Un dosage de tryptase sérique dans des situations d’urgence est-il utile ?

Abstract

Serum tryptase is a specific indicator of systemic allergic reactions. The aim of the present study was to evaluate the value of serum tryptase determinations in diagnosing anaphylactoid reactions and sudden deaths in an emergency room. Tryptase concentrations were determined using the Pharmacia UniCap-Tryptase fluoro-immuno-assay in 21 patients referred to the emergency room of our hospital. A diagnosis of anaphylaxis was established by an allergologist based on clinical criteria. The tryptase level was increased in 5 out of 8 patients in anaphylactic shock. In the 3 other patients, the level was within normal limits (false negative), probably because of the delay in obtaining the blood sample from them. In 5 cases of non-anaphylactic sudden death, the tryptase level was within normal limits; in 1 other case, a false positive result was due to attempted cardiac resuscitation. This study confirms previous observations that serum tryptase is not increased in cases of non-anaphylactic sudden cardiac or respiratory arrest, except in those cases where thoracic compression precedes the venipuncture. Thus, determination of the serum tryptase level should be useful in cases of unexplained sudden death. Nevertheless, a normal serum tryptase level does not exclude a diagnosis of anaphylaxis, given the possibility of false negative results. To avoid this, it is essential that the blood sample for this assay should be obtained within 2 h of the onset of anaphylaxis.