Serum amyloid a and risk of death and end-stage renal disease in diabetic kidney disease

Aims To determine if serum levels of serum amyloid A (SAA) predict death and end-stage renal disease in a cohort of people with diabetic kidney disease. Methods In a longitudinal cohort study of 135 participants with type 2 diabetes and diabetic kidney disease, serum samples were assayed for SAA. Censored time-to-event analyses in Cox-proportional hazard models were utilized to assess SAA as a predictor of the primary outcome of death and end-stage renal disease. Results Participants were 73% Mexican-American (99/135) and 55% men (75/135), with a mean ± SD age of 57 ± 7.5 years. At baseline, participants had hemoglobin A1c of 8.6 ± 2.3%, systolic blood pressure of 153 ± 27 mm Hg, body mass index of 31 ± 9 kg/m², median urine-albumin-to-creatinine ratio of 1861 mg/g (interquartile range 720–3912 mg/g), and estimated glomerular filtration rate of 55.7 ± 22.3 ml/min/1.73 m². Over a median duration of follow-up of 3.5 years, 44% (60/135) of participants experienced a primary outcome event. The hazards ratio for the primary outcome was 3.03 (95% CI 1.43–6.40, p = 0.003) in the highest (> 1.0 μg/ml) compared to the lowest (< 0.55 μg/ml) SAA tertile in a model adjusted for urine-albumin-to-creatinine ratio, estimated glomerular filtration rate, age, sex, and race/ethnicity. Addition of SAA as a covariate improved the model C-statistic (Δ c = 0.017). Conclusions In a longitudinal cohort study of participants with type 2 diabetes and DKD, higher levels of serum SAA predicted higher risk of death and ESRD. SAA is a promising targetable biomarker for DKD.