Value of serum muscle enzymes in the differential diagnosis of myopathies

Abstract

Objective To explore the expression differences of serum muscle enzymes among different types of myopathies and viral hepatitis.  Methods This study enrolled 578 patients with myopathies and 51 patients with viral hepatitis from January to September 2018. Serum muscle enzymes [creatine kinase (CK), lactic dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and AST/ALT ratio] were detected in all patients, and the expression differences of serum muscle enzymes were compared among different types of myopathies, and between myopathies and viral hepatitis.  Results In myopathy patients, there were significant differences on the values of CK (χ² =107.710, P = 0.000), LDH (χ² = 36.832, P = 0.000), AST (χ² = 47.608, P = 0.000) and ALT (χ² = 31.722, P = 0.000) among different types of myopathies. Patients with muscular dystrophy had significantly higher expression of CK and LDH than inflammatory myopathy (Z = 9.297, P = 0.000; Z = 2.475, P = 0.040) and metabolic myopathy (Z = 6.765, P = 0.000; Z = 5.983, P = 0.000), higher expression of AST than metabolic myopathy (Z = -5.363, P = 0.000), and higher ALT than inflammatory myopathy (Z = 5.619, P = 0.000). The value of LDH in metabolic myopathy patients was significantly higher than that in inflammatory myopathy (Z = 4.590, P = 0.000). Compared with patients with viral hepatitis, myopathy patients had significantly increased CK (Z = -10.975, P = 0.000), LDH (Z = -6.967, P = 0.000) and AST/ALT ratio (Z = -5.605, P = 0.000), and decreased ALT (Z = 3.949, P = 0.000). Receiver operating characteristic (ROC) curve showed the area under the curve (AUC) of CK, LDH, AST, ALT and AST/ALT ratio were 0.943 (95% CI: 0.919-0.966, P = 0.000), 0.818 (95%CI: 0.756-0.881, P = 0.000), 0.446 (95%CI: 0.350-0.542, P = 0.217), 0.323 (95% CI: 0.224-0.422, P = 0.000), 0.745 (95% CI: 0.671-0.819, P = 0.000), respectively. In the differential diagnostic test between myopathies and viral hepatitis, the sensitivity of CK and ratio of AST/ ALT was 0.880 and 0.512, the specificity of which was 0.961 and 0.882, the maximum Youden index of which was 0.841 and 0.394. Conclusions The serum muscle enzymes spectrum in different types of myopathies were different, but there existed some rules, which could provide clues for clinical classification of myopathies. The ratio of AST/ALT had suggestive values in the differential diagnoses between myopathies and viral hepatitis. For patients with increased transaminase of unknown reasons, serum CK should be detected.

DOI: 10.3969/j.issn.1672-6731.2019.05.006