Abstracts S245as a suitable indicator for size matching. The ISHLT consensus report defines an acceptable size range as a pTLC ratio of 75% to 125%. However, there are no definitive guidelines on size matching for specific underly-ing diseases such as pulmonary fibrosis. Focus was placed on single lung transplantation, as size matching may be of even greater importance. As only limited studies of lung size matching in this patient cohort have been published, we aimed to analyze the correlation between pTLC ratio and overall survival.Methods: We reviewed all patients who received a single lung transplant for pulmonary fibrosis at our institution between 1999 and 2017. We calculated the donor to recipient pTLC ratio and defined two groups: “undersized” and “oversized” (pTLC ratio < 100% and ≥ 100%, respectively). We compared overall survival using the Kaplan-Meier analysis with a log-rank test.Results: We included 98 patients in our analysis. Mean recipient pTLC was 6.26±1.05L and mean donor pTLC was 6.09±1.10L. Mean donor to recipient pTLC ratio was 98.01±11.71%. 51 patients were included in the “under-sized” group and 47 patients in the “oversized” group (mean pTLC ratio 89.50±8.36L and 107.23±6.78L, respectively). Median survival time was 2.95 years (range, 0.02-15.21 years) in the "undersized" group and 4.67 years (range, 0.01-22.25 years) in the "oversized" group. Kaplan-Meier analysis revealed a correlation between lung sizing and survival, with a trend towards improved survival in patients in the “oversized” group (p= 0.05).Conclusion: We observed improved survival in patients receiving an over-sized lung allograft after single lung transplantation for pulmonary fibrosis. Further analysis will have to clarify the impact of lung sizing on postopera-tive outcomes such as ventilation time, ICU stay and hospital stay in this specific patient cohort.( 607)Using a Computerized Virtual Crossmatch Program for Solid Organ Transplant Donor Selection: Evaluation of VxMatchD. Chen , 1 C. Brack, 2 R. Tian, 1 W. Hanshew. 1 1 Duke University Health System, Durham, NC; 2 HLA Data Systems, Houston, TX.Purpose: For heart and lung transplantation, a prospective crossmatch (XM) may not be possible unless a local donor is available. Our transplant center has used virtual crossmatch (vXM) to select deceased donors for heart and lung transplantations for more than ten years, which has allowed us to accept donors from outside of our organ procurement territory. The vXM was done by manually checking the recipient’s HLA antibody profiles within our HLA lab database against the potential donor’s HLA typing to identify if the recipient has any donor-specific antibodies (DSA) in the most recent serum tested and in historical sera. To ensure no DSA was missed, the vXM was manually done by multiple transplant professionals at different stages for each sensitized recipient when a donor offer was available. We recently deployed computerized virtual crossmatch system VxMatch from laboratory informatics vendor HLA Data Systems. VxMatch integrates HLA datasets to query required data for analysis to perform vXM and post-transplant DSA surveillance. The aim of the validation is to evaluate VxMatch performance.Methods: A total of 56 vXMs performed manually for sensitized recipients were re-analyzed using the new program VxMatch. 35 of the 56 patients have calculated panel reactive antibodies (cPRA) equal to or greater than 80%. VxMatch integrates our lab management database (mTilda) containing donor typings and recipient antibodies and constructs visualizations of reactivity trends, recent and historical DSA.Results: We found a 100% concordance for identification of DSA between vXM and VxMatch. It took less than 5 minutes to complete the VxMatch while the conventional vXM took 30 minutes on average. For each identified unacceptable antigen, the system provides detailed information, including antibody specifici-ties, MFI, serum date and a graph showing the MFI changes of DSA over time. The VxMatch can operate in both technologist’s and supervisory level modes to allows us to review each bead carrying potential unacceptable HLA antigen at alpha chain, beta chain, or allele level. VxMatch can also be used to identify the serum with peak DSA for final XM and track the change of DSA post-transplant.Conclusion: Our validation suggests that this new computerized VxMatch system is a user-friendly, reliable and powerful tool for vXM donor selection and post-transplant DSA management.( 605)Organ Sequence Number (SN) is Not a Proxy for Organ QualityM. Harhay , 1 M.J. Crowther, 2 J.M. Diamond, 1 T. DiSanto, 1 S. Rubin, 1 Z. Penfil, 1 C. Bermudez, 1 J.D. Christie, 1 E. Cantu. 1 1 Hospital of the University of Pennsylvania, Philadelphia, PA; 2 University of Leicester, Leicester, United Kingdom.Purpose: Donor suitability decision making for transplant is complex. Criteria are subjective and can vary significantly within and between trans-plant centers. Position on the match run for organ acceptance, indicated by an organ’s sequence number (SN) is considered a proxy of organ quality but there is no evidence to support the use of the SN in the decision-making process. We sought to determine factors associated with organs with a higher SN and whether SN had any impact on mortality.Methods: Data from the UNOS Starfile and the potential transplant recipient registry ranging from 2007-2014 were examined. Multivisceral, redo and pediatric lung transplants were excluded. Multivariable logistic regression was used to quantify the association between SN and a selected set of fac-tors (center volume, offer timing, bronchoscopy and X-ray results, pulmo-nary infection, cause of death, and p02). Differences in mortality based on the final SN of an accepted organ was examined with a flexible parametric Royston-Parmar model.Results: 204,513 lung offers resulted in 10,898 transplants. 37% of lungs were accepted by the first (24.6%) or second (12.4%) matched recipient, with 69.5% accepted by the 10 th offer. Of the remaining 30.5%, 20.2% were accepted by SN #50, 6.8% between SN #51-100 and 3.5% after SN #100. Higher SN organs used for transplant were significantly associated with abnormal organ quality measures and offers to high volume centers. Pulmonary infection, donor cause of death and timing of offer were not associated with a higher SN. Mortality comparisons through 5-years dem-onstrated no difference with respect to SN (Figure).Conclusion: Of the organs accepted for transplant, almost 70% are accepted by the top ten matched recipients. Abnormalities of organ quality indica-tors result in higher SN before acceptance for transplant. Larger centers more commonly accept organs with higher SN and timing of an offer does not explain this difference. Mortality for higher SN is no different than lower SN.( 606)Size Matters in Single Lung Transplantation for Pulmonary Fibrosis!K.L. Freystaetter , 1 G. Parry, 2 G. Meachery, 2 J.L. Lordan, 2 A.J. Fisher, 2 J. Dark, 1 O. Senbaklavaci. 1 1 Department of Cardiothoracic Surgery, Freeman Hospital, Newcastle Upon Tyne, United Kingdom; 2 Institute of Transplantation, Freeman Hospital, Newcastle Upon Tyne, United Kingdom.Purpose: Donor lung allocation is guided by size matching. Predicted total lung capacity (pTLC) is routinely used, with donor-to-recipient pTLC ratio
