In addition to CK-BB, "macro" forms of creatine kinase will also give
spuriously elevated values for CK-MB when measured by anti-CK-M
immunoinhibition methods.  Macro CK's are classified as type 1
(immunoglobulin-bound CK, usually CK-BB with IgG) or type 2 (oligomeric
mitochondrial CK).   Referring to Tietz's Textbook of Clinical Chemistry
(3rd ed.), Type 1 has been associated with GI diseases, adenoma and
carcinoma, myocardial and vascular diseases and other life-threatening
conditions, occurs more often in women over age 50, and is associated with a
higher mortality.  Type 2 macro CK is found most often in severely ill
adults with malignancies or liver disease or in children with myocardial
disease and is usually associated with a poor prognosis.

If you only want to know if this sample contains CK-MB and at what
concentration, then the best thing to do is use a specific monoclonal
antibody immunoassay for CK-MB.  But if you want to determine precisely what
form(s) of CK this sample contains, then you would need to perform CK
electrophoresis. The bands for macro forms of CK are usually (not always)
separated from CK-MM, -MB, and -BB.  We have not performed electrophoresis
for CK isoenzymes for several years, but I remember that on the Beckman
gels, macro CK type 1 usually migrates between the MM and BB bands (if
IgG-bound) and type 2 migrates anodally to the MM band.  I have also seen a
few cases of type 1 macros (IgA-bound) with the same electrophoretic
mobility as CK-MB.

Salvador F. Sena, Ph.D., DABCC
Associate Director, Clinical Chemistry
Department of Pathology and Laboratory Medicine
Danbury Hospital
Danbury, CT 06810  USA
[log in to unmask]

> -----Original Message-----
> From:	[log in to unmask]
> [SMTP:[log in to unmask]]
> Sent:	Thursday, October 26, 2000 8:40 AM
> To:	[log in to unmask]
> Subject:	RE: CKMB problem
> 
> I note both CK tests are reported in units. The activity based assay for
> CKMB works by inhibiting the CK-M subunit, measuring B and then
> multiplying by 2 to get a CKMB activity. Therefore if you have a lot of
> CK-BB, you get wierd results - This sample could be the results of having
> 725 UNits of the total CK activity due to BB subunit ? a brain injury???
> 
> TIM
> 
> **************************************************************************
> *************
> Prof. T. Reynolds,
> Clinical Chemistry Dept,
> Queens Hospital,
> Belvedere Rd.,
> Burton-on-Trent,
> STAFFS,
> DE13 0RB.
> ---------
> Tel:  +44 (0)1283 511511 ext. 4035
> Fax: +44 (0)1283 593064
> -----------
> [log in to unmask]
> 
> -----Original Message-----
> From:	c=GB;a=NHS;p=NHS NATIONAL
> INT;dda:RFC-822=acb-clin-chem-gen-request(a)mailbase.ac.uk; 
> Sent:	Thursday, October 26, 2000 2:37 PM
> To:	c=GB;a=NHS;p=NHS NATIONAL
> INT;dda:RFC-822=acb-clin-chem-gen(a)mailbase.ac.uk;
> Subject:	CKMB problem
> 
> 
> A recent request for CKMB revealed a total CK of 778 IU/L and a CKMB of
> 1449 
> IU/L (both were measured using Roche reagents). Other tests and controls
> in the 
> batch did not reveal any such anomalies.
> I have a vague recollection of this sort of effect possibly being caused
> by 
> binding of the enzyme to an immunoglobulin.
> 
> Any other ideas?
> 
> Dr D G Williams
> FRCPath
> 
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