Vitamin K antagonists (VKA) are the most widely used anticoagulants for the prevention
of thrombotic events. Several renal adverse effects have been associated with the
use of VKA. The main aim of our study was to explore the association between international
normalized ratio (INR) levels and microscopic hematuria in patients with VKA.
We performed a cross-sectional study of patients treated with VKA that attended the
outpatient clinic for routine INR control. A simple urinalysis was performed on the
day of the INR control and the precise number of red cells in the urine sediment was
quantified. Demographic data, kidney function tests, comorbidities, anticoagulant
dose and concomitant treatment were registered.
A total of 337 patients were included with median INR levels of 2.6 (IQR 2.1–3.3).
11.9% of the patients presented microscopic hematuria (≥14 RBCs/µl). There was a significant
correlation between INR levels and the number of red blood cells in the urine sediment
(r = 0.201, p = 0.024). In the univariate analysis, microscopic hematuria was associated with having
an INR >3.5 (19% vs. 10.2%, p = 0.046), bacteriuria (15.2% vs. 3.6%, p = 0.015), leukocyturia (14.8% vs. 6.6%, p = 0.026), hypertension (16.2% vs. 9.5%, p = 0.053), and the use of renin-angiotensin system (RAS) blockers (6.9% vs. 17.2%,
p = 0.004). Multivariate logistic regression showed an association between microscopic
hematuria and RAS blockade (OR 0.38, CI 95% 0.163-0.886, p = 0.025), independent from INR levels, hypertension, leukocyturia or bacteriuria.
INR overdose was significantly associated with the presence of microscopic hematuria.
RAS blockade is an independent protective factor for the presence of microscopic hematuria
in anticoagulated patients.