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Interpretation of laboratory Tests General & Cardiovascular System. Hadeel Alkofide MSc PHCL 326 May 2011. Learning Objectives. Differentiate between invasive & noninvasive tests State the clinical application of common general diagnostic procedures - PowerPoint PPT Presentation
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Interpretation of laboratory Tests
General & Cardiovascular System
Hadeel Alkofide MScPHCL 326May 2011
Learning Objectives Differentiate between invasive & noninvasive tests
State the clinical application of common general diagnostic procedures
Identify the clinical application of specific laboratory tests
Identify the clinical application of specific diagnostic procedures
Assess common laboratory & diagnostic test results
Introduction
Introduction Data from laboratory & diagnostic tests & procedures
provide important information regarding
The response to drug therapy
The ability of patients to metabolize & eliminate specific therapeutic agents
The diagnosis of disease, & the progression & regression of disease
IntroductionInvasive tests
Require penetration of the skin or insertion of instruments or devices into a body orifice
The degree of risk varies from relatively minor risks such as pain, bleeding, & bruising associated with venipuncture to the risk of death associated with more invasive procedures such as coronary angiography
E.g venipuncture, insertion of a central venous catheter, & collection of cerebrospinal fluid
IntroductionNoninvasive tests
Do not penetrate the skin or involve insertion of instruments into body orifices & pose little risk to the patient
E.g. include chest radiograph, analysis of spontaneously voided urine, & stool occult blood analysis
Introduction The selection of specific tests & procedures depends on
The patient's underlying condition The need for the information The degree of risk
Reference ranges are listed in Tables 5-1 through 5-7 Results are interpreted using laboratory specific reference
ranges Reference ranges may differ among different laboratories
depending on the population & laboratory methodology used to establish the range
IntroductionFactors to consider when interpreting individual test
resultsPatient ageGender Timing of the test result in relationship to drug administration Concomitant drug therapyConcurrent diseases, organ function (renal, liver, cardiac)Test sensitivity (the proportion of true-positive results)Test specificity (the proportion of true-negative results)Timing of the test in relation to drug dosing or known circadian rhythmsGenetics (e.g., glucose-6-phosphate deficiency)Fluid status (e.g., euvolemia, dehydration, fluid overload)
General Organ System Monitoring
General Organ System Monitoring
A variety of tests & procedures are used to diagnose & monitor conditions that affect various organ systems
The applications & uses of these tests & procedures continue to expand with experience & the integration of new technology
General Organ System Monitoring
Angiography
A radiographic test used to evaluate blood vessels & the circulation
Radiopaque material is injected through a catheter & images are recorded using standard radiographic techniques
Biopsy
Removal & evaluation of tissue
General Organ System Monitoring
Angiography
General Organ System Monitoring
Computed Tomography
(CT; CAT scan) uses a computerized X-ray system to produce detailed sectional images
The system is very sensitive to differences in tissue density & produces detailed, two-dimensional planar images
Contrast agents increase attenuation
The spiral or helical CT takes pictures continuously, decreasing the time needed to obtain images
Computed Tomography
General Organ System Monitoring
General Organ System Monitoring
Doppler Echography
Uses ultrasound technology to measure shifts in frequency from moving images
E.g, Doppler echography is used to evaluate blood flow velocity & turbulence in the heart (Doppler echocardiography) & peripheral circulation
General Organ System Monitoring
Doppler Echography
General Organ System Monitoring
Endoscopy
Used to examine the interior of a hollow viscus (e.g., digestive, respiratory, & urogenital organs & the endocrine system) or canal (e.g., bile ducts, pancreas)
The endoscope, a flexible or inflexible tube with a camera & a light source, is inserted into a body orifice (Figure5-1)
Still &/or video images are recorded & tissues obtained for biopsy or other laboratory diagnostic tests
General Organ System Monitoring
Endoscopy: Examples of common endoscopic procedures
Colonoscopy: views the inside of the entire colon from rectum to end of the small intestine
Sigmoidoscopy: views the inside of the large intestine from the rectum through the sigmoid colon
Cholangiopancreatography: views the inside of the bile ducts & pancreas
Esophagogastroduodenoscopy: views the inside of the esophagus, stomach, & duodenum
Bronchoscopy: views the inside of the tracheobronchial tree
General Organ System Monitoring
Fluoroscopy
Uses a fluoroscope, a device that makes the shadows of x-ray films visible, to provide real-time visualization of procedures
It exposes a patient to more radiation than routine radiography but often is used to guide needle biopsy procedures & nasogastric tube advancement
General Organ System Monitoring
Magnetic Resonance Imaging Uses an externally applied magnetic field to align the axis
of nuclear spin of cellular nuclei The patient is surrounded by the magnetic field (Fig. 5-2) Brief radio frequency pulses are applied to displace the
alignment The energy emitted when the displacement ends is
detected resulting in finely detailed planar & three-dimensional images
Contrast agents increase the attenuation
General Organ System Monitoring
Magnetic Resonance Imaging
General Organ System Monitoring
Paracentesis
The removal & analysis of fluid from a body cavity
Plethysmography
Measures changes in the size of vessels & hollow organs by measuring displacement of air or fluid from a containment system
Body plethysmography is used to assess pulmonary function
General Organ System Monitoring
Plethysmography
General Organ System Monitoring
Positron Emission Tomography (PET)
Uses positron-emitting radionuelides to visualize organs & tissues of the body
The radionuclides decay, producing positrons that collide with electrons
A special camera detects photons, released when the positrons & electrons collide
It provides quantitative information regarding the structure & function of organs & tissues
General Organ System Monitoring
Positron Emission Tomography (PET)
General Organ System Monitoring
Single-Photon Emission Computed Tomography. (SPECT) Similar to PET but involves the administration of
radionuclides that emit gamma rays
It is less expensive than PET but provides limited image resolution
General Organ System Monitoring
Standard Radiography (Plain Films, X-Ray Films)
Produces images on photographic plates (Figure 5-3)
These films are sometimes difficult to interpret because the three dimensionality is lost on the planar images
General Organ System Monitoring
Ultrasonography (Echography)
Uses ultrasound (high-frequency waves imperceptible to the human ear) to create images of organs & vessels
Ultrasonography is used to visualize the fetus in uterus
Cardiovascular
Laboratory Tests Cardiac Enzymes
• The pattern & time course of the appearance of enzymes in the blood after cardiac muscle cell damage are used to diagnose MI
Creatine Kinase
Lactic dehydrogenase (LDH)
Troponins
Cardiovascular
Laboratory TestsCardiac Enzymes Creatine Kinase
Found in skeletal & cardiac muscle, brain, bladder, stomach, & colon
Isoenzyme fractions identify the type of tissue damaged
CK-MB(CK2) is found in cardiac tissue
CK-MB is detected in the blood within 3 to 5 hours after a MI
Levels peak in about 10 to 20 hrs & normalize within about 3 days
Cardiovascular
Laboratory TestsCardiac Enzymes Lactic dehydrogenase (LDH)
Found in a variety body tissues
Isoenzyme fractions used to identify type of tissue damage
LDH1- LDH2 are found in the heart, brain, & erythrocytes
LDH 2 accounts for the highest % of total serum LDH
After a MI the rise in LDH 1 > the rise in LDH2
LDH ↑ within 12 hrs after an MI
It Peaks 24 to 48 hrs, & normalizes by about-day 10
Cardiovascular
Laboratory TestsCardiac Enzymes Troponins
A complex of proteins (Troponin I, C, & T) that mediate the actin & myosin interaction in muscle
Troponins I & T are specific to cardiac muscle & are used to identify cardiac muscle injury
Their concentrations ↑ within a few hrs of cardiac muscle injury & remain elevated for 5-7 days
Cardiovascular
Laboratory Tests Cardiac enzymes:
CK-MB = Creatinine Kinase-MyoGlobin
Cardiovascular
Laboratory Tests Cholesterol
Low-density lipoprotein (LDL)is strongly correlated with coronary artery disease
High density lipoprotein (HDL)is inversely correlated with coronary artery disease
Triglycerides Found in very low density lipoproteins (VLDLs) &
chylomicrons
Cardiovascular
Laboratory Tests C-Reactive Protein
It is a biologic marker of systemic inflammation.
Preliminary studies have linked an ↑ C-reactive protein with an ↑ risk of MI, stroke, & peripheral arterial disease
Myoglobin. A small protein found in cardiac & skeletal muscle
The presence of myoglobin in the urine or plasma is a relatively sensitive indicator of cellular damage
Cardiovascular
Diagnostic Tests & Procedures Cardiac Catheterization
Used to evaluate cardiac function
A catheter is passed into the right or left side of the heart
Right-sided catheterization is used to measure right atrial pressures, right ventricular pressures, pulmonary artery pressures, & pulmonary artery occlusion pressure
Left-sided catheterization is used to measure left ventricular pressures
Cardiovascular
Diagnostic Tests & Procedures Chest Radiography.
Chest x-ray films are used to diagnose cardiac disease & monitor the patient's response to drug & nondrug therapy
The chest radiograph is used to determine the size & shape of the atria & ventricles, to calculate the cardiothoracic ratio, & to detect abnormalities in the lung fields & pleural spaces
Coronary Angiography In coronary angiography the cardiac vessels are visualized
by injecting the vessel with a contrast agent
Cardiovascular
Diagnostic Tests & Procedures Echocardiography
Used to evaluate the size, shape, & motion of the valves, & walls & changes in chamber size during the cardiac cycle
Cardiovascular
Diagnostic Tests & Procedures Electrocardiogram (ECG)
Records the electrical activity of the heart (Figure 5-5)
used to diagnose cardiac disease, monitor the patient's response to drug therapy, & monitor for adverse drug effects
12 separate leads, 6 extremity (limb) leads & 6 chest leads create a three-dimensional view of cardiac electrical activity
Cardiovascular
Diagnostic Tests & Procedures Electrocardiogram with Stress (Stress Test)
The ECG is recorded during standardized exercise protocol with gradually increasing level of exercise or with patient at rest after administration of dobutamine or dipyridamole
Either intervention increases myocardial oxygen consumption and blood flow
BP, HR, O2 consumption, O2 saturation, & arterial blood gases are collected to provide a thorough assessment of how the CV system functions under stress conditions
Cardiovascular
Diagnostic Tests & Procedures Electrocardiography
Holter Monitoring (Ambulatory Electrocardiography) A portable recorder to record the ECG continuously
throughout usual patient activity Thallium Stress Test
It combines the parenteral administration of thallium-201, a radionuclide taken up by healthy myocardial tissue, and the stress test (either exercise or pharmacologic)
A gamma camera is used to record serial images of the myocardium
Cardiovascular
Diagnostic Tests & Procedures Technetium-99m Pyrophosphate Uptake.
Infarcted myocardial tissue has an increased uptake of technetium-99m compared with healthy tissue
The isotope is injected parenterally, & serial images of the heart are obtained to evaluate the location & extent of the myocardial infarction
Cardiovascular
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