Relationship between Modified Body Mass Index and Prognosis of Renal Amyloid a Amyloidosis

Overhydration occurs in nephrotic syndrome related to kidney involvement of amyloid A (AA) amyloidosis, which can cause an overestimation of body mass index (BMI). Modified BMI (mBMI, albumin×BMI) may be a better marker of nutritional status; therefore, we investigated the relationship between mBMI and the prognosis of patients with renal AA amyloidosis.

We retrospectively reviewed the data of patients with biopsy-proven renal AA amyloidosis who were followed up between January 2001 and May 2013. Data regarding baseline characteristics, etiology of amyloidosis, dialysis, and mortality were recorded. Patients were divided into two groups according to median mBMI (group 1, n=60 and group 2, n=61).

The median age and follow-up period of the cohort (M/F 37/84) were 43 (19) years and 26 (56) months, respectively. Familial Mediterranean fever (37.2%) and tuberculosis (24.8%) were the most common etiologies. The baseline serum creatinine and albumin and proteinuria levels were 1.3 (2.2) mg/dL, 2.6 (1.5) g/dL, and 5.3 (7) g/day, respectively. The mBMIs of groups 1 and 2 were significantly different [41.5 (15.6) vs. 74.2 (21.8) g.kg/m², p =< 0.001]. Group 1 patients had shorter time to dialysis (13.9±20.8 vs. 25.7±28.1 months, p=0.040) and higher mortality (50% vs. 32.7%, p=0.041), whereas the rates of dialysis inception were similar. The area under the curve for mBMI as a predictor of mortality was larger than that for serum albumin and BMI in ROC analysis.

Lower mBMI has been associated with worse prognosis in renal AA amyloidosis. As an anthropometric measure of nutritional status, mBMI may be a better marker in patients with hypoalbuminemia.