For a study, the researchers sought to examine whether NP antibodies affected coagulation and correlated APAs with anti-dsDNA IgG and coagulation markers in nasal polyp (NP) tissue with tissue from control and CRS without nasal polyp (CRSsNP) patients. ELISA was used to test for APA IgG, anti-dsDNA IgG, and the thrombin-anti-thrombin (TaT) complex in patient samples. Antibodies from a subset of specimens were evaluated for modified activated partial thromboplastin time (aPTT) measured using an optical-mechanical coagulometer. Anti-cardiolipin IgG levels in NP were 5 times greater than in control tissue (P<.0001). At 400 µg/mL (36.7 s vs 33.8 s, P=.00024) and 600 µg/mL (40.9 s vs 34.7 s, P=.0037), NP antibodies prolonged aPTT compared with control tissue antibodies. Anti-PE IgG antibodies were substantially greater in NP (P=.027), whereas anti-B2GP IgG was not (P=.084). All APAs were associated with elevated anti-dsDNA IgG levels (R=.77,.71, and.54 for anti-cardiolipin, anti-PE, and anti-B2GP, respectively; all P=.001), but only anti-cardiolipin (R=.50, P=.0185) and anti-PE (R=0.45, P=.037) were associated with TaT complex levels APA In NP, IgG antibodies were higher, and they were linked with autoreactive tissue antibodies. The anticoagulant activity of NP antibodies in vitro was comparable to that determine in anti-phospholipid syndrome, implying that they might have pro-coagulant effects in polyp tissue.