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50 terms

Diagnostic Methods--Cardiac Tests

LLU-PAST 548
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Accuracy
"Trueness," ability to dx. TP + TN / TP+FP+TN+FN
Precision
Replicability
Sensitivity
Ability to accurately identify affected, as percentage--OR-- Percentage of affected that will test positive.
TP / TP+FN
Specificity
Ability to accurately identify unaffected, as percentage--OR-- Percentage of unaffected that will test negative. TN / TN+FP
Positive Predictive Value
Percentage of Positive Tests that are affected.
TP / TP+FP
Negative Predictive Value
Percentage of Negative Tests that are unaffected.
TN / TN+FN
Positive Likelihood Ratio
The "odds" of being affected when test is positive.
Sensitivity / (1-Specificity)
Negative Likelihood Ratio
The "odds" pf being unaffected when test is negative.
(1-Sensitivity) / Specificity
FALTs & 3 classes
Factors Affecting Laboratory Tests Preanalytic, analytic, post-analytic
Two classes of Pre-analytic FALT
In vivo (gender, age, race, diet, diurnal variation)
In vitro: specimen handling, sampling error)
Cardiac biomarker sequence
Myoglobin --> CK/CKMB --> Troponin --> LDH
NSTEMI vs STEMI
Non-ST elevation MI; ST elevation MI
Two STEMI groups
NQMI (No Q-waves current), QwMI (Q-waves current, indicate active MI)
CK-MB (CPK-MB) fx, use & value
Creatine Kinase MB. Phosphorylates creatine to make phosphocreatine. Cardiac marker @ >4.0 ng/mL
CK-MB limitations
Elevated in MD, Skeletal muscle injury, malnutrition, post-marathon, rhabdomyolysis, prostate & breast cancer
CK-MB timeline
4-6 hr, 12 hr, 48 hr
cTn fx, use & values
Cardiac troponin. Regulates calcium binding in cardiomyocytes.Gold standard for ACS, establishes irreversible necrosis. cTnT: >0.1 ng/mL; cTnI: >0.04 ng/mL
cTn limitations
Elevated in CHF, Aortic Dissection;
Hypotension, Arrhythmias, Rhabdo, Myocarditis (CHAD HARM)
cTn timeline
4-8 hr, 24 hr, 5-7 days. AT 12 hr, 100% Sensitivity
Myoglobin fx, use and values
O2-carrying protein in skeletal & cardiac muscle. Earliest marker for AMI. Male: 28-72 ng/mL; Female: 25-58 ng/mL.
Myoglobin limitations
Elevated in muscle damage, post-exercise, alcohol abuse. Need draws q2-3 hr
Myoglobin timeline
2-3 hr, 8-12 hr, 24 hr
LDH fx, use and values
Lactate Dehydrogenase. Converts pyruvate to lactate, releasing NAD+. Late AMI marker.
RATIO of LDH1 : LDH2 > 1 suggests MI.
LDH limitations
Elevated in renal, liver and hemolytic dz. (Best use is in hemolysis)
LDH timeline
24 hrs, 2-3 days, 3-10 days
ASO fx, use & values
Antistreptolysin O. Antibodies to streptolysin-O (also streptokinase, hyaluronidase & DNAse-B) following Rheumatic Fever, Scarlet fever, glomerulonephritis .
Tests for GpA Strep Ix, which may suggest valve dz. Normal Adult: <100 IU/mL. Kids Normal kid: <260 IU/mL
ASO limitations
Elevated after any Strep-A; Endocarditis, glomerulonephritis, & in healthy Strep-A carriers
Blood culture uses & procedure
Tests for bacterial Ix of pericardium (pericarditis) or valves (endocarditis). Most common bacteria are pnemococcus or TB. Pain worse supine, better w\sitting, leaning forward. Take 3 cultures from 3 locations, 2 of 3 must be positive in 3-7 days.
Blood culture procedure
Order 3 separate cultures. 5-7 days
Pair w/ Echo for pericarditis or SBE
Brain Natriuretic Peptide fx & use
BNP is made by the ventricles to reduce pressure (CHF, LVH/RVH). It causes natriuresis and diuresis. Allows you to stage CHF (stages 3 & 4) by NYHA classes
CHF symptoms & Best Test
Dyspnea on exertion, Orthopnea, Fatigue, Edema, Paroxysmal nocturnal dyspnea (PUFFY SWOLLEN SNORER) BNP test
BNP values & limitations
Normal: <100, up to 300 w/ age, female
Abnormal: >300
CHF can exceed 1000
IF positive, ECHO
Lipid Panel Components & Requirements
Cholesterol
Triglycerides
HD Lipoproteins
LD Lipoproeins
VLD Lipoproteins
FASTING
Total Cholesterol fx, lab use, values
Used to make steroids, membranes, vitamin D, bile acids. Tests for CHD & risk of Atherosclerosis
Good: <200
Borderline: 200-239
High: >240
Triglycerides fx, lab use, values
Carried BY lipoproteins FROM gut TO adipocytes. Tests for risk of Atherosclerosis.
Good: <150
Borderline: 150-199
High: 200-499
Plain scary: >500
TG Tx
Over 300: change diet & exercise
AT >500, risk pancreatitis. Medicate
HDL fx, lab use, values
Lipoprotein that transports cholesterol FROM tissues TO liver. HIGH HDL --> LOW CHD risk (inverse risk)
Near-zero risk: >75
Good: >60
Acceptable female: >50
Acceptable male: >40
2X CHD risk: <25
TC & HDL ratio for CHD
The higher the TC:HDL, the greater the risk of atherosclerosis and CHD
LDL fx, test uses and values
lipoprotein that carries cholesterol TO tissues FROM the liver. LDL levels are directly proportional to atherosclerosis and CHD risk
DM and CHD: <70
At risk for CHD: <100
Good: 100-129
Borderline: 130-159
High: >160
Scary: >190
Friedwalds formula & its use
Use when TG >400 to calculate LDL:
LDL = (TC - HDL - VLDL)
The FIVE CHD RISK factors
Smoking, HTN, Low HDL, FamHx premature CHD in male <55 or female <65; Age: Male >45, Female >55
Apolipoprotein Assays
ApA1:ApB -->HDL lipoproteins : LDL lipoproteins
More sensitivity & specificity than HDL : LDL ratio
ApE Assay
3 isoforms, E2, E3, E4; 2 of E2=>CHD risk
Cardio-CRP use
Cardio-C Reactive Protein; Acute phase inflammation marker. Coronary artery endothelial inflammation raises c-CRP
Prevalence
Number of "affecteds" in a population at one time.
Bayes' Theorem
Measures "value" of a test.
(Sen) (Prev) (100)/ (Sen) (Prev) + (1-Spec) (1-Sen)
Screening criteria
Prevalence, Consequences, Treatment, Predictive values, Cost
How often are cardiac markers run?
3X in 12-16 hr
VLDL calculation
TG/5. e.g., if TG = 450, VLDL = 90
Homocysteine
$$ test to identify potential damage to vascular endothelium. CHF & Atherosclerosis marker