Warfarin, INT and PTT

Q: Warfarin can increase? - select one

A) PT/INR

B) аРTТ 

C) PT/INR and aPTT

Answer: C

Although many a times, clinically insignificant, wаrfаriո has a weak effect on most аРTТ reagents. Supratherapeutic warfarin may increase the аРТT noticeably - and can be a warning sign of impending bleeding (see reference #2). This is also because wаrfаriո increases the sensitivity of the аРТΤ to the heраrin effect.

#hematology

#laboratory-medicine

References:

1. Price EA, Jin J, Nguyen HM, et al. Discordant aPTT and anti-Xa values and outcomes in hospitalized patients treated with intravenous unfractionated heparin. Ann Pharmacother 2013; 47:151.

2. Bell DF, Harris WH, Kuter DJ, Wessinger SJ. Elevated partial thromboplastin time as an indicator of hemorrhagic risk in postoperative patients on warfarin prophylaxis. J Arthroplasty. 1988;3(2):181-4. doi: 10.1016/s0883-5403(88)80084-6. PMID: 3397749.