A SIMPLE SCREENING-TEST FOR VARIANT TRANSTHYRETINS ASSOCIATED WITH FAMILIAL TRANSTHYRETIN AMYLOIDOSIS USING ISOELECTRIC-FOCUSING

Variant forms of the plasma protein transthyretin (TTR) are associated with the most frequently occurring type of familial systemic amyloido sis. Organ system involvement in transthyretin type amyloidosis (ATTR) is often similar to that which occurs in light chain amyloid disease (AL). The proper diagnosis of ATTR is important since treatment (liver transplantation) differs from that in AL (chemotherapy). We present a two-step test to screen sera for variant TTRs using non-denaturing ge l electrophoresis performed in 7.5% acrylamide (PAGE) followed by isoe lectric focusing (IEF) between pH 3.0 and 7.0 in 2.5 M urea. Serum sam ples from 110 patients with amyloidosis and their relatives were teste d using this IEF technique and compared to genetic mutation results. S era from patients with ATTR who underwent liver transplantation were a lso examined prior to and following surgery. IEF analysis showed the p resence of both wild-type and variant TTR in 74 of the 110 serum sampl es tested. Genomic DNA from peripheral blood was used to identify TTR gene mutations in 77 of the 110 patients. Fifteen variants including V al(122)Ile, preponderant in the African-American population, could be demonstrated by IEF. The sensitivity of IEF was 96% (74/77) and the sp ecificity was 100% (33/33). The predictive values for a positive or ne gative result were 100% (74/74) and 92% (33/36), respectively. There w ere no false-positive results and 4% (3/77) false-negative results. In sera from patients with ATTR who underwent liver transplantation, var iant TTR was detected by IEF before, but not after, surgery. A simple, accurate, sensitive method is presented as a useful screening test fo r variant transthyretins associated with ATTR. (C) 1998 Elsevier Scien ce B.V. All rights reserved.