Introduction: PBC is almost invariably associated with M2-AMA positivity. We report a series of 4 patients who presented with a PBC-like syndrome, with positive AMA and invariably elevated IgM, in whom the M2 sub-fraction was negative by immunoblot technique. Subsequent external testing for M2 by ELISA was positive
Methods: A retrospective review was performed on 4 patients with cholestatic liver blood tests, with positive AMA and negative M2 sub-fractions by immunoblot. Clinical, biochemical and immunological data was analysed.
Results:
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*Biopsy consistent with PBC
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AMA
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Titre
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IGM
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Cholestatic
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SMA
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LKM
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ANF
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Titre
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Liver
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Elevated
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LBT's
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Biopsy
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Case 1
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Yes
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1:320
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Yes
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Yes
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-ve
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-ve
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-ve
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N/A
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Yes*
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|
|
|
Case 2
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Yes
|
1:300
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No
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Yes
|
-ve
|
-ve
|
+ve
|
1:40
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Yes*
|
|
|
|
Case 3
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Yes
|
1:320
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Yes
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Yes
|
-ve
|
-ve
|
-ve
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N/A
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No
|
|
|
|
Case 4
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Yes
|
1:320
|
Yes
|
Yes
|
-ve
|
-ve
|
-ve
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N/A
|
No
|
|
|
Conclusions: ELISA assay for detection of M2 sub-fractions in anti-mitochondrial antibody positive patients with PBC-like syndrome is the most sensitive and reliable laboratory technique currently available. Analysis by ELISA should be undertaken in all patients with positive AMA but apparently negative M2 sub-fractions, in whom PBC is strongly suspected clinically.
