Automated enzymatic mitochondrial antibody assay for the diagnosis of primary biliary cirrhosis: applications of a routine diagnostic tool for the detection of antimitochondrial antibodies.
OBJECTIVE
An automated enzymatic mitochondrial antibody assay (EMA) kit for the diagnosis of primary biliary cirrhosis (PBC) has become commercially available recently. The aim of this study was to assess the clinical utility of the enzyme inhibition assay using this EMA kit for the diagnosis of PBC.


METHODS
We tested the immunoreactivity of sera from 54 histologically confirmed Japanese PBC patients to the 2-oxo-acid dehydrogenase complex (2-OADC) enzymes by enzyme inhibition assay using commercially available TRACE (EMA) assay kit, and compared the results with those of indirect immunofluorescence, commercial enzyme-linked immunosorbent assay (ELISA) using MESACUP Mitochondria M2 kit, and immunoblotting on bovine heart mitochondria.


RESULTS
Of the 54 sera, 43 (80%) were positive for antimitochondrial antibodies (AMA) by immunofluorescence, 39 (72%) for enzymatic inhibitory antibody to pyruvate dehydrogenase complex (PDC) by EMA, 33 (61%) for immunoglobulin G (IgG) class anti-PDC antibody by ELISA, and 53 (98%) for IgG, IgM, or IgA class antibodies against at least one of the 2-OADC enzymes by immunoblotting. Of these, 43 (80%) were positive for IgG, IgM, or IgA class antibodies against the E2 subunit of PDC (PDC-E2) by immunoblotting. Thirty-six of the 54 sera (67%) showed identical results in all of the four assays, and 40 (74%) were all negative or positive by EMA, ELISA, and immunoblotting in PDC-relevant reactivity. There was a significant correlation between the number of detected immunoglobulin classes of anti-PDC-E2 by immunoblotting and anti-PDC by EMA (P < 0.0001), and a significant inverse correlation between IgG class anti-PDC by ELISA and units of PDC activity by EMA (r = -0.87, P < 0.0001).


CONCLUSIONS
Although EMA had lower sensitivity compared with immunofluorescence and immunoblotting, this assay should be included among the routine diagnostic tools for the detection of AMA specific to PBC in clinical laboratories because of its high specificity, objective read-out, and rapid turnaround time.
Hazama
Hiroaki
H
Second Department of Internal Medicine, Nagasaki University School of Medicine, Graduate School of Pharmaceutical Science, Nagasaki University, Nagasaki, Japan.
Omagari
Katsuhisa
K
Masuda
Jun-Ichi
J
Ohba
Kazuo
K
Kinoshita
Hideki
H
Matsuo
Isao
I
Isomoto
Hajime
H
Mizuta
Yohei
Y
Murase
Kunihiko
K
Murata
Ikuo
I
Kohno
Shigeru
S
D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D015151:Immunoblotting; D008105:Liver Cirrhosis, Biliary / Q000175:diagnosis*; D008297:Male; D008928:Mitochondria / Q000276:immunology; D011768:Pyruvate Dehydrogenase Complex / Q000276:immunology
D011768:Pyruvate Dehydrogenase Complex