Chapter 11 Clinical Laboratory Instrumentation
Chapter 11 Clinical Laboratory Instrumentation
Chapter 11 Clinical Laboratory Instrumentation
- Clinical Laboratory : responsible for analyzing patient specimens in order to provide information to aid in the diagnosis of disease and evaluate the effectiveness of therapy - Hospital Department :
Dept. of Clinical Pathology Dept. Of Laboratory Medicine
- Major Section :
Chemistry, Hematology, Microbiology, Blood bank
CLINICAL LABORATORY
Chemistry section
Analysis on blood, urine, CSF, and other fluid To determine clinically important substances Most applications of electronic instrumentation in the clinical laboratory
Hematology section
Determination of numbers and characteristics of the formed elements in the blood (RBC, WBC, and PLT) Tests of function of physiological systems in the blood (e.g. clotting study) Automated on Coulter Counter
Microbiology section
Studies on various body tissues and fluids to determine whether pathological microorganisms are present Little electronic instrumentation
Blood bank
Little electronic instrumentation
CLINICAL LABORATORY
Accuracy Precision Fast response Laboratory information system (LIS) :
- A LIS is a class of software which handles receiving, processing and storing information generated by medical laboratory processes. These systems often must interface with instruments and other information systems such as hospital information systems (HIS).
11.1 SPECTROPHOTOMETRY
Principle : substances of clinical interest selectively absorb or emit electromagnetic energy at different wavelengths.
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ultraviolet (200 - 400 nm) visible (400 - 700 nm) near infrared (700 - 800 nm)
measures the light transmitted and absorbed as it passes through a sample. use prism or diffraction gratings to break light into spectrum of color
11.1 SPECTROPHOTOMETRY
11.1 SPECTROPHOTOMETRY
Diffraction grating
color()
Fig. 11.1 A diffraction grating showing an incident beam of white light, and a ray of monochromatic light emerging
11.1 SPECTROPHOTOMETRY
Flame Photometer:
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Power source and sample-holder function are combined in the flame Samples emission rather than absorption Only for concentrations of pure metals analyze urine or blood to measure the concentration of K+ and Na+ Li+ , not found in biological sample, used as internal standard
Flame Photometer
Fluorometry
an analytical technique for identifying and characterizing minute amounts of a substance by excitation of the substance with a beam of ultraviolet light and detection and measurement of the characteristic wavelength of fluorescent light emitted. (Fig. 11.3) Advantage : Much greater sensitivity Disadvantage : Sensitivity to temperature and pH of the sample
Core lab design emphasizes automation in the most labor-intensive areas of clinical Front-end automation using a Power Processor (Beckman laboratory testing.
Coulter
Intelligent Aliquotter
Hematology Outlet
Specimen Stockyard
11.3 CHROMATOLOGY
Chromatology : a group of methods for separating a mixture of substances into component parts
useful in determining what drug or drugs have been taken in overdose cases. fixed phase (liquid or solid), mobile phase (gas or liquid) Partition : for liquid stationary phase Adsorption : for solid stationary phase Difference in the rate of movement of components of mixture in the mobile phase, caused by interaction of these components with the stationary phase, are used to separate the components
11.4 ELECTROPHORESIS
Electrophoresis : used in clinical laboratory
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to measure quantities of the various types of proteins in plasma, urine, and CSF (cerebrospinal fluid) to separate enzymes into their component isoenzymes to identify antibodies to serve in a variety of other applications.
Principle : the movement of a solid phase with respect to a liquid (the buffer solution) Factors affecting the speed of migration
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Magnitude of charge Ionic strength of buffer Temperature Time Types of support media
11.5 HEMATOLOGY
Blood Particles
Type RBC PLT
Density (millions/l) 4.6 6.2 (adult male) 4.2 5.4 (adult female) 0.15 0.40
Hematocrit (ht) : 40 54(%) adult men, 35-47% adult women = [ height of packed cell / height of blood ] with centrifuged blood in a tube
11.5 HEMATOLOGY
Electronic Cell Counter
resistance method : Coulter Counter
orifice resistance change size of the blood cell in the orifice bridge circuit output R
Coulter STKS
From Coulter Corp. : Fig.11.11-12 Hgb : 1st dilution of 1:2241:250(lysing agent)
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with lysing agent causes cell membrane of RBC to rupture Drabkins solution : convert Hgb to cyanmethemoglobin WBC count : magnitude of voltage pulse is related to the volume of the WBC Three parallel counting unit, and then voting circuit & averaging circuit Correct the average-count signal for coincidence (passage of 2 or more WBCs at the same time) Cells with volume > 35.9 fl are classified as RBCs Cells with volume = 2~20 fl are classified as PLTs
Coulter STKS
WBC differential count
Flow cytometry approach Lysing agent to remove the RBCs WBC stabilizing agent Triple transducers of low-frequency imepdance(cell volume), high-frequency impedance(internal conductivity), light forward scatter(internal structure and shape) Analyzer computer (Fig. 11.13)
11.5 HEMATOLOGY
Electronic Cell Counter
optical method : angle of scattered light is different for different-size cell