The Past, Present, and Near Future of Lung Allocation in the United States

The first official donor lung allocation system in the United States was initiated by the United Network of Organ Sharing in 1990. The initial policy for lung allocation was simple with donor lungs allocated based on ABO match and the amount of time the candidates accrued on the waiting list. Donor offers were first given to candidates' donor service area. In March 2005, the implementation of the lung allocation score (LAS) was the major change in organ allocation. International adoption of the LAS-based allocation system can be seen worldwide.

Place-based heterogeneity in lung transplant recipient outcomes

Place is defined as a social or environmental area of residence with meaning to a patient. We hypothesize there is an association between place and the clinical outcomes of lung transplant recipients in the United States. In a retrospective cohort study of transplants between January 1, 2010, and December 31, 2019, in the Scientific Registry of Transplant Recipients, multivariable Cox regression models were used to test the association between place (through social and environmental factors) with readmission, lung rejection, and survival. Among 18,465 recipients, only 20% resided in the same county as the transplant center. Recipients from the most socially vulnerable counties when compared to the least vulnerable were more likely to have COPD as a native disease, Black or African American race, and travel long distances to reach a transplant center. Higher local life expectancy was associated with lower likelihood for readmission (odds ratio [OR] = 0.90, 95% confidence interval [CI]: 0.84, 0.98, p = .01). Higher social vulnerability was associated with a higher likelihood of lung rejection (OR = 1.37, [CI]: 1.07, 1.76, p = .01). There was no association of residence with posttransplant survival. Recipient place-based factors were associated with complications and processes of care after transplant and warrant further investigation.

Lung transplant waitlist outcomes in the United States and patient travel distance

There is a broad range of patient travel distances to reach a lung transplant hospital in the United States. Whether patient travel distance is associated with waitlist outcomes is unknown. We present a cohort study of patients listed between January 1, 2006 and May 31, 2017 using the Scientific Registry of Transplant Recipients. Travel distance was measured from the patient's permanent zip code to the transplant hospital using shared access signature URL access to Google Maps, and assessed using multivariable competing risk regression models. There were 22 958 patients who met inclusion criteria. Median travel distance was 69.7 miles. Among patients who traveled > 60 miles, 41.2% bypassed a closer hospital and sought listing at a more distant hospital. In the adjusted models, when compared to patients who traveled ≤60 miles, patients who traveled >360 miles had a 27% lower subhazard ratio (SHR) for waitlist removal (SHR 0.73, 95% confidence interval [CI]: 0.60, 0.89, P = .002), 16% lower subhazard for waitlist death (SHR 0.84; 95% CI 0.73-0.95, P = .07), and 13% increased likelihood for transplant (SHR 1.13, 95% CI: 1.07, 1.20, P < .001). Many patients bypassed the nearest transplant hospital, and longer patient travel distance was associated with favorable waitlist outcomes.

COVID-19 and lung transplant patients

COVID-19 is a novel respiratory disease leading to high rates of acute respiratory failure requiring hospital admission. It is unclear if specific patient populations such as lung transplant patients are at higher risk for COVID-19. Some reports suggest that transplant patients may not be at higher risk if proper social distancing and preventive measures are employed. Efforts to ensure the safety of wait-listed patients, transplant recipients, and healthcare workers are underway. Recommendations for the care of lung transplant patients during the COVID-19 pandemic are discussed and will likely change as the pandemic evolves.

Perspectives on donor lung allocation from both sides of the Atlantic: The United States

Donor lung allocation in the United States focuses on decreasing waitlist mortality and improving recipient outcomes. The implementation of allocation policy to match deceased donor lungs to waitlisted patients occurs through a unique partnership between government and private organizations, namely the Organ Procurement and Transplantation Network under the Department of Health and Human Services and the United Network for Organ Sharing. In 2005, the donor lung allocation algorithm shifted toward the prioritization of medical urgency of waitlisted patients instead of time accrued on the waitlist. This led to the Lung Allocation Score, which weighs over a dozen clinical variables to predict a 1-year estimate of survival benefit, and is used to prioritize waitlisted patients. In 2017, the use of local allocation boundaries was eliminated in favor of a 250 nautical mile radius from the donor hospital as the first unit of distance used in allocation. The next upcoming iteration of donor allocation policy is expected to use a continuous distribution algorithm where all geographic boundaries are eliminated. There are additional opportunities to improve donor lung allocation, such as for patients with high antibody titers with access to a limited number of donors.

Extremes of Age Decrease Survival in Adults After Lung Transplant

BACKGROUND

Age has been implicated as a factor in the plateau of long-term survival after lung transplant.

METHODS

We used data from the Scientific Registry of Transplant Recipients to identify all recipients of lung transplant aged ≥18 years of age between January 1, 2006, and February 19, 2015. A total of 14,253 patients were included in the analysis. Survival was estimated using a nonproportional hazard model and random-survival forest methodology was used to examine risk factors for death. Final selection of model variables was performed using bootstrap aggregation. Age was analyzed as both a continuous and categorical variable (age <30, 30-55, and >55 years). Risk factors for death were obtained for the entire cohort and additional age-specific risk factors were identified for each age category.

RESULTS

The median age at transplant was 59 years. There were 1,098 (7.7%) recipients <30 years, 4,201 (29.5%) 30 to 55 years, and 8,954 (62.8%) >55 years of age. Age was the most significant risk factor for death at all time-points following transplant and its impact becomes more prominent as time from transplant increases. Risk factors for death for all patients included extremes of age, higher creatinine, single lung transplant, hospitalization before transplant, and increased bilirubin. Risk factors for death differed by age with social determinants of health disproportionately affecting survival for those in the youngest age category.

CONCLUSIONS

The youngest and oldest adult recipients experienced the lowest posttransplant survival through divergent pathways that may present opportunities for intervention to improve survival after lung transplant.

The Association Between Lung Recipient Travel Distance and Posttransplant Survival

Introduction:

Recipient travel distance may be an unrecognized burden in lung transplantation.

Design:

Retrospective single-center cohort study of all adult (≥18 years) first-time lung-only transplants from January 1, 2010, until February 28, 2017. Recipient distance to transplant center was calculated using the linear distance from the recipient’s home zip code to the Cleveland Clinic in Cleveland, Ohio.

Results:

569 recipients met inclusion criteria. Posttransplant graft survival was 85%, 88%, 91%, and 91% at 1 year and 49%, 52%, 57%, and 56% at 5 years posttransplant for recipient travel distances of ≤50, >50 to ≤250, >250 to ≤500, and >500 miles, respectively ( P = .10).

Discussion:

We found no significant relationship between recipient travel distance and posttransplant graft survival. In carefully selected recipients, travel distance is not a significant barrier to successful posttransplant outcomes which may be important for patient decision-making and donor allocation policy. These data should be validated in a national cohort.

Broader Geographic Sharing of Pediatric Donor Lungs Improves Pediatric Access to Transplant

US pediatric transplant candidates have limited access to lung transplant due to the small number of donors within current geographic boundaries, leading to assertions that the current lung allocation system does not adequately serve pediatric patients. We hypothesized that broader geographic sharing of pediatric (adolescent, 12-17 years; child, <12 years) donor lungs would increase pediatric candidate access to transplant. We used the thoracic simulated allocation model to simulate broader geographic sharing. Simulation 1 used current allocation rules. Simulation 2 offered adolescent donor lungs across a wider geographic area to adolescents. Simulation 3 offered child donor lungs across a wider geographic area to adolescents. Simulation 4 combined simulations 2 and 3. Simulation 5 prioritized adolescent donor lungs to children across a wider geographic area. Simulation 4 resulted in 461 adolescent transplants per 100 patient-years on the waiting list (range 417-542), compared with 206 (range 180-228) under current rules. Simulation 5 resulted in 388 adolescent transplants per 100 patient-years on the waiting list (range 348-418) and likely increased transplant rates for children. Adult transplant rates, waitlist mortality, and 1-year posttransplant mortality were not adversely affected. Broader geographic sharing of pediatric donor lungs may increase pediatric candidate access to lung transplant.

Assessing the causal effect of organ transplantation on the distribution of residual lifetime

Because the number of patients waiting for organ transplants exceeds the number of organs available, a better understanding of how transplantation affects the distribution of residual lifetime is needed to improve organ allocation. However, there has been little work to assess the survival benefit of transplantation from a causal perspective. Previous methods developed to estimate the causal effects of treatment in the presence of time-varying confounders have assumed that treatment assignment was independent across patients, which is not true for organ transplantation. We develop a version of G-estimation that accounts for the fact that treatment assignment is not independent across individuals to estimate the parameters of a structural nested failure time model. We derive the asymptotic properties of our estimator and confirm through simulation studies that our method leads to valid inference of the effect of transplantation on the distribution of residual lifetime. We demonstrate our method on the survival benefit of lung transplantation using data from the United Network for Organ Sharing.

An acute change in lung allocation score and survival after lung transplantation: a cohort study

BACKGROUND

Lung transplantation is an effective treatment for patients with advanced lung disease. In the United States, lungs are allocated on the basis of the lung allocation score (LAS), a composite measure of transplantation urgency and utility. Clinical deteriorations result in increases to the LAS; however, whether the trajectory of the LAS has prognostic significance is uncertain.

OBJECTIVE

To determine whether an acute increase in the LAS before lung transplantation is associated with reduced posttransplant survival.

DESIGN

Retrospective cohort study of adult lung transplant recipients listed for at least 30 days between 4 May 2005 (LAS implementation) and 31 December 2010 in the United Network for Organ Sharing registry. An acute increase in the LAS was defined as an LAS change (LASΔ) greater than 5 units between the 30 days before and the time of transplantation. Multivariable Cox proportional hazard models were used to examine the relationship between an LASΔ >5 and posttransplant graft survival.

SETTING

All U.S. lung transplantation centers.

PATIENTS

5749 lung transplant recipients.

MEASUREMENTS

Survival time after lung transplantation.

RESULTS

702 (12.2%) patients experienced an LASΔ >5. These patients had significantly worse posttransplant survival (hazard ratio, 1.31 [95% CI, 1.11 to 1.54]; P = 0.001]) after adjustment for the LAS at transplantation (LAS-T) and other clinical covariates. The effect of an LASΔ >5 was independent of the LAS-T, underlying diagnosis, center volume, or donor characteristics.

LIMITATION

Analysis was based on center-reported data.

CONCLUSION

An acute increase in LAS before transplantation is associated with posttransplant survival after adjustment for LAS-T. Further emphasis on serial assessment of the LAS could improve the ability to offer accurate prediction of survival after transplantation.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Influenza-like symptoms in the college dormitory environment: a survey taken during the 1999-2000 influenza season

The effect of dormitory environments on the transmission of the influenza virus in college students is not well understood. During the 1999-2000 flu season, dormitory residents at a college campus in Chicago were surveyed about their living conditions and influenza-like symptoms (ILS). The survey had a 42 percent response ratio (721 of 1,704). Students who had > or = 50 percent carpeting in their room were at significantly lower risk for ILS (p = .02). Although the risk of ILS increased for roommates who shared sleeping quarters compared with those who slept in different rooms (RR = 4.3), the difference was not statistically significant. No evidence was found that ILS risk was affected by washroom, laundry, or dining settings, or by demographics, including gender or year in college. The survey instrument detected strong relations between ILS and the dormitory room environment, in contrast with other settings in the dormitory. Further research on transmission may focus on the room environment.