Blood return on aspiration before immunotherapy injection.

accordingly, his clinic has ‘‘ceased the policy of aspiration before injection.’’ Although respecting this position, I am not completely in agreement with it. The data presented by Waibel certainly confirm the common knowledge that strict conformity to official recommendations, eventually in combination with additional safety measures like the use of smaller needles, can reduce to extremely low levels the risk of accidental intravasal injection, but the possibility of this undesired event cannot be absolutely ruled out. During my 7 years (first as a medical student and then as a resident) in the allergy unit of a university hospital, I remember 2 cases when intravasal injection was avoided because of syringe aspiration: in one case the operator was a young resident, and in the other the operator was an experienced allergologist. Beyond their anecdotal value, these episodes show that accidental intravasal injection during subcutaneous administration of immunotherapy is a very rare but not impossible event. The lack of literature data supporting the usefulness of syringe aspiration before injection is probably due to a publication bias: it is unlikely that an operator reports an adverse event happened when a safety recommendation, although based on expert opinion only, was not followed, and on the other hand, a report of a possible adverse event avoided by means of a common safety practice would have virtually no chance for publication. The interindividual variability of the anatomic features, together with the impossibility to visualize the deep vascular network, can be the cause of accidental intravascular injection, even for an experienced operator strictly following recommended injection protocols. The risk is increased for younger, less experienced, and/or learning health care personnel. Syringe aspiration before injection is currently the only technique that can show whether a blood vessel has been accidentally punctured. Moreover, it is easy to learn, to perform, and to interpret; it is rapid and optimally tolerated by patients; and it has no side effects and no cost. Taking into consideration these positive features and the possible severe adverse effects (up to rapid and fatal anaphylaxis) of the intravascular injection of immunotherapy, my humble opinion is that syringe aspiration should be always performed before subcutaneous injection, as recommenBlood return on aspiration before immunotherapy injection