Background High resistance index (HRI), evaluated on the basis of Doppler spectrum of popliteal arteries, enables detection of subclinical changes in small vessels in systemic lupus erythematosus (SLE) patients.

Objective To evaluate the association between decreased values of HRI in SLE patients and selected immunological parameters, the presence of markers of inflammation and classical risk factors for atherosclerosis and also selected clinical manifestations.

Methods The investigation was performed in 76 patients with SLE (age 20-73 years). The mean course of the disease was 8.7 years. The coexistence of APS was confirmed in 17 patients (22.4%). The control group consisted of 30 healthy people.

All the duplex Doppler examinations of popliteal arteries were performed with HDI 3500 (ATL) using 5- 12 MHz linear transducer under standardised conditions.

We evaluated the presence of anti-endothelial antibodies (AECA) and profiles of anti-nuclear antibodies, anti-phospholipid antibodies (aPL) and anti-neutrophil cytoplasmic antibodies. We also analysed markers of inflammation (C-reactive protein, erythrocyte sedimentation rate and fibrinogen), classical risk factors for atherosclerosis (hypertension, hyperglycaemia, hyperlipidaemia, smoking and positive family history for cardiovascular disease) and clinical complications including cardiovascular and central nervous system manifestations, lupus nephritis, thromboembolic disorders and vasculitis.

Statistical analysis was performed with chi²Yates, chi²Pearson, rank Spearman correlations tests. Logistic regression analysis and multivariate stepwise analysis were also done. All statistical analyses were performed with STATA 11.

Results We found that HRI values in patients with SLE were significantly lower in comparison with the control group (p< 0.0001). We also showed that the coexistence of APS significantly increased risk of lower values of HRI presence (OR = 11.40; 95% CI:1.69-77.03), and from among aPL the most significant were aCL IgG (OR = 7.43; 95% CI:1.82-30.36), aCL IgM (OR = 7.83; 95% CI:1.08-56.53) and anti- β2-GPI antibodies (OR = 5.76; 95% CI:1.17-28.26). Other serological markers, which significantly influenced decreased values of HRI were AECA (OR = 14.84; 95% CI:2.76-79.66). Furthermore, we found significant negative correlation between HRI values and the presence of thromboembolic disorders (R = -0.25; p = 0.0299) and the duration of SLE (R = -0.23; p = 0.0427).

We have found no associations between decreased HRI values and the rest of analysed variables.

Conclusions 1. HRI values are significantly decreased in SLE patients. 2. The coexistence of APS and the presence of aPL and AECA are risk factors for decreased HRI values in SLE patients. 3. There is a significant reverse relationship between HRI values and the duration of the disease and the presence of thromboembolic changes in SLE patients.