network studies, meta-analysis of effect estimates must be accompanied by meta-analysis of the diagnostics or else systematic confounding may overwhelm the estimated effect. Our procedure supports the review of large numbers of covariates, enabling more rigorous diagnostics.

Genomic variations associated with risk and protection against vincristine-induced peripheral neuropathy in pediatric cancer patients

Vincristine-induced peripheral neuropathy is a common and highly debilitating toxicity from vincristine treatment that affects quality of life and often requires dose reduction, potentially affecting survival. Although previous studies demonstrated genetic factors are associated with vincristine neuropathy risk, the clinical relevance of most identified variants is limited by small sample sizes and unclear clinical phenotypes. A genome-wide association study was conducted in 1100 cases and controls matched by vincristine dose and genetic ancestry, uncovering a statistically significant (p < 5.0 × 10-8) variant in MCM3AP gene that substantially increases the risk of neuropathy and 12 variants protective against neuropathy within/near SPDYA, METTL8, PDE4D, FBN2, ZFAND3, NFIB, PAPPA, LRRTM3, NRG3, VTI1A, ARHGAP5, and ACTN1. A follow-up pathway analysis reveals the involvement of four key pathways, including nerve structure and development, myelination, neuronal transmission, and cytoskeleton/microfibril function pathways. These findings present potential actionable genomic markers of vincristine neuropathy and offer opportunities for tailored interventions to improve vincristine safety in children with cancer. This study is registered with ClinicalTrials.gov under the title National Active Surveillance Network and Pharmacogenomics of Adverse Drug Reactions in Children (ID NCT00414115, registered on December 21, 2006).

Addiction Consult Service and Inpatient Outcomes Among Patients with OUD

BACKGROUND

Despite rising hospitalizations for opioid use disorder (OUD), rates of inpatient medications for OUD (MOUD) initiation are low. Addiction consult services (ACSs) facilitate inpatient MOUD initiation and linkage to post-discharge MOUD, but few studies have rigorously examined ACS OUD outcomes.

OBJECTIVE

To determine the association between ACS consultation and inpatient MOUD initiation, discharge MOUD provision, and post-discharge MOUD linkage.

DESIGN

Retrospective study comparing admissions that received an ACS consult and propensity score-matched historical control admissions.

SUBJECTS

One hundred admissions with an OUD-related diagnosis, of patients not currently receiving MOUD who received an ACS consult, and 100 matched historical controls.

INTERVENTION

Consultation from an interprofessional ACS offering expertise in MOUD initiation and linkage to post-discharge MOUD.

MAIN MEASURES

The primary outcome was inpatient MOUD initiation (methadone or buprenorphine). Secondary outcomes were inpatient buprenorphine initiation, inpatient methadone initiation, discharge prescription for buprenorphine, linkage to post-discharge MOUD (buprenorphine prescription within 60 days and new methadone administration at a methadone program within 30 days after discharge), patient-directed discharge, 30-day readmission, and 30-day emergency department (ED) visit.

KEY RESULTS

Among 200 admissions with an OUD-related diagnosis, those that received an ACS consultation were significantly more likely to have inpatient MOUD initiation (OR 2.57 [CI 1.44-4.61]), inpatient buprenorphine initiation (OR 5.50 [2.14-14.15]), a discharge prescription for buprenorphine (OR 17.22 [3.94-75.13]), a buprenorphine prescription within 60 days (22.0% vs. 0.0%, p < 0.001; of those with inpatient buprenorphine initiation: 84.6% vs. 0.0%), and new methadone administration at a methadone program within 30 days after discharge (7.0% vs. 0.0%, p = 0.007; of those with inpatient methadone initiation: 19.4% vs. 0.0%). There were no significant differences in other secondary outcomes.

CONCLUSIONS

There was a strong association between ACS consultation and inpatient MOUD initiation and linkage to post-discharge MOUD. ACSs promote the delivery of evidence-based care for patients with OUD.

Reducing sickness absence: a work environment intervention in Norwegian hospitals

BACKGROUND

High rates of sickness absence is a challenge within the healthcare sector, highlighting the need for effective interventions. Despite this, limited research has been conducted on the impact of such interventions within the healthcare context. This study evaluates an intervention aimed at improving the work environment influences sickness absence rates in Norwegian hospital units. The intervention is a comprehensive framework for discovering and tailoring solutions to each units' specific needs, with a focus on employee involvement and collaboration between leader, union representatives and safety delegates.

METHODS

We employed two methodological approaches. Method 1 involved using HR-registered sickness absence data to track changes in sickness absence across all intervention units and matched control groups over a three-year period. In Method 2, we used a pre- and post-survey design in 14 intervention units, focusing on employees' job satisfaction and self-reported health.

RESULTS

The results of the intervention were mixed. There was a significant decrease in total sickness absence in the intervention units the first year after the intervention, and a significant decrease in long-term sickness absence both in the first and second year after the intervention, measured with HR registries. However, we did not see a significant larger decrease in total sickness absence in the intervention units compared to the control units and only partial support for a larger decrease in long-term absence in the intervention units. In the subsample of units that also participated in the survey, we observed significant improvements in employee job satisfaction post intervention.

CONCLUSIONS

There is a need for research on effective interventions to reduce sickness absence in the healthcare sector. "Where the shoe pinches" provides a potential methodological framework for reducing sickness absence by addressing challenges in the work environment, however with uncertain results. Further exploration is warranted to refine strategies for effectively managing sickness absence within healthcare organizations.

Association between spinal manipulative therapy and lumbar spine reoperation after discectomy: a retrospective cohort study

BACKGROUND

Patients who undergo lumbar discectomy may experience ongoing lumbosacral radiculopathy (LSR) and seek spinal manipulative therapy (SMT) to manage these symptoms. We hypothesized that adults receiving SMT for LSR at least one year following lumbar discectomy would be less likely to undergo lumbar spine reoperation compared to matched controls not receiving SMT, over two years' follow-up.

METHODS

We searched a United States network of health records (TriNetX, Inc.) for adults aged ≥ 18 years with LSR and lumbar discectomy ≥ 1 year previous, without lumbar fusion or instrumentation, from 2003 to 2023. We divided patients into two cohorts: (1) chiropractic SMT, and (2) usual care without chiropractic SMT. We used propensity matching to adjust for confounding variables associated with lumbar spine reoperation (e.g., age, body mass index, nicotine dependence), calculated risk ratios (RR), with 95% confidence intervals (CIs), and explored cumulative incidence of reoperation and the number of SMT follow-up visits.

RESULTS

Following propensity matching there were 378 patients per cohort (mean age 61 years). Lumbar spine reoperation was less frequent in the SMT cohort compared to the usual care cohort (SMT: 7%; usual care: 13%), yielding an RR (95% CIs) of 0.55 (0.35-0.85; P = 0.0062). In the SMT cohort, 72% of patients had ≥ 1 follow-up SMT visit (median = 6).

CONCLUSIONS

This study found that adults experiencing LSR at least one year after lumbar discectomy who received SMT were less likely to undergo lumbar spine reoperation compared to matched controls not receiving SMT. While these findings hold promise for clinical implications, they should be corroborated by a prospective study including measures of pain, disability, and safety to confirm their relevance. We cannot exclude the possibility that our results stem from a generalized effect of engaging with a non-surgical clinician, a factor that may extend to related contexts such as physical therapy or acupuncture.

REGISTRATION

Open Science Framework ( https://osf.io/vgrwz ).

Effects of continuum of care for maternal health service utilisation on intention to use family planning among pastoralist women of Ethiopia: a robust regression analysis and propensity score matching modelling

OBJECTIVES

This study examines the effect of continuum care for maternal health service utilisation on intention to use family planning among the pastoralist community in Ethiopia.

DESIGN

A community-based cross-sectional study.

SETTING

Data were collected from three districts of the pastoralist community of the Afar region.

PARTICIPANTS

Randomly selected 891 married pastoralist women.

PRIMARY OUTCOME

Intention to use family planning.

RESULTS

Intention to use family planning would increase (β=0.122, 95% CI: 0.036, 0.287) or by 12.2%, if all married pastoralist women received continuum of care for maternal health service utilisation compared with their counterparts. Results from the robust regression analysis indicate that intention to use family planning was higher among women who had a discussion about family planning with their husband (β=0.31, SE=0.035, p<0.001), women who possessed an electronic devices (β=0.096, SE=0.029, p<0.001) and women who had an unmet need for family planning (β=0.056, SE=0.026, p<0.000). However, intention to use family planning was lower for women who were in a polygamous marriage (β=-0.168, SE=0.065, p<0.01). There was a significant linear increase in the score of intention to use family planning for attitude towards family planning (β=0.009, SE=0.001, p<0.000), subjective norm (β=0.003, SE=0.001, p<0.003) and perceived control over family planning (β=0.002, SE=0.008, p<0.024) given other explanatory variables in the model.

CONCLUSION

Continuum of care for maternal health service utilisation increases pastoralist women's intention to use family planning. Maximising any opportunity to counsel women who come to health facilities about family planning would be vital to increase their intention to use family planning.

TRIAL REGISTRATION NUMBER

NCT03450564.

Dietary nitrate, aging and brain health: the latest evidence

PURPOSE OF REVIEW

With an increasing population age, cognitive decline and age-associated neurodegenerative diseases are becoming increasingly prevalent and burdensome in society. Dietary supplementation with inorganic nitrate, which serves as a nitric oxide precursor, has been suggested as a potential nutritional strategy to improve brain health in older adults. In this review, we discuss recent findings in this area.

RECENT FINDINGS

A number of studies have emerged in the past 12-18 months exploring the effects of dietary nitrate supplementation on cognitive function, with typically (although not exclusively) null findings emerging. This research is characterized by small, acute/short-term studies, although observational studies and longer-duration randomised controlled trials are beginning to emerge. From the limited research reporting benefits of nitrate supplementation on cognitive function, one important discovery has been the identification of a potential pathway through which nitrate could impact cognitive health, involving modulation of the oral microbiome, which warrants further investigation.

SUMMARY

Despite some promising early findings, there is currently insufficient evidence to recommend increased dietary nitrate intake for the purpose of improving brain health. However, longer-term, larger-scale trials in potentially responsive groups are warranted to provide definitive evidence in this area.