A Revision of the 1990 Working Formulation
for the Classification of Pulmonary Allograft Rejection:
Lung Rejection Study Group (LRSG)
In 1990, the International Society for Heart and Lung
Transplantation sponsored a workshop to develop guidelines for the standardization
of nomenclature in the histologic diagnosis of lung rejection.1 At this meeting, a
core group of pathologists developed a grading scheme for lung allograft rejection
which could be used to compare data from independent institutions. The intention
was to develop a simple, easily taught, and readily reproducible grading system
that incorporated the advantages and benefits of the multiple grading systems
utilized at that time. The working formulation was readily adopted at most
institutions performing lung transplantation in 1990, and over the ensuing five
years, it was accepted de novo by most new lung transplant programs. For the most
part, it has been perceived as an excellent classification and grading formula. In
order to respond to new developments in the field and an increasing wealth of
experience by a greater number of pathologists, a second meeting of the LRSG was
held at the University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
in March 1995. The purpose of this meeting was to critically assess the merits of
the initial working formulation and, based on published data and to a lesser
extent, experience collected at multiple transplantation centers, improve the
initial working formulation. The goal was to maintain scientific and biologic
accuracy while striving to streamline the classification into one that would be
pathologically, clinically and therapeutically relevant. The revised
classification was designed so that it was based on histologic findings of acute
and chronic lung rejection primarily utilizing transbronchial biopsy as the means
of allograft monitoring in both adults and children.2-8 While the importance of a
morphology based system for the interpretation of pathologic abnormalities was
emphasized, it was noted that all biopsy data needed to be interpreted in an
integrated clinical context to allow optimum patient management and clinical
decisions.9 It was also noted that infection and rejection often occur together
and can be confused histologically.10,11 For this reason, exclusion of infection
was felt to be essential for accurate and reproducible interpretation of allograft
biopsies.
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