Myocardial infarction (MI), commonly referred to as a heart attack, is a major global health concern and a leading cause of death and disability worldwide. It occurs due to an acute interruption of blood supply to a portion of the myocardium, most often resulting from coronary artery occlusion (1). Prompt diagnosis and early therapeutic intervention are essential to reduce myocardial damage and improve survival outcomes (2).

Cardiac biomarkers play a pivotal role in the diagnosis and risk stratification of MI. Among these, Troponin I is considered the most sensitive and specific marker for myocardial injury. It is released into the circulation within 3–6 hours after the onset of ischemia and remains elevated for up to 10–14 days, providing a wide diagnostic window (3). Creatine Phosphokinase-MB (CPK-MB), although less specific than troponins, is valuable for detecting reinfarction and assessing the timing of myocardial damage due to its early rise and relatively shorter half-life (4). Lactate Dehydrogenase (LDH), an intracellular enzyme present in myocardial and other tissues, is elevated in the later stages of MI and can serve as a supplementary biomarker in delayed presentations (5).

Despite the growing preference for high-sensitivity troponin assays, the combined evaluation of multiple biomarkers remains beneficial in certain clinical scenarios, especially when the diagnosis is uncertain or in resource-constrained settings (6). This study aims to evaluate the diagnostic utility of Troponin I, CPK-MB, and LDH in patients presenting with acute myocardial infarction and to compare their relative sensitivity and specificity.

A total of 100 adult patients (aged ≥18 years) who were diagnosed with AMI based on clinical symptoms, electrocardiographic changes, and/or elevated cardiac enzymes were enrolled. Patients with recent trauma, hepatic dysfunction, chronic kidney disease, skeletal muscle disorders, or malignancies were excluded to avoid confounding elevations in biomarker levels.

Sample Collection and Biomarker Estimation

Venous blood samples were collected from each patient within 6 hours of chest pain onset. Serum was separated by centrifugation and analyzed for Troponin I, CPK-MB, and LDH levels.

• Troponin I was measured using a chemiluminescent immunoassay (CLIA)-based method.
• CPK-MB levels were estimated using an immunoinhibition technique.
• LDH levels were determined via kinetic UV method.

All assays were performed in the hospital’s central clinical biochemistry laboratory, adhering to standard operating procedures and quality control protocols.

Statistical Analysis

Data were compiled and analyzed using SPSS software version 25.0. Continuous variables were expressed as mean ± standard deviation (SD). Categorical data were presented in percentages. Diagnostic sensitivity and specificity for each biomarker were calculated, and comparisons were made using appropriate statistical tests. A p-value <0.05 was considered statistically significant.

A total of 100 patients diagnosed with acute myocardial infarction (AMI) were included in the study. The demographic distribution revealed a male predominance with 68% males and 32% females. The mean age of the study population was 56.3 ± 11.4 years.

Distribution of Cardiac Biomarkers

Among the biomarkers assessed, Troponin I was elevated in 94 patients (94%) with a mean concentration of 6.5 ± 2.8 ng/mL. CPK-MB was raised in 89 patients (89%), showing a mean value of 56.2 ± 18.7 IU/L. LDH levels were elevated in 78 patients (78%), with a mean value of 621.4 ± 102.5 IU/L. These findings are summarized in Table 1.

Table 1: Mean Values and Positivity Rates of Cardiac Biomarkers in AMI Patients

Gender-wise Comparison

Troponin I levels were significantly higher in males (mean: 6.7 ± 2.6 ng/mL) compared to females (mean: 5.9 ± 2.1 ng/mL). A similar trend was observed for CPK-MB and LDH, though the differences were not statistically significant (p>0.05). The gender-wise distribution is provided in Table 2.

Table 2: Biomarker Levels According to Gender

Sensitivity and Specificity

Troponin I showed the highest sensitivity for diagnosing AMI (94%), followed by CPK-MB (89%) and LDH (78%). Specificity was also highest for Troponin I at 90%. These diagnostic performance metrics are detailed in Table 3.

Table 3: Diagnostic Performance of Cardiac Biomarkers

The present study evaluated the diagnostic utility of three commonly used cardiac biomarkers—Troponin I, CPK-MB, and LDH—in patients presenting with acute myocardial infarction (AMI). Our findings reaffirm the clinical value of these biomarkers, particularly Troponin I, which exhibited the highest sensitivity and specificity for AMI detection.

Troponin I is a regulatory protein specific to cardiac muscle, released in response to myocyte necrosis. It begins to rise within 3–6 hours of myocardial injury and remains elevated for 10–14 days, making it a preferred marker for both early and late diagnosis (1,2). In our study, Troponin I was elevated in 94% of patients, supporting earlier evidence of its diagnostic superiority (3-5).

CPK-MB, though less specific than troponins, remains clinically relevant for early detection and reinfarction monitoring due to its rapid kinetics (6,7). In this study, CPK-MB was elevated in 89% of cases. Studies by Apple et al. and Omland et al. have demonstrated that CPK-MB has moderate diagnostic accuracy but may be influenced by skeletal muscle injury or physical activity (8,9).

LDH, an intracellular enzyme found in many tissues, showed increased levels in 78% of patients. Although LDH lacks specificity, it remains useful in delayed MI diagnosis when Troponin or CPK-MB may have normalized (10,11). Our findings align with those of Bakshi et al., who highlighted LDH’s supplementary value in resource-limited settings (12).

The gender-based comparison in our study showed higher mean Troponin I values in males, consistent with population-based studies reporting sex-related differences in troponin release kinetics (13). However, CPK-MB and LDH did not differ significantly between sexes (14).

From a diagnostic perspective, Troponin I showed the highest sensitivity (94%) and specificity (90%), followed by CPK-MB and LDH. This supports the growing consensus that Troponin assays should be prioritized in AMI protocols (15). However, in scenarios involving early re-infarction or limited access to high-sensitivity assays, combining biomarkers can enhance clinical decision-making.

The limitations of this study include its single-center design, relatively small sample size, and the absence of follow-up for long-term prognostic outcomes. Future studies with multi-center data and larger cohorts are warranted to validate these findings.

The study highlights the diagnostic importance of cardiac biomarkers in myocardial infarction. Among the three markers assessed, Troponin I demonstrated the highest sensitivity and specificity, making it the most reliable indicator for early diagnosis. CPK-MB and LDH also provided supportive diagnostic value, especially in settings with limited access to advanced assays. A combined evaluation approach may enhance diagnostic accuracy and improve clinical outcomes.

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