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What's New


                                                                                  Lung Transplantation: Version 7.0

What’s New?

1. Updated first year billed charges from Milliman:


See tables at the end of this Quick Reference Guide.  

1. Lung Allocation System [1]

It has now been about 10 years since the major revision of lung allocation, replacing an older system of allocating organs for adults and adolescents 12 and older on a first-come first-serve basis with one based on age, geography, blood type, waiting time if necessary, and a Lung Allocation Score (LAS) reflecting survival probability over the next year without a transplant and the likelihood of survival after transplant.  The impact of that change continues: the 2014 (most recent) Annual Report of the OPTN and SRTR shows a continued increase in additions to the lung waitlist with a concomitant increase in removal from the waitlist for transplantation. The median time to transplant was 3.7 months in 2014, and the candidates are sicker, with the LAS now up to 44.4 (range of 0 to 100). The LAS modification in 2005 stimulated growth in transplant rates for patients with restrictive lung diseases (primarily “IPF” or idiopathic pulmonary fibrosis). Patients in this group now represent 50% of all lung transplants. A major revision of the LAS calculation was approved in February of 2015. These changes centered on the variables used for the calculation, and the weighting given to those data elements. In part, these changes were made in an attempt to correct what appears to some to have been an over-enhanced benefit for those with restrictive lung disease. The new scoring should improve the opportunity for patients with pulmonary vascular disease. Future reports will be released to assess the scale and nature of the effects of this change.

As mentioned above, the LAS takes into consideration severity of illness as manifested by the probability of survival prior to lung transplant and the probability of survival following a lung transplant. The algorithm gives each patient a numeric score that balances these two measures of survivability.  Waiting time does not affect wait list priority for adolescents (12 – 17 years old) and adults (>= 18 years old) except under certain circumstances by appeal to the Regional Organ Procurement Organization.  

Children under the age of 12 are not affected by this policy and offered lungs by Priority 1 and Priority 2 status according to urgency as defined below. However, as a result of a highly publicized case in the spring of 2013, UNOS was asked by the Secretary of HHS to develop a method to “make more [lung] transplants available to children…” As a result of this order, in early December of 2015, the OPTN/UNOS Board approved changes that provides broader geographic sharing of lungs from donors under age 18 first to candidates newborn to age 11, then to adolescents age 12 – 17. Requests for consideration go to a newly-constituted National Lung Review Board. Lungs not accepted from these donors then go to adults. The new allocation scheme allows candidates under 2 years old to receive donor organs of any blood type since until about two years infant immune systems are unresponsive to foreign blood types.

2. Ex Vivo Lung Perfusion: [2]

The transplant community is continually looking for ways to expand the donor pool. Specifically, within lung transplantation, a new method under investigation uses mechanically-driven perfusion and ventilation of procured lungs and is called ex vivo lung perfusion (EVLP). This system pumps warm fluid through the lung vessels and ventilates the lung outside the body in a controlled environment. Lungs which may have been discarded in the past can now potentially be considered for use because of the conditioning of suboptimal pulmonary function occurring while on this system. Donor lungs are selected to be considered for EVLP using these indications for EVLP. This holds for both brain death donors (DD) and donors after cardiac death (DCD):


        • Best PaO2/FiO2 <300 mmHg
        • Signs of pulmonary edema either on chest X-ray or physical examination
           at the donor site
        • Poor lung compliance during examination at procurement operation
        • High-risk history, such as >10 units of blood transfusion or questionable
           history of aspiration
        • DCDs with >60 min interval from withdrawal life support to cardiac arrest
           interval

EVLP is one way to increase organ usage leading to a higher transplant rate. Currently, the system is used by a limited number of centers under a clinical trial. However, UNOS is considering incentives for use of the system once preliminary data is confirmed, and based on the positive results the next step will be to seek CMS certification and FDA approval. This technology could have a major effect on lung transplantation since currently only 1 in 5 lung offers are accepted for recipients by transplant programs

The following patient selection criteria are commonly encountered in lung programs. Here they are listed by age group:


Candidates Age 0 – 11 [3]

Priority 1: Candidates with one or more of the following criteria:

 

  • Respiratory failure, defined as having at least one of the following:
    • Requiring continuous mechanical ventilation;  
    • Requiring supplemental oxygen delivered by any means to achieve FiO2 greater than 50% in order to maintain oxygen saturation levels greater than 90%;
    • Having an arterial or capillary PCO2 greater than 50 mmHg,
    • Having venous PCO2 greater than 56mmHg.
  • Pulmonary hypertension, defined as having at least one of the following:
    • Pulmonary vein stenosis involving 3 or more vessels;
    • Any of the following, in spite of medical therapy:
      • cardiac index less than 2 L/min/M2,
      • syncope,
      • hemoptysis
      • suprasystemic PA pressure on cardiac catheterization or by echocardiogram estimate
         

Priority 2:  Candidates who do not any of the criteria for Priority 1.

Candidates age 12 and older [4]
 
The following three issues are taken into consideration when determining the patient’s LAS:


        • “Waitlist urgency measure (expected number of days lived without
           a transplant during an additional year on the waitlist)”
        • “Post-transplant survival measure (expected number of days lived
           during the first year post-transplant)”
        • “Transplant benefit measure (post-transplant survival measure minus
           waitlist urgency measure)”
        • Raw Allocation Score (the difference between the benefit measure and
           the waitlist urgency measure

Factors Used to Predict Risk of Death on the Lung Transplant Waitlist: [5]
        • Forced vital capacity (FVC)
        • Pulmonary artery (PA) systolic (Groups A, C, and D)
        • O2 required at rest (Groups A, C, and D)
        • Age
        • Body mass index (BMI)
        • Diabetes
        • Functional status
        • Six-minute walk distance
        • Continuous mechanical ventilation
        • Diagnosis
        • PCO2
        • Bilirubin (current bilirubin – all Groups; change in bilirubin – Group B)


Factors That Predict Survival After Lung Transplant:
        • FVC (Groups B and D)
        • PCW pressure >= 20 (Group D)
        • Continuous mechanical ventilation
        • Age
        • Serum Creatinine
        • Functional Status
        • Diagnosis

“The calculations define the difference between transplant benefit and waitlist urgency: Raw Allocation Score = Transplant Benefit Measure – Waitlist Urgency Measure.”

The LAS is a dynamic score and is based on the latest clinical information available to UNOS. Each transplant center continuously enters all pertinent data into UNet (the UNOS online data entry system) after each evaluation while on the waitlist.  The patient’s LAS is automatically recalculated based on the latest data entered into UNet.  If there is no data for a patient in UNet, the LAS is 0.  If there are missing bits of data, UNet will automatically assign predetermined default values for the missing data.

To view the entire allocation policy (OPTN Policy #10) with sample calculations, go to: OPTN

The most up-to-date LAS calculator can be found here.




1 Organ Procurement and Transplantation Network (OPTN) Policies. Policy 10.4. “Allocation of Lungs”. 10 November 2016.
2 Machuca TN, Cypel M. “Ex vivo lung perfusion.” Journal of Thoracic Disease, vol 6, no. 8, p. 1054-1062, 1 July 2014.
3 Ibid Paragraph 10.4.E

4 Ibid Paragraph 10.4.D

5 UNOS Heart/Lung News, Jan 19, 2014