Shortened Activated Partial Thromboplastin Time May Help in Diagnosing Hereditary and Acquired Angioedema.

OBJECTIVE To evaluate whether activated partial thromboplastin time (APTT) could be used in the laboratory diagnosis of hereditary or acquired angioedema (HAE or AAE) with and without C1 inhibitor (C1-INH) deficiency. METHODS In a prospective investigation, APTT and other coagulation parameters were determined in 149 adult patients with various types of angioedema and in 26 healthy participants (HP). RESULTS Mean APTT was significantly shortened in HAE-C1-INH type I (p < 0.0001) and type II (p = 0.0017) and in AAE-C1-INH (p < 0.0001) compared to the HP. APTT was shortened under the reference range (26-36 s) in 33/45 (73.3%) patients with HAE-C1-INH, 10/15 (66.7%) patients with AAE-C1-INH, 4/27 (14.8%) patients with HAE with normal C1-INH, 1/32 (3.1%) patients with histaminergic angioedema, 4/30 (13.3%) patients with nonhistaminergic angioedema and in 2/26 (7.7%) HP. Thus, a shortened APTT was obtained in 8-9 times more patients with angioedema due to C1-INH deficiency when compared to patients with various forms of angioedema with normal C1-INH and also to HP. CONCLUSIONS A shortened APTT may help to diagnose HAE-C1-INH and AAE-C1-INH when determination of C1-INH is not yet available.