Untitled - Roche Trasplantes

BIOPSIA DE PROTOCOLO EN EL TRASPLANTE RENAL
A recent analysis of the reproducibility of the reading of arteriolar hyalinosis demonstrates
the problem nicely (14). In this study the authors compared two protocols for reading
–the standard Banff schema and a new schema developed by Mihatsch. The reproducibility
of the new schema was better than the standard Banff schema (kappa statistic 0.67
versus 0.52 comparing 45 biopsies from 38 patients), but the information derived from
the readings was less informative. In the new schema, reproducibility was improved
through reduction of the frequency with which intermediate scoring grades were used.
The number of times when scores of 1 and 2 were used dropped from 64 using Banff to
24 with the new system. This meant that biopsies were scored as 0 or 3 most of the
time, which is little better than a binary decision of present/absent.
The essence of the problem is thus to find the balance between multiple grades of distinction
for a given event such as tubulitis or tubular atrophy, which extracts maximum
amounts of information from the biopsy, and simple grading systems which are highly
reproducible but uninformative. The compromise that is represented by the current Banff
schema, does at least have widespread application across transplant programs and through
many clinical trials. It is important to recognize that it remains limited by the degree of
reproducibility at the margins and could suffer further refinement with benefit. The areas
of contention remain, for example, the relevance of cellular infiltrate in areas of fibrosis.
The current schema requires these to be ignored, but that leads to the potential for variability
in interpretation of exactly what constitutes an area of fibrosis in which the infiltrate
is to be ignored. Fortunately, the schema is under continuous revision and improvement,
so it is reasonable to hold the view that, despite the areas of poor reproducibility, the
Banff schema for the interpretation of renal allograft pathology is the best that we have
available.
DEFINITIONS AND A MODEL OF CAN
Understanding the complexity of the entity of chronic allograft nephropathy (CAN) has
taken many years, since unlike acute rejection, it cannot be easily identified clinically, is
multifactorial in origin and evolves over years and not days or hours. The reliability and
sensitivity of serum creatinine measurement contributed substantially to the ability to
diagnose and treat acute rejection in the early years of transplantation and is still one of
the most reliable tools that we use in the clinic to identify patients in need of further investigation
and change in management during the first few weeks after a renal transplant.
Since the serum creatinine is also a fairly reliable indicator of chronic graft failure,
as demonstrated by studies examining creatinine at one year as a predictor of graft loss,
it has been natural to assume that monitoring the serum creatinine will identify grafts at
risk from chronic graft failure and CAN. Experience has, however, taught us that this strategy
does not, on the whole, allow identification of CAN at a stage when intervention can
substantially alter the course of events. It is central to the understanding of CAN to realise
why this is the case. It is also central to any strategies that might be effective in the
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