I thank Dres. Alnaes and Helnes Bergen for their stimulating comment on
my medical algorithm on the Diagnosis and Treatment of Radiocontrast
Media Hypersensitivity.1 In their comment, they raised
attention to the possible addition of desensitization to radiocontrast
media (RCM) management, which was not depicted in the
algorithm.2 I have been well aware of several reports
on desensitization and have already discussed them in a previous paper,
however commented there that “successful desensitization of RCM has
been reported for immediate hypersensitivity reactions to RCM, but it is
only used anectodically” and concluded not to include this procedure
into the algorithm.3
In addition to the two papers on desensitization to RCM cited by Dr.
Alaes, also a handful other cases have been published, some of them
older. To my knowledge, at least as far as I can access these case
reports, in none of these patients a proper allergy diagnosis and
management has been performed and in most, if not all of these patients,
desensitization probably was unnecessary. In the described cases, skin
testing has not been performed or was even negative indicating a higher
probability for a non-allergic immediate hypersensitivity reaction
(IHR), in the history before desensitization was performed in several
cases the RCM was not changed, but the same not tolerated RCM was given
again and radiologists in vain relied on premedication to prevent
recurrent attacks, and no skin test-negative RCM was identified and
used. None of the cases published convinced me of the need for
desensitization. Performing the examination with a skin test-negative
RCM would with a high probability be successful.4 I
would expect the success of desensitization was rather due to changing
to a different isoosmolar RCM (and probably not to adding premedication)
than the desensitization procedure itself, as alone changing the
implicated RCM to another one in one study reduced the risk of recurrent
IHR by 67.1% (odds ratio: 0.329; P = 0.001), whereas steroid
premedication did not show protective effects.5
Our group of European Network on Drug Allergy experts have highlighted
that rapid desensitization is a procedure that can be used to provide a
temporary tolerance to a first-line drug when no alternative is
available.6 This implies for RCM hypersensitivity that
using a skin-test-negative RCM for the next examination as an
alternative drug is next step and not immediate desensitization. One
problem with desensitization is that too many doctors employ it
uncritically and without prior proper allergy workup, best with drug
provocation test. The high rate of successful desensitizations without
prior confirmation of drug hypersensitivity in the literature is in part
explained by the fact that many of those patients would not have reacted
anyway. I have yet to find convincing evidence to add desensitization as
a standard therapeutic option to the RCM management algorithm.
Having said this, I am eagerly following up the literature on RCM
desensitization with great interest to be prepared, should I encounter
an own patient, who would react severely to an alternative skin
test-negative RCM after following the algorithm. Until now, colleagues
and I have not met such a patient, however, I would seriously consider
desensitization as an option in such a situation. Thus, I thank Dres.
Alnaes and Helsen Bergen for bringing up that interesting topic for
discussion.