We read with great interest the study by Alvarez et al. on gender mismatched lung transplantation (LTx) and clinical outcomes [1]. We agree with the authors' conclusion that donor-recipient gender mismatch does not have a negative impact on early graft function and mortality following LTx. However, we would like to use this comment to expand on the rationale.
Gender is a major determinant of lung size, together with height (age and race) [2]. Lung size can be estimated by the predicted total lung capacity (pTLC). Alvarez et al. describe that at their institution, the size matching decision is among other factors based on the pTLC of the donor, as compared to pTLC of the recipient. Specifically, variations in pTLC of up to 20% between donor and recipient were accepted.
In the USA, candidates for LTx are listed for acceptable donor height ranges. As an example, a 30-year old, 170-cm male candidate (with a pTLC of 6.27 l, as per the equation used by Alvarez et al.) could be listed for an acceptable height range from 160 to 180 cm. If the donor were a 30-year old, 160 cm tall female (with a pTLC of 4.93), the resulting donor to recipient pTLC-ratio would be 0.78. A pTLC-ratio <0.8 has been reported to be associated with worse survival after LTx [3]. When we reviewed the United Network for Organ Sharing (UNOS) Standard Transplant Analysis and Research (STAR) data of the thoracic organ transplant registry, we confirmed the association of a pTLC-ratio <0.8 with decreased survival [4]. In the pTLC-ratio <0.8 group, 87% of patients had a female donor to male recipient gender-mismatch. More importantly, when lung size mismatch (via the pTLC-ratio) was accounted for, gender mismatch was not independently associated with survival [4, 5].
We wholeheartedly agree with the approach to use donor and recipient pTLC for the size matching decisions. Utilizing pTLC will account for the gender effect on lung size. A pTLC-based approach could make apparent the possible increased risk associated with significant undersizing that can occur in a height-based allocation system, when a female donor to male recipient mismatch occurs.
Conflict of interest: none declared.
References
- 1.Alvarez A, Moreno P, Illana J, Espinosa D, Baamonde C, Arango E, et al. Influence of donor-recipient gender mismatch on graft function and survival following lung transplantation. Interact CardioVasc Thorac Surg 2013;16:426–6 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Egan TM. Size matters: it's all about height, sex and race! ISHLT- Links [published July 2012, accessed Jan 2013]. Available from: http://www.ishlt.org/ContentDocuments/2012JulLinks_Spotlight.html . [Google Scholar]
- 3.Sweet SC. Pediatric living donor lobar lung transplantation. Pediatr Transplant 2006;10:861–8 [DOI] [PubMed] [Google Scholar]
- 4.Eberlein M, Arnaoutakis GJ, Yarmus L, Feller-Kopman D, Dezube R, Chahla MF, et al. A higher predicted total lung capacity (pTLC) ratio (pTLC donor/pTLC recipient) is associated with improved survival after lung transplantation. J Heart Lung Transplant 2011;30suppl 1:S127 [Google Scholar]
- 5.Eberlein M, Reed RM, Permutt S, Chahla MF, Bolukbas S, Nathan SD, et al. Parameters of donor-recipient size mismatch and survival after bilateral lung transplantation. J Heart Lung Transplant 2012;31:1207–1213 [DOI] [PubMed] [Google Scholar]