A multicenter study of the clinical, laboratory characteristics, and potential prognostic factors in patients with amyloid A amyloidosis on hemodialysis.

INTRODUCTION: While light chain (AL) amyloidosis is more common in western countries, the most common type of amyloidosis is amyloid A (AA) amyloidosis in Eastern Mediterranean Region, including Turkey. Although worse prognosis has been attributed to the AL amyloidosis, AA amyloidosis can be related to higher mortality under renal replacement therapies. However, there are no sufficient data regarding etiology, clinical presentation, and prognostic factors of AA amyloidosis. The objective of our study is to evaluate the clinical, laboratory characteristics, and possible predictive factors related to mortality in patients with AA amyloidosis undergoing hemodialysis (HD).

METHODS: This multicenter, cross-sectional study was a retrospective analysis of 2100 patients on HD. It was carried out in 14 selected HD centers throughout Turkey. Thirty-two patients with biopsy-proven AA amyloidosis and thirty-two control patients without AA amyloidosis undergoing HD were included between October 2018 and October 2019. There was no significant difference between the groups in terms of age and dialysis vintage. Causes of AA amyloidosis, treatment (colchicine and/or anti-interleukin 1 [IL] treatment), and the number of familial Mediterranean fever (FMF) attacks in the last year in case of FMF, systolic and diastolic blood pressures, biochemical values such as mean CRP, hemoglobin, serum albumin, phosphorus, calcium, PTH, ferritin, transferrin saturation, total cholesterol levels, EPO dose, erythropoietin-stimulating agents resistance index, interdialytic fluid intake, body mass indexes, heparin dosage, UF volume, and Kt/V data in the last year were collected by retrospective review of medical records.

FINDINGS: Prevalence of AA amyloidosis was found to be 1.87% in HD centers. In amyloidosis and control groups, 56% and 53% were male, mean age was 54 ± 11 and 53 ± 11 years, and mean dialysis vintage was 104 ± 94 and 107 ± 95 months, respectively. FMF was the most common cause of AA amyloidosis (59.5%). All FMF patients received colchicine and the mean colchicine dose was 0.70 ± 0.30 mg/day. 26.3% of FMF patients were unresponsive to colchicine and anti-IL-1 treatment was used in these patients. In AA amyloid and control groups, erythropoietin-stimulating agents resistance index were 7.88 ± 3.78 and 5.41 ± 3.06 IU/kg/week/g/dl, respectively (p = 0.008). Additionally, higher CRP values (18.78 ± 18.74 and 10.61 ± 10.47 mg/L, p = 0.037), lower phosphorus (4.68 ± 0.73 vs. 5.25 ± 1.04 mg/dl, p = 0.014), total cholesterol (135 ± 42 vs. 174 ± 39 mg/dl, p < 0.01), and serum albumin (3.67 ± 0.49 mg/dl, 4.03 ± 0.22, p < 0.01) were observed in patients with AA amyloidosis compared to the control group.

DISCUSSION: In this study, we found that long-term prognostic factors including higher inflammation, malnutritional parameters, and higher erythropoietin-stimulating agents resistance index were more frequent in AA amyloidosis patients under HD treatment.