Serum amyloid A as a marker of disease activity and treatment response in Takayasu arteritis.

Assessment of disease activity in Takayasu arteritis (TA) is challenging. We aimed to study utility of serum amyloid A (SAA) to assess disease activity and its association with SAA gene polymorphisms, if any, in our TA patients. Serum of 99 consecutive adult TA patients and 40 healthy controls were assayed for SAA. Depending on the ITAS2010 and ITAS-CRP score, patients were designated as having active disease if ITAS2010 ≥ 2 or ITAS-CRP ≥ 3 and stable disease if ITAS2010 = 0 or ITAS-CRP is ≤1. Clinical ITAS of 0 with raised inflammatory markers scoring a ITAS-CRP of 2 was considered as indeterminate for disease activity assessment. Repeat SAA levels for active group was measured after 6 months from baseline. SAA levels between active and stable disease as well as serial levels were compared. DNA of 40 patients and controls were genotyped for SAA polymorphisms (rs12218, rs2468844) and the allele frequencies were compared. At baseline, SAA levels were higher in patients as compared to controls (137.4 vs 100.8 ng/ml, p = 0.001) and higher in patients with active disease (166.4 ng/ml) than those with stable disease (98.2 ng/ml), p = 0.001. SAA decreased during follow-up in treatment responders (189.9 ng/ml at baseline vs 119.0 ng/ml at follow-up, p = 0.008); in contrast, there was no significant change among non-responders during follow-up. Allelic frequencies of SAA gene polymorphisms did not differ between cases and controls. SAA may be a reliable biomarker to assess disease activity and treatment response in TA.