| ObjectiveTo explore the values of combined determination of cardiac troponin I (cTnI), myoglobin (MYO) and creatine kinase isoenzyme MB mass (CK-MB mass) as well as combined measurement of creatine kinase (CK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and alpha-hydroxybutyrate dehydrogenase (α-HBDH) in the diagnosis of viral myocarditis (VMC), and to study early and specific markers to diagnose myocardial injury in patients with VMC. MethodsThe myocardial injury markers (cTnI, MYO and CK-MB mass) and myocardial enzymes (LDH, AST, CK andα-HBDH) of 136 patients with VMC, 147 patients with non-viral myocarditis (NVMC) and 120 healthy subjects were determined by the microparticle chemiluminescent immunoassay and the continuous monitoring assay, respectively. Diagnostic efficiency was calculated by the matrix decision method.Results(1) The study revealed that patients with VMC group had strongly higher concentrations of cTnI, MYO and CK-MB mass compared to those with NVMC group and controls (analysis of variance [ANOVA], P<0.01), the levels of cTnI, MYO and CK-MB mass were (0.46±0.28)μg/L, (98.7±38.2)μg/L and (6.2±4.2)μg/L for VMC group, (0.06±0.05)μg/L, (39.6±26.8)μg/L and (2.2±1.7)μg/L for NVMC group and (0.07±0.04)μg/L, (36.7±22.4)μg/L and (2.1±1.3)μg/L for controls.(2) The serum levels of CK, LDH, AST andα-HBDH were obviously higher than that of the controls (225.7±92.9 vs 136.0±76.1 U/L, 234.4±90.3 vs 162.8±77.7 U/L, 50.2±25.7 vs 19.4±12.1 U/L and 206.6±86.4 vs 132.4±66.0 U/L, respectively, P<0.01). However, there was no significantly difference in the serum levels of LDH between VMC group and NVMC group (234.4±90.3 vs 211.6±82.7 U/L, P>0.05). There were significantly difference in the serum activities of LDH and AST between NVMC children and healthy subjects (211.6±82.7 vs 162.8±77.7 U/L and 33.7±19.0 vs 19.4±12.1 U/L, respectively, P<0.01).(3) The diagnostic efficiency of combined determination of cTnI, MYO and CK-MB mass or CK, LDH, AST andα-HBDH for VMC was 90.44% vs 82.35% for sensitivity (SE), 80.95% vs 68.71% for specificity (SP), 81.46% vs 70.89% for positive predictive value (PPV), 90.15% vs 80.80% for negative predictive value (NPV) and 85.51% vs 75.21% for accuracy (AC), respectively. The SP, PPV, NPV and AC of three myocardial injury markers in combination were higher than that of the combination of four myocardial enzymes (P<0.05～0.01). As to the SE, however, no significant difference existed between the two methods (P>0.05).(4) For preliminary diagnosis of VMC, the SE of MYO was the highest (68.38%) and the SE of cTnI was secondary (65.44%) and the SE of CK-MB mass was the lowest (55.88%); the SP of cTnI and CK-MB mass, however, were a better choice (100% and 96.60%, respectively) compared to that of MYO (82.31%) by these three myocardial injury markers.(5) Restoration of MYO was the earliest while cTnI was the latest during convalescence of the patients. The abnormal ratio of MYO reduced quickly from 68.38% of the first day to 26.12% of third day. But the cTnI increased to the peak of third day (0.50±0.31μg/L) and maintained above one week at higher levels. The abnormal ratio of cTnI reduced gradually from 63.89% of ninth day to 32.31% of fourteenth day. The decrease of abnormal ratio of CK-MB mass was secondly from 61.94% of third day to 15.74% of ninth day. ConclusionThe specificity of cardiac enzymes is lower in distinguishing VMC from NVMC. For preliminary diagnosis of VMC, the SE of MYO is higher, but the SP of MYO is lower, and positive persistence time is shorter; the SP of cTnI and CK-MB mass are better as well as positive persistence time is longer, but the SE of cTnI and CK-MB mass are lower. Combined and uninterrupted determination of the myocardial injury markers can provide better diagnostic accuracy.
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