Detection of AA-type amyloid protein in labial salivary glands

ABSTRACT

Objectives: Among the diverse forms of amyloidosis, secondary type is the most frequent one. Diagnosis of amyloiddeposition is based on the identification of the fibrillary protein amyloid by means of Congo Red (CR) or crystalviolet (CV) stains, but these techniques do not differentiate between the different types of amyloid fibrils. Theaim of this study was to identify by immunofluorescence (IF) AA amyloid a pathological fibrillar low-molecularweightprotein formed by cleavage of serum amyloid A (SAA) protein in labial salivary gland (LSG) biopsies frompatients with secondary amyloidosis.Study design: 98 LSG were studied, 65 were from patients with secondary amyloidosis and 33 from subjects withchronic inflammatory diseases without evidence of this anomaly. All sections were stained with hematoxylin andeosin (H&E), CV, CR and IF using anti-AA antibodies. Positive and negative controls were used for all techniques.Results: CV and CR demonstrated that the amyloid substance was found mainly distributed periductally (93.8%),followed by periacinar and perivascular locations (p<0.001); however, the IF demonstrated that amyloid AA substancepredominates in the periacinar area (73.8%), followed by periductal and perivascular locations (p<0.001).IF has a sensitivity of 83%, 100% of specificity, 100% of predictive positive value and 75% of predictive negativevalue.Conclusions: The results of this study confirm the efficacy of the LSG biopsy as a highly reliable method fordiagnosis of secondary amyloidosis (AU)