Patients who should not be analyzed by algorithm:
(1) patients with history of active heart disease
(2) patients with history of recent surgery or trauma
(3) patients with history of concurrent malignancy
(4) patients receiving immunosuppressive therapy.
For these patients, muscle biopsy may be required to reach a diagnosis.
Serum enzymes studied:
(1) CK in U/L
(2) CK-MB, as per cent of total CK activity (by agarose gel electropheresis)
(3) aldolase in U/L
(4) AST in U/L
ratio of CK-to-AST=
= (CK in U/L) / (AST in U/L)
ratio of CK-to-aldolase =
= (CK in U/L) / (aldolase in U/L)
Diagnostic Groups based on Flow Diagram
normal or neurogenic atrophy
(1) CK, AST and aldolase normal
Duchenne's muscular dystrophy
(2) CK > 14,100 U/L and AST > 38 U/L
atrophic
(1) CK <= 14,100 U/L or AST < 38 U/L (not Duchenne's)
(2) aldolase <= 3.9, or ratio of CK-to-AST <= 0.7 (not myopathic)
polymyositis
(1) CK <= 14,100 U/L or AST < 38 U/L (not Duchenne's)
(2) aldolase > 3.9 and ratio of CK-to-AST > 0.7 (myopathic)
(3) AST > 50, and CK-to-AST ratio < 40, and CK-MB > 2%
myopathy, not otherwise specified (NOS)
(1) CK <= 14,100 U/L or AST < 38 U/L (not Duchenne's)
(2) aldolase > 3.9 and ratio of CK-to-AST > 0.7 (myopathic)
(3) AST <= 50, or CK-to-AST ratio >= 40, or CK-MB <= 2% (not polymyositis)
(4) CK-to-AST ratio <= 44, or CK-to-aldolase ratio <= 124
unclassified myopathy
(1) CK <= 14,100 U/L or AST < 38 U/L (not Duchenne's)
(2) aldolase > 3.9 and ratio of CK-to-AST > 0.7 (myopathic)
(3) AST <= 50, or CK-to-AST ratio >= 40, or CK-MB <= 2% (not polymyositis)
(4) CK-to-AST ratio > 44 and CK-to-aldolase ratio > 124
Limitations
• The normal reference ranges for the enzymes are not given, although they can be inferred from the tabular data given.
• The results of the algorithm would be affected if different analytical methodologies from those used in the paper were used to determine enzyme activity.
