Enzyme inhibition assay for pyruvate dehydrogenase complex: Clinical utility for the diagnosis of primary biliary cirrhosis

Table 1 Detection of enzymatic inhibitory antibody to PDC by enzyme inhibition assay in non-PBC s

First author	Year	Case studied	Antigen source	Serum amount (μL)	Serum dilution	Positivity rate (%)1
Teoh	1991	Normal subject, AIH, ALD, RA, SLE	Commercial PDC	1002	0.388888889	0 / 62 (<1.7)
Teoh	1994	Healthy subject, immunopathic diseases	Commercial PDC	1002	0.388888889	0 / 42 (<2.4)
Omagari	1996	Adult blood donors, healthy women	Commercial PDC	2	Undiluted	0 / 186 (<0.6)
Schmit	1999	Healthy controls, viral hepatitis, AIH	TRACE EMA kit	4	Undiluted	0 / 92 (<1.1)
Jois	2000	Normal subject, AIC, AIH, ALD, RA, SLE, etc.	Commercial PDC	2	Undilute	4 / 1055 ( 0.4)
Hazama	2000	Healthy subject, ALD, viral hepatitis, fatty liver	TRACE EMA kit	4	Undiluted	0 / 50 (<2.0)
Jensen	2000	AIH, abnormal LFT patients, Normal blood donors, etc.	TRACE EMA kit	4	Undiluted	0 / 250 (<0.4)
Masuda	2002	Healthy subject, ALD, viral hepatitis, fatty liver, etc.	TRACE EMA kit	4	Undiluted	0 / 130 (<0.8)
Hazama	2002	Healthy subject, ALD, viral hepatitis, fatty liver, etc.	TRACE EMA kit	4	Undiluted	0 / 97 (<1.1)

¹When the numerator is zero, the percentage is calculated as a nominal value of <1. ²100 μL of doubling dilutions of serum from 1:500 in phosphate-buffered saline solution. PDC, pyruvate dehydrogenase complex; PBC, primary biliary cirrhosis; AIH, autoimmune hepatitis; ALD, alcoholic liver disease; RA, rheumatoid arthritis; SLE, systemic lupus erythematosus; EMA kit,Enzymatic mitochondrial Antibody (M2) Assay kit; AIC, autoimmune cholangitis; LFT; liver function tests.

Table 2 Interpretation of detection of anti-2-OADC by immunoblotting and enzyme inhibition assay

Immunoblotting (IgG/IgM/IgA)	Enzyme inhibition assay	Interpretation	Estimated percentage (%)
Positive	Positive	PBC	72 - 83
Positive	Negative	Non-anti-PDC positive PBC	10 - 25
		Immunoblotting false positive?	10 - 15
Negative	Positive	Enzyme inhibition assay false positive?	Very rare
Negative	Negative	Non-PBC	Very rare

These data are based on our results that the sensitivity of immunoblotting for PBC is almost 100%, and the specificity of enzyme inhibition assay for PBC is nearly 100%, i.e., when the result by immunoblotting is negative, the serum is not from PBC, and when the result of enzyme inhibition assay is positive, the serum should be from the patient with PBC. 2-OADC, 2-oxo-acid dehydrogenase complex; PBC, primary biliary cirrhosis; PDC, pyruvate dehydrogenase complex.