Background Impaired renal function is common in patients with ankylosing spondylitis (AS) and patients also have an increased risk of cardiovascular disease (CVD). Previous studies showed that biologicals, such as anti-Tumour Necrosis Factor (anti-TNF) reduce CVD in patients with inflammatory rheumatic disease. Impaired renal function is a known predictor of CVD (also elevated in AS). We postulated that the favourable cardiovascular effect of anti-TNF might be mediated by improving renal function. However, data about the effect of biologicals on renal function in patients with AS are lacking.

Objectives To assess the effect of anti-TNF on renal function in patients with AS.

Methods Biological-naïve consecutive AS patients treated with etanercept or adalimumab were prospectively followed from 2005 to 2014. Renal function was determined by calculation of the estimated Glomerular Filtration Rate (eGFR), which was estimated with the abbreviated Modification of Diet in Renal Disease (MDRD) formula. Patients were divided into two groups: patients with normal renal function at baseline and patients with impaired renal function at baseline, to investigate whether the effect is different for these groups. Normal renal function was defined by eGFR ≥90 mL/min/1.73 m² at baseline and impaired renal function was defined by eGFR <90 mL/min/1.73 m² at baseline. The effect of anti-TNF on eGFR was analysed using mixed model analysis.

Results 211 AS patients were followed for a median of 156 (36 – 286) weeks. 153 patients had normal renal function and 58 had impaired renal function at baseline. In patients with normal renal function at baseline eGFR decreased significantly over time (β=−0.041, p=0.001), although this association did not remain significant after adjustment for disease activity (β=−0.015, p=0.212). Patients with impaired renal function at baseline did not have a significant change in eGFR over time (β=0.022, p=0.087) and this association remained not significant after adjustment for alcohol consumption, BMI, disease duration and disease activity (β=0.008, p=0.593). The change in eGFR on average over time after starting anti-TNF in AS patients with normal and impaired kidney function are presented in figure 1.

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Abstract AB0837 – Figure 1

Conclusions This study demonstrates that anti-TNF is not associated with renal function in AS patients, which means that use of anti-TNF is safe concerning renal function in patients with AS. From our results it seems that the effect of anti-TNF on CVD in AS patients is not mediated by an effect on renal function.

Disclosure of Interest None declared