Prevalence of Subclinical Amyloidosis in a Cross-sectional Study of Egyptian RA Patients without Proteinuria

BACKGROUND: Amyloidosis is a life-threatening complication of Rheumatoid Arthritis (RA) that should be detected as early as possible to avoid its morbidity and mortality. OBJECTIVE: To detect subclinical amyloidosis in RA patients without proteinuria and a disease duration more than 5 years. PATIENTS: Eighty-six RA patients seen between October 2013 and August 2014 were recruited for the study. Those with 5 years disease duration were included in the study but those who had proteinuria, serum creatinine > 1.5 mg/dl, disease onset before the age of 16 years or improper specimens, were excluded, leaving 30 eligible patients (23 women, 7 men). The clinical, laboratory and imaging results and treatments were maintained for each patient. Abdominal Fat Aspiration Biopsy (AFAB) was performed on all 30 patients. Amyloid deposits were spotted by polarised light microscopy following Congo red staining. Informed consent was acquired from all patients. Clinical disease activity was scored according to DAS. ELISA measured serum amyloid A protein (SAA), CRP and RF. RESULTS: AFAB stained positive for amyloid in 4 (13.3%) patients out of 30. The amyloid deposits were (1+) in 1 patient and (2+) in 3 patients. Longer RA duration correlated positively with amyloidosis (12.50 years versus 6.15years) (P < 0.001). Extra-articular manifestations were present in 50% of the amyloid patients and in 15.3% of the non-amyloid patients. This difference was significant (P < 0.01). DAS 28 score was higher in amyloid patients (P < 0.001). No difference was found between amyloid and non-amyloid patients regarding age, sex or deformities. SAA was significantly higher in amyloid patients (P < 0.001). However, haemoglobin levels were found to be significantly lower in amyloid patients (P < 0.001). CONCLUSION: The prevalence of subclinical amyloidosis by AFAB was found to be (13.3%). The use of AFAB should be encouraged, particularly in patients with longer disease duration and low haemoglobin level to confirm early detection of subclinical amyloidosis.