MYOCARDIAL INFARCTION DIAGNOSIS

Introduction

Several new biochemical markers have been investigated for the early and accurate diagnosis of myocardial infarction (MI). Of the commercially available assays, myoglobin and iso- forms of creatine kinase are regarded as the earliest markers of MI. However, the clinical specificity of both is questionable, false positive having been reported in patients with renal failure or skeletal muscle damage. Cardiac Troponin-T, in contrast has been reported as the most specific marker of MI. Although most early investigation showed specificity of Troponin-T for cardiac damage, the problem of increased concentration of Tropoinin-T in renal disease was not addressed. Troponin-I has also been reported to have a very high specificity for cardiac disease. Recent study showed no increase of Troponin-I inpatients with acute or chronic skeletal muscle disease or chronic renal failure. Troponin-I concentration is above the reference range within 6 hours after the onset of chest pain, peaks at 12 hours, and remains increased for long time after the onset of symptoms, it also releases in complex form. Because of its high specificity, Tropoini-I has been shown to be an excellent market for diagnosis for preoperative myocardial infarction.

A. Patient's clinical history
B. Interpretation of cardiogram ( ECG)
C. Measurement at serum of levels of cardiac enzymes/protein eq. CKMB, LDH, Myoglobin, Troponins. These various enzymes/proteins released from myocardial cells after an insult such as ischemia or infarct.

CKMB: CKMB is the serum cardiac marker relied upon as the diagnostic reference standard for acute myocardial infraction but its diagnosis utility is limited because of ..... It lacks specificity (False positive & false negative)

Roles of cardiac Troponins in evaluation of patients with chest pain

Three proteins (Troponin-I, Troponin-T & Troponin-C) are involved in process of cardiac myofibril contraction and relaxation.

Now scientifically it has been proved that

  • Troponin-T is not more sensitive then CKMB for acute myocardial infraction
  • Troponin-T is not more specific than CKMB for AMI
  • Serum levels of Troponin-T remain elevated longer than levels of CKMB.
  • Troponin-T assays are a valuable diagnostic tool.

Where as

  • Troponin-I is at least as sensitive as CKMB for AMI
  • Troponin-I is superior to CKMB in specificity for AMI.
  • Levels of Troponin-I remain elevated longer than levels of CKMB.
  • Troponin-I assays are a valuable diagnostic tool.
  • Troponin-I found to be more specific marker for AMI. The abnormal level of Troponin-I represent true infarction.

NANO TROPONIN-I CARD Test

Principle

The TROP-I kit is the newer lateral flow membrane based immunochromatographic assay. The test uses a monoclonal antibodies, colloidal gold conjugate and an immobilized polyclonal antibody to precisely identify the presence of Troponin-I with great sensitivity and specificity. The sample flows through the dye conjugate and in the presence of the antigen (Troponin-I) an antibody-antigen complex forms. This complex migrates laterally along the membrane and is captured by the immobilized antibody producing a pink/purple land at 'T'. The remaining conjugate continues to migrate to another immobilized control antibody forming a pink/purple band at 'C', indicating proper performance of the test. If no Troponin-I in present, only a band in the control area 'C' appears and no band appear at 'T'

Procedure

  • Take TROP-I test device and place on flat surface.
  • Using provided dropper, add 2-3 drops of serum in sample well (S).
  • The test results should be read after 10 minutes, but within 30 minutes after sample addition.
  • Interpretation of Results

    Positive: Appearance of two pink/purple bands, one each in 'T' and 'C' region indicates that sample contains Troponin-I.

    Negative: Appearance of only one colored band in the 'C' region indicates that the sample is negative for Troponin-I.

    Invalid: If there is no distinct pink/purple band visible in the 'C' region, the test is invalid and should be repeated.

    Sensitivity

    TROP-I test was run against an assayed commercial control sample and found to give positive result at levels as low as 1 ng/ml of Troponin-I

     

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