Detection of creatine kinase macroenzymes

Area of Science:

• Clinical Biochemistry
• Diagnostic enzymology

Background:

• Macroenzymes can cause diagnostic confusion due to spurious enzyme activity elevation.
• Accurate detection of macroenzymes like macro-creatine kinase (CK) is vital in patient plasma or serum.
• A macroenzyme detection service is available to UK laboratories.

Purpose of the Study:

• To report a 10-year laboratory experience with macro-creatine kinase (CK) detection.
• To evaluate the effectiveness of current detection methods and propose improvements.

Main Methods:

• Macro-CK presence was assessed using polyethylene glycol percent precipitable activity (%PPA) and isoenzyme electrophoresis (IsoEP).
• A retrospective review of accumulated findings over a 10-year period was conducted.
• Statistical analysis included Spearman correlation and receiver operating characteristic (ROC) curve analysis.

Main Results:

• Out of 255 requests, 30 patients (11.8%) tested positive for macro-CK (28 type 1, 2 type 2).
• Positive macro-CK cases showed modest total CK elevation.
• %PPA positively correlated with macro-CK presence determined by IsoEP and densitometry (Spearman r(s) = 0.631).

Conclusions:

• Increasing the upper reference limit for %PPA of CK from 37% to 45% enhances cost-effectiveness.
• Over 80% of macro-CK type 1 positive cases were female, aligning with autoimmune process findings.
• Revised detection protocols can improve diagnostic accuracy and laboratory efficiency.