Body Mass Index in Lung Transplant Candidates: A Contra-indication to Transplant or Not?

Global Leadership Initiative on Malnutrition-Diagnosed Malnutrition in Lung Transplant Candidates

BACKGROUND AND AIMS

Malnutrition in lung transplantation (LT) candidates increases postoperative morbidity and mortality. Early diagnosis of malnutrition could attenuate adverse prognostic factors. This study aimed to assess the prevalence of nutritional risk and malnutrition using GLIM criteria in LT candidates and clinically characterize those with malnutrition.

METHODS

A prospective longitudinal study was conducted from 2000 to 2020 of LT candidates who underwent complete nutritional assessment (nutritional screening, anthropometry, bioelectrical impedance, blood laboratory tests and malnutrition diagnosis using GLIM criteria).

RESULTS

Obstructive diseases (45.6%), interstitial diseases (36.6%) and cystic fibrosis/non-cystic fibrosis bronchiectasis (15.4%) were the main conditions assessed for LT. Of the 1060 candidates evaluated, 10.6% were underweight according to BMI, 29% were at risk of malnutrition and 47% were diagnosed with malnutrition using GLIM criteria. Reduced muscle mass was the most frequent GLIM phenotypic criterion. Malnutrition was more prevalent in patients with cystic fibrosis/non-cystic fibrosis bronchiectasis (84.5%) and obstructive (45.4%) and interstitial (31.3%) diseases. GLIM criteria detected some degree of malnutrition in all diseases requiring LT and identified patients with higher CRP levels and worse respiratory function, anthropometric measurements and visceral protein and lipid profiles.

CONCLUSIONS

LT candidates present a high prevalence of malnutrition using the GLIM algorithm. GLIM criteria detected malnutrition in all diseases requiring LT and defined patients with worse clinical-analytical profiles.

Impact of changes in skeletal muscle mass and quality during the waiting time on outcomes of lung transplantation

INTRODUCTION

The association of changes in skeletal muscle mass and quality during the waiting time with outcomes of lung transplantation (LT) remains unclear. We aimed to examine the association of changes in skeletal muscle mass and quality during the waiting time, as well as preoperative skeletal muscle mass and quality, with outcomes of LT.

METHODS

This study included individuals who underwent LT from brain-dead donors. Skeletal muscle mass (cm2 /m2 ) and quality (mean Hounsfield units [HU]) of the erector spinae muscle at the 12th thoracic level were evaluated using computed tomography. Preoperative skeletal muscle mass and quality, and their changes during the waiting time were calculated. We evaluated the associations among mechanical ventilation (MV) duration, intensive care unit (ICU) length of stay (LOS), hospital LOS, 6-minute walk distance at discharge, and 5-year survival after LT.

RESULTS

This study included 98 patients. The median waiting time was 594.5 days (interquartile range [IQR], 355.0-913.0). The median changes in skeletal muscle mass and quality were -4.4% (IQR, -13.3-3.1) and -2.9% (IQR, -16.0-4.1), respectively. Severe low skeletal muscle mass at LT was associated with prolonged ICU LOS (B = 8.46, 95% confidence interval [CI]: .51-16.42) and hospital LOS (B = 36.00, 95% CI: 3.23-68.78). Pronounced decrease in skeletal muscle mass during the waiting time was associated with prolonged MV duration (B = 7.85, 95% CI: .89-14.81) and ICU LOS (B = 7.97, 95% CI: .83-15.10).

CONCLUSION

Maintaining or increasing skeletal muscle mass during the waiting time would be beneficial to improve the short-term outcomes of LT.

Lung transplantation outcomes in underweight recipients: A single center experience

Background

Current guidelines recommend a body mass index (BMI) of 16 kg/m² as the minimum threshold for lung transplantation, despite mixed evidence on outcomes in underweight patients. The current study aimed to describe survival outcomes of underweight patients who underwent lung transplantation at a single center.

Methods

This retrospective observational study included adult lung transplant recipients who underwent transplantation for the first time between March 2010 and March 2022 at King Faisal Specialist Hospital and Research Center and excluded patients with obesity. We defined an underweight status as a BMI <17 kg/m².

Results

Forty-eight of the 202 lung transplant recipients were underweight at the time of surgery. The underweight patients had similar lengths of hospital (p = 0.53) and intensive care unit (p = 0.81) stays compared to other patients. Thirty-three percent of underweight patients had died within 5-year follow-up, compared to 34% of patients who were not underweight. There was no significant difference in mortality risk between underweight patients and patients with normal BMIs in our multivariable Cox regression model (adjusted HR 1.57, 95%CI: 0.77-3.20, p = 0.21). Exploratory analyses revealed that a pre-transplant BMI <13 kg/m² was associated with a trend towards increased 5-year mortality (adjusted HR 4.00, 95%CI: 0.87-18.35, p = 0.07).

Conclusions

Our findings suggest that patients with BMIs of 13-17 kg/m² may be candidates for lung transplantation. Large multi-center cohort studies are needed to confirm the lower BMI limit for safely transplanting patients.

Computed tomography body composition and clinical outcomes following lung transplantation in cystic fibrosis

BACKGROUND

Low muscle mass is common in patients approaching lung transplantation and may be linked to worse post-transplant outcomes. Existing studies assessing muscle mass and post-transplant outcomes include few patients with cystic fibrosis (CF).

METHODS

Between May 1993 and December 2018, 152 adults with CF received lung transplants at our institution. Of these, 83 met inclusion criteria and had usable computed tomography (CT) scans. Using Cox proportional hazards regression, we evaluated the association between pre-transplant thoracic skeletal muscle index (SMI) and our primary outcome of death after lung transplantation. Secondary outcomes, including days to post-transplant extubation and post-transplant hospital and intensive care unit (ICU) length of stay, were assessed using linear regression. We also examined associations between thoracic SMI and pre-transplant pulmonary function and 6-min walk distance.

RESULTS

Median thoracic SMI was 26.95 cm²/m² (IQR 23.97, 31.32) for men and 22.83 cm²/m² (IQR 21.27, 26.92) for women. There was no association between pre-transplant thoracic SMI and death after transplant (HR 1.03; 95% CI 0.95, 1.11), days to post-transplant extubation, or post-transplant hospital or ICU length of stay. There was an association between pre-transplant thoracic SMI and pre-transplant FEV1% predicted (b = 0.39; 95% CI 0.14, 0.63), with higher SMI associated with higher FEV1% predicted.

CONCLUSIONS

Skeletal muscle index was low for men and women. We did not identify a significant relationship between pre-transplant thoracic SMI and post-transplant outcomes. There was an association between thoracic SMI and pre-transplant pulmonary function, confirming the potential value of sarcopenia as a marker of disease severity.

External validity of machine learning-based prognostic scores for cystic fibrosis: A retrospective study using the UK and Canadian registries

Precise and timely referral for lung transplantation is critical for the survival of cystic fibrosis patients with terminal illness. While machine learning (ML) models have been shown to achieve significant improvement in prognostic accuracy over current referral guidelines, the external validity of these models and their resulting referral policies has not been fully investigated. Here, we studied the external validity of machine learning-based prognostic models using annual follow-up data from the UK and Canadian Cystic Fibrosis Registries. Using a state-of-the-art automated ML framework, we derived a model for predicting poor clinical outcomes in patients enrolled in the UK registry, and conducted external validation of the derived model using the Canadian Cystic Fibrosis Registry. In particular, we studied the effect of (1) natural variations in patient characteristics across populations and (2) differences in clinical practice on the external validity of ML-based prognostic scores. Overall, decrease in prognostic accuracy on the external validation set (AUCROC: 0.88, 95% CI 0.88-0.88) was observed compared to the internal validation accuracy (AUCROC: 0.91, 95% CI 0.90-0.92). Based on our ML model, analysis on feature contributions and risk strata revealed that, while external validation of ML models exhibited high precision on average, both factors (1) and (2) can undermine the external validity of ML models in patient subgroups with moderate risk for poor outcomes. A significant boost in prognostic power (F1 score) from 0.33 (95% CI 0.31-0.35) to 0.45 (95% CI 0.45-0.45) was observed in external validation when variations in these subgroups were accounted in our model. Our study highlighted the significance of external validation of ML models for cystic fibrosis prognostication. The uncovered insights on key risk factors and patient subgroups can be used to guide the cross-population adaptation of ML-based models and inspire new research on applying transfer learning methods for fine-tuning ML models to cope with regional variations in clinical care.

A GLIMmer of insight into lung transplant nutrition: Enhanced detection of malnutrition in lung transplant patients using the GLIM criteria

BACKGROUND & AIMS

The Global Leadership Initiative on Malnutrition (GLIM) is a novel framework for diagnosing malnutrition and requires evaluation in wide-ranging clinical settings. This study aimed to assess the prevalence of malnutrition and its phenotypic characteristics among lung transplantation (LTx) candidates comparing GLIM to International Classification of Diseases, 10th Revision (ICD-10) criteria.

METHODS

A retrospective analysis was conducted of all adult patients assessed for LTx in a one-year period. Phenotypic criteria included body mass index (BMI), unintentional loss of weight (LOW) over a 12-month period and fat-free mass index (FFMI) using bioelectrical impedance analysis (BIA). Systemic inflammation associated with severe end-stage lung disease met GLIM's etiological criterion. Diagnosis of malnutrition, and its severity, were classified according to each of GLIM and ICD-10.

RESULTS

Of 130 patients, 112 (86%) had all data to classify malnutrition. Malnutrition prevalence according to GLIM was 59%, which was markedly greater than using ICD-10 criteria (26%). Half of the LTx patients were moderately malnourished using GLIM, compared to 19% using ICD-10. A similar proportion were severely malnourished using GLIM (9%) and ICD-10 (7%). Fat-free mass (FFM) depletion (47% of all patients) was a major contributor to GLIM-malnutrition. Over 60% of LTx patients with GLIM-malnutrition were not detected as malnourished using ICD-10 criteria.

CONCLUSION

Malnutrition diagnosis using GLIM was higher than using ICD-10 in LTx patients, primarily attributable to the incorporation of quantitative evaluation of FFM depletion. This highlights the utility of the GLIM framework and the importance of including body composition in malnutrition assessment.

Frailty in Lung Transplantation - Candidate Assessment and Optimization

The concept of frailty has gained considerable interest in clinical solid organ transplantation over the past decade. Frailty as a phenotypic construct to describe a patient's risk from biologic stresses, has an impact on posttransplant survival. There is keen interest in characterizing frailty in lung transplantation, both to determine which patients are suitable candidates for listing and also to prepare for their care in the aftermath of lung transplantation. Here we review the current status of research on frailty in lung transplant candidates and recipients. This review will highlight areas of uncertainty for frailty in clinical lung transplantation which are likely to impact the state-of-the-art in the field for the next decade.

Medical Contraindications to Transplant Listing in the USA: A Survey of Adult and Pediatric Heart, Kidney, Liver, and Lung Programs

INTRODUCTION

Listing practices for solid organ transplantation are variable across programs in the USA. To better characterize this variability, we performed a survey of psychosocial listing criteria for pediatric and adult heart, lung, liver, and kidney programs in the USA. In this manuscript, we report our results regarding listing practices with respect to obesity, advanced age, and HIV seropositivity.

METHODS

We performed an online, forced-choice survey of adult and pediatric heart, kidney, liver, and lung transplant programs in the USA.

RESULTS

Of 650 programs contacted, 343 submitted complete responses (response rate = 52.8%). Most programs have absolute contraindications to listing for BMI > 45 (adult: 67.5%; pediatric: 88.0%) and age > 80 (adult: 55.4%; pediatric: not relevant). Only 29.5% of adult programs and 25.7% of pediatric programs consider HIV seropositivity an absolute contraindication to listing. We found that there is variation in absolute contraindications to listing in adult programs among organ types for BMI > 45 (heart 89.8%, lung 92.3%, liver 49.1%, kidney 71.9%), age > 80 (heart 83.7%, lung 76.9%, liver 68.4%, kidney 29.2%), and HIV seropositivity (heart 30.6%, lung 59.0%, kidney 16.9%, liver 28.1%).

CONCLUSIONS

We argue that variability in listing enhances access to transplantation for potential recipients who have the ability to pursue workup at different centers by allowing different programs to have different risk thresholds. Programs should remain independent in listing practices, but because these practices differ, we recommend transparency in listing policies and informing patients of reasons for listing denial and alternative opportunities to seek listing at another program.

Determinants of survival in lung transplantation patients with idiopathic pulmonary fibrosis: a retrospective cohort study

Survival after lung transplantation (LTx) for idiopathic pulmonary fibrosis (IPF) is worse compared to other indications for LTx. We investigated the effect of several pretransplant variables including the use of pretransplant corticosteroids (CS) on post-transplant graft and chronic lung allograft dysfunction (CLAD)-free survival and functional testing (maximum inspiratory and expiratory pressure, six-minute walk test, quadriceps and hand pinch force) in a small cohort of IPF patients. We retrospectively compared two groups of IPF patients (n = 36 on CS vs. n = 18 not on CS) who underwent LTx between 2000 and 2016. Analysis of 54 IPF-LTx patients showed no significant effect on graft survival or functional tests except for maximum inspiratory pressure (P = 0.033) between these two groups (all LTx patients, CS vs. no CS). Regression analysis showed significant impact of procedure with a hazard ratio of 0.423 (CI 95% 0.194, 0.924) favoring sequential single LTx (SSLTx) compared to single lung transplantation (SLTx). When analyzing only the 40 SSLTx patients, corticosteroid-free patients showed significantly better graft survival compared to patients on CS (P = 0.045) and CLAD-free survival (P = 0.019). The possible detrimental effect of corticosteroid therapy before LTx was demonstrated in this cohort of SSLTx patients, which questions the use of corticosteroids in a pretransplantation setting.

The Impact of Waiting List BMI Changes on the Short-term Outcomes of Lung Transplantation

BACKGROUND

Obesity and underweight are associated with a higher postlung transplantation (LTx) mortality. This study aims to assess the impact of the changes in body mass index (BMI) during the waiting period for LTx on early postoperative outcomes.

METHODS

Medical records of 502 consecutive cases of LTx performed at our institution between 1999 and 2015 were reviewed. Patients were stratified per change in BMI category between pre-LTx assessment (candidate BMI) and transplant BMI as follows: A-candidate BMI, less than 18.5 or 18.5 to 29.9 and transplant BMI, less than 18.5; B-candidate BMI, less than 18.5 and transplant BMI, 18.5 to 29.9; C-candidate BMI, 18.5 to 29.9 and transplant BMI, 18.5 to 29.9; D-candidate BMI, 30 or greater and transplant BMI, 18.5 to 29.9; and E-candidate BMI, 30 or greater or 18.5 to 29.9 and transplant BMI, 30 or greater. Our primary outcome was in-hospital mortality and secondary outcomes were length of mechanical ventilation, intensive care unit length of stay (LOS), hospital LOS and postoperative complications.

RESULTS

BMI variation during the waiting time was common, as 1/3 of patients experienced a change in BMI category. Length of mechanical ventilation (21 days vs 9 days; P = 0.018), intensive care unit LOS (26 days vs 15 days; P = 0.035), and rates of surgical complications (76% vs 44%; P = 0.018) were significantly worse in patients of group E versus group D. Obese candidates who failed to decrease BMI less than 30 by transplant exhibited an increased risk of postoperative mortality (odds ratio, 2.62; 95% confidence interval, 1.01-6.48) compared with patients in group C. Pre-LTx BMI evolution had no impact on postoperative morbidity and mortality in underweight patients.

CONCLUSIONS

Our results suggest that obese candidates with an unfavorable pretransplant BMI evolution are at greater risk of worse post-LTx outcomes.

Association of body mass index with lung transplantation survival in the United States following implementation of the lung allocation score

BACKGROUND

The association of body mass index (BMI) with survival after lung transplantation remains controversial, owing to conflicting evidence in the literature. Previous reports have used traditional BMI categories, included patients who underwent transplantation before implementation of the lung allocation score (LAS), or were limited by single-center experiences. Here we evaluated the association of individual BMI units with short-term and long-term mortality in a large national database following implementation of the LAS.

METHODS

The Scientific Registry of Transplant Recipients database was used to collect data for 17,233 adult lung transplantations performed between May 2005 and June 2016. The primary outcome was all-cause mortality at 90 days and 1 year posttransplantation. Logistic regression modeling was used to independently predict mortality per BMI unit, adjusting for donor and recipient factors.

RESULTS

BMI was an independent predictor of mortality at both 90 days and 1 year. At 90 days, a BMI of 25 was associated with the lowest predicted probability of death (0.053; 95% confidence interval [CI], 0.047-0.049), with increased odds of mortality at BMI ≤20 and ≥28. At 1 year, a BMI of 26 was associated with the lowest predicted probability of death (0.12; 95% CI, 0.11-0.13), with increased odds of mortality at BMI ≤24 and ≥28.

CONCLUSIONS

Each individual BMI unit has a quantifiable effect on posttransplantation survival, and the patterns of effect do not fit into the predefined BMI categories. The mortality risk associated with BMI should be considered by transplant centers when making listing decisions and by regulatory bodies for estimating expected outcomes.

Recipient selection process and listing for lung transplantation

Lung transplantation remains the ultimate treatment option for selected patients with end-stage (cardio) pulmonary disease. Given the current organ shortage, it is without any doubt that careful selection of potential transplant candidates is essential as this may greatly influence survival after the procedure. In this paper, we will review the current guidelines for referral and listing of lung transplant candidates in general, and in more depth for the specific underlying diseases. Needless to state that these are not absolute guidelines, and that decisions depend upon center's activity, waiting list, etc. Therefore, every patient should be discussed with the transplant center before any definite decision is made to accept or decline a patient for lung transplantation.

Pretransplant frailty is associated with decreased survival after lung transplantation

BACKGROUND

Frailty is a condition of increased vulnerability to adverse health outcomes. Although frailty is an important prognostic factor for many conditions, the effect of frailty on mortality in lung transplantation is unknown. Our objective was to assess the association of frailty with survival after lung transplantation.

METHODS

We performed a retrospective cohort analysis of all adult lung transplant recipients at our institution between 2002 and 2013. Frailty was assessed using the frailty deficit index, a validated instrument that assesses cumulative deficits for up to 32 impairments and measures the proportion of deficits present (with frailty defined as >0.25). We examined the association between frailty and survival, adjusting for age, sex, and bilateral (vs single) lung transplant using Cox proportional hazard regression models.

RESULTS

Among 144 lung transplant patients, 102 (71%) completed self-reported questionnaires necessary to assess the frailty deficit index within 1 year before lung transplantation. Frail patients (n = 46) had an increased risk of death, with an adjusted hazard ratio (HR) of 2.24 (95% confidence interval [CI], 1.22-4.19; p = 0.0089). Frailty was not associated with an increased duration of mechanical ventilation (median, 2 vs 2 days; p = 0.26), intensive care unit length of stay (median, 7.5 vs 6 days; p = 0.36) or hospital length of stay after transplantation (median, 14 vs 10.5 days; p = 0.26).

CONCLUSIONS

Pre-transplant frailty was independently associated with decreased survival after lung transplantation. Pre-transplant frailty may represent an important area for intervention to improve candidate selection and lung transplant outcomes.

Overweight-mortality paradox and impact of six-minute walk distance in lung transplantation

Overweight–mortality paradox and impact of six-minute walk distance (SMWD) in lung transplantation