Defining the Need for Causal Inference to Understand the Impact of Social Determinants of Health: A Primer on Behalf of the Consortium for the Holistic Assessment of Risk in Transplantation (CHART)

Objective

This study aims to introduce key concepts and methods that inform the design of studies that seek to quantify the causal effect of social determinants of health (SDOH) on access to and outcomes following organ transplant.

Background

The causal pathways between SDOH and transplant outcomes are poorly understood. This is partially due to the unstandardized and incomplete capture of the complex interactions between patients, their neighborhood environments, the tertiary care system, and structural factors that impact access and outcomes. Designing studies to quantify the causal impact of these factors on transplant access and outcomes requires an understanding of the fundamental concepts of causal inference.

Methods

We present an overview of fundamental concepts in causal inference, including the potential outcomes framework and direct acyclic graphs. We discuss how to conceptualize SDOH in a causal framework and provide applied examples to illustrate how bias is introduced.

Results

There is a need for direct measures of SDOH, increased measurement of latent and mediating variables, and multi-level frameworks for research that examine health inequities across multiple health systems to generalize results. We illustrate that biases can arise due to socioeconomic status, race/ethnicity, and incongruencies in language between the patient and clinician.

Conclusions

Progress towards an equitable transplant system requires establishing causal pathways between psychosocial risk factors, access, and outcomes. This is predicated on accurate and precise quantification of social risk, best facilitated by improved organization of health system data and multicenter efforts to collect and learn from it in ways relevant to specialties and service lines.

What is visible is fixable: Visual dashboards for multi-domain assessment of organ procurement organization performance

With stakeholder focus on the United States organ procurement system, there is a need for tools that permit comparative assessment of organ procurement providers. We developed a public-facing dashboard for organ procurement organizations (OPOs), using data from multiple sources, to create an online, readily accessible visualization of OPO practice conditions and performance for the period 2010-2020. With this tool, OPOs can be compared on the CMS metric of donors procured per 100 donation-consistent deaths, as well as donation after circulatory death procurement, procurement of older and minority patient populations, procurement in smaller hospitals, and procurement of patients without a significant drug history. Patterns of higher performance were identified, and 74% of differences in overall donor procurement rates could be explained using model variables. Procurement differences were affected to a greater and more reproducible degree by OPO performance among Black and non-White patient populations, as well as in smaller hospitals, than by donation service area characteristics. Dashboards such as ours support OPOs and stakeholders in quality improvement actions, through leveraging benchmarked performance data among organ procurement clinical providers.

Identifying and understanding variation in population-based access to liver transplantation in the United States

We aimed to identify variations in liver transplant access across transplant referral regions (TRRs), accounting for differences in population characteristics and practice environments. Adult end-stage liver disease (ESLD) deaths and liver waitlist additions from 2015 to 2019 were included. The primary outcome was listing-to-death ratio (LDR). We modeled the LDR as a continuous variable and obtained adjusted LDR estimates for each TRR, accounting for clinical and demographic characteristics of ESLD decedents, socioeconomic and health care environment within the TRR, and characteristics of the transplant environment. The overall mean LDR was 0.24 (range: 0.10-0.53). In the final model, proportion of patients living in poverty and concentrated poverty was negatively associated with LDR; organ donation rate was positively associated with LDR. The R2 was 0.60, indicating that 60% of the variability in LDR was explained by the model. Approximately 40% of this variation remained unexplained and may be due to transplant center behaviors amenable to intervention to improve access to care for patients with ESLD.

A Population Health Approach to Transplant Access: Challenging the Status Quo

Transplant referral and evaluation are critical steps to waitlisting yet remain an elusive part of the transplant process. Despite calls for more data collection on pre-waitlisting steps, there are currently no national surveillance data to aid in understanding the causes and potential solutions for the extreme variation in access to transplantation. As population health scientists, epidemiologists, clinicians, and ethicists we submit that the transplant community has an obligation to better understand disparities in transplant access as a first necessary step to effectively mitigating these inequities. Our position is grounded in a population health approach, consistent with several new overarching national policy and quality initiatives. The purpose of this Perspective is to (1) provide an overview of how a population health approach should inform current multisystem policies impacting kidney transplantation and demonstrate how these efforts could be enhanced with national data collection on pre-waitlisting steps; (2) demonstrate the feasibility and concrete next steps for pre-waitlisting data collection; and (3) identify potential opportunities to use these data to implement effective population-level interventions, policies, and quality measures to improve equity in access to kidney transplantation.

Examining utilization of kidneys as a function of procurement performance

Questions have arisen around new metrics for organ procurement organizations (OPO) due to the perception that low-performing OPOs may be limited by local centers' acceptance of marginal organs. We reviewed 2013-2019 Organ Procurement and Transplantation Network (OTPN) and National Centers for Health Statistics (NCHS) data to explore the relationship between objectively measured OPO performance and utilization of deceased donor kidneys. We found that although donor recovery declined with rising age and kidney donor profile index (KDPI), OPO performance differences were evident within each age/KDPI group. By contrast, the number of discards per donor did not vary with OPO performance. Centers in donor service areas (DSAs) with lower-performing OPOs had higher local utilization and greater import of high-KDPI kidneys than did those with higher-performing OPOs. Lower rates of donor availability relative to waitlist additions may contribute to observed center acceptance behavior. Differences in center-level performance were highly visible in Scientific Registry of Transplant Recipients (SRTR) organ acceptance metrics, while SRTR OPO metrics did not detect large or persistent variation in procurement performance. Cumulatively, our findings suggest that objective measures of procurement performance can inform discussions of organ utilization, allowing for alignment of metrics in all elements of the procurement-transplantation system.

Time to Surgical Treatment and Facility Characteristics as Potential Drivers of Racial Disparities in Breast Cancer Mortality

BACKGROUND

Black women are more likely to die of breast cancer than White women. This study evaluated the contribution of time to primary surgical management and surgical facility characteristics to racial disparities in breast cancer mortality among both Black and White women.

METHODS

The study identified 2224 Black and 3787 White women with a diagnosis with stages I to III breast cancer (2010-2014). Outcomes included time to surgical treatment (> 30 days from diagnosis) and breast cancer mortality. Odds ratios (ORs) and 95% confidence intervals (CIs) associating surgical facility characteristics with surgical delay were computed, and Cox proportional hazards regression was used to compute hazard ratios (HRs) and 95% CIs associating delay and facility characteristics with breast cancer mortality.

RESULTS

Black women were two times more likely to have a surgical delay (OR, 2.15; 95% CI, 1.92-2.41) than White women. Racial disparity in surgical delay was least pronounced among women treated at a non-profit facility (OR, 1.95; 95% CI, 1.70-2.25). The estimated mortality rate for Black women was two times that for White women (HR, 2.00; 95% CI, 1.83-2.46). Racial disparities in breast cancer mortality were least pronounced among women who experienced no surgical delay (HR, 1.81; 95% CI, 1.28-2.56), received surgery at a government facility (HR, 1.31; 95% CI, 0.76-2.27), or underwent treatment at a Commission on Cancer-accredited facility (HR, 1.82; 95% CI, 1.38-2.40).

CONCLUSIONS

Black women were more likely to experience a surgical delay and breast cancer death. Persistent racial disparities in breast cancer mortality were observed across facility characteristics except for government facilities.

Biliary Complications Following Adult Deceased Donor Liver Transplantation: Risk Factors and Implications at a High-volume US Center

Biliary leaks and anastomotic strictures comprise the majority of biliary complications (BCs) following liver transplantation (LT). Currently, there are few large contemporary case series of BCs in adult deceased donor liver transplant (DDLT) recipients in the literature. The purpose of this study was to examine the pretransplant and intraoperative risk factors associated with BCs at a high-volume tertiary care center and determine the impact of these BCs on their posttransplant course and long-term transplant outcomes.

METHODS

We retrospectively reviewed all adult patients undergoing a DDLT from a donor after brain death (DBD) at Emory University between January 2015 and December 2019.

RESULTS

A total of 647 adult patients underwent DDLT from a DBD during the study period and were included in analyses. The median length of follow-up posttransplant was 2.5 y. There were a total of 27 bile leaks (4.2%) and 69 biliary strictures (10.7%). Recipient age and cold ischemic time were identified as risk factors for biliary leak, whereas alcoholic cirrhosis as transplant indication was a risk factor for biliary stricture. Placement of a biliary stent was associated with the development of both biliary leaks and anastomotic strictures. Posttransplant, biliary leaks were a significant risk factor for future episodes of acute rejection but did not impact overall survival. In contrast, biliary strictures were associated with a significantly reduced overall survival at 1- and 4-y post DDLT.

CONCLUSIONS

BCs are a major source of morbidity and mortality following DDLT, with strictures and leaks associated with distinct posttransplant complications.

Public discourse and policy change: Absence of harm from increased oversight and transparency in OPO performance

The Centers for Medicare and Medicaid Services announced changes to the Final Rule for organ procurement organizations (OPOs) in November 2020, after a 23-month period of public debate. One concern among transplant stakeholders was that public focus on OPO underperformance would harm deceased donation. Using CDC-WONDER data, we studied whether donation performance dropped during the era of public debate about OPO reform (December 2018-February 2020). Overall OPO performance as measured relative to cause, age, and location-consistent deaths rose by 12.3% in 2019, compared to a median annual change of 2.5% 2009-2019. Organ recoveries exceeded seasonally adjusted forecasts by 4.2% in the first half of 2019, by 8.1% following the Executive Order issuing a mandate for OPO metric reform, and by 14.1% between the Notice of Public Rule Making and the onset of COVID-19-related systemic disruptions. We describe changes in donor phenotype in the period of increased performance; improvement was greatest for older and donation after cardiac death (DCD) donors, and among decedents who did not have a drug-related mechanism of death. In summary, performance during an era of intense public debate and proposed regulatory changes yielded 692 additional donors over expectations, and no detriment to organ donation was observed.

Racial and Ethnic Differences and Clinical Outcomes of COVID-19 Patients Presenting to the Emergency Department

BACKGROUND

Since the introduction of remdesivir and dexamethasone for severe COVID-19 treatment, few large multi-hospital system US studies have described clinical characteristics and outcomes of minority COVID-19 patients who present to the emergency department (ED).

METHODS

This cohort study from the Cerner Real World Database (87 US health systems) from December 1, 2019 to September 30, 2020 included PCR-confirmed COVID-19 patients who self-identified as non-Hispanic Black (Black), Hispanic White (Hispanic), or non-Hispanic White (White). The main outcome was hospitalization among ED patients. Secondary outcomes included mechanical ventilation, intensive care unit care, and in-hospital mortality. Descriptive statistics and Poisson regression compared sociodemographics, comorbidities, receipt of remdesivir, receipt of dexamethasone, and outcomes by racial/ethnic groups and geographic region.

RESULTS

94,683 COVID-19 patients presented to the ED. Blacks comprised 26.7% and Hispanics 33.6%. Nearly half (45.1%) of ED patients presented to hospitals in the South. 31.4% (n=29,687) were hospitalized. Lower proportions of Blacks were prescribed dexamethasone (29.4%; n=7,426) compared to Hispanics (40.9%; n=13,021) and Whites (37.5%; n=14,088). Hospitalization risks, compared to Whites, were similar in Blacks (Risk Ratio (RR)=0.94; 95% CI:0.82, 1.08; p=0.4)) and Hispanics RR=0.99 (95% CI:0.81, 1.21; p=0.91), but risk of in-hospital mortality was higher in Blacks, RR=1.18 (95% CI:1.06, 1.31; p=0.002) and Hispanics, RR=1.28 (95% CI: 1.13, 1.44; p < 0.001).

CONCLUSIONS

Minority patients were overrepresented among COVID-19 ED patients, and while they had similar risks of hospitalization as Whites, in-hospital mortality risk was higher. Interventions targeting upstream social determinants of health are needed to reduce racial/ethnic disparities in COVID-19.