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Introduction to Laboratory Medicine

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Introduction to Laboratory Medicine Roger L. Bertholf, Ph.D. – PowerPoint PPT presentation

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Title: Introduction to Laboratory Medicine


1
Introduction to Laboratory Medicine
  • Roger L. Bertholf, Ph.D.

2
Some SHJ Lab Statistics
  • Number of employees 130
  • Number of tests/year 1.5 million
  • Yearly budget 16 million
  • Yearly revenue 70 million
  • Net 25 million

3
Laboratory organization
  • Core Laboratory (73 of volume)
  • Chemistry, hematology, toxicology,
    immuno-chemistry, special chemistry, coagulation,
    urinalysis
  • Microbiology (16 of volume)
  • Blood/urine cultures, serology
  • Transfusion Services (3 of volume)
  • Blood typing and cross-matching

4
Chemistry
  • Electrolytes, glu, BUN, creat, phos, TP, Bili,
    Mg, Ca, cholesterol, triglycerides, etc.
  • Blood gases pO2, pCO2, pH, calc. Parameters
  • Immunochemistry endocrine, specific protein,
    tumor markers
  • Toxicology DAU, TDM
  • Urinalysis
  • Special Chemistry electrophoresis, L/S ratio,
    FLM, osmometry

5
SHJ Chemistry Instruments
  • Roche/Hitachi Modular and 914
  • Chemistries and homogeneous immunoassays
  • Roche Elecsys 2010
  • Heterogeneous immunoassays
  • NOVA M (whole blood gas/electrolytes)
  • Abbott IMx
  • Yellow Iris

6
Hematology
  • CBC/Diff
  • Coagulation
  • Microscopy

7
SHJ Hematology Instruments
  • Abbott Cell Dyne 4000
  • CBC, Auto differential
  • Organon Technika MDA
  • Coagulation

8
Microbiology
  • Cultures
  • Blood
  • Urine
  • Sputum, wound, etc.
  • Antibiotic sensitivity
  • Serology
  • Viral Ab, Ag testing

9
Point of Care Testing
  • Instruments are available that can perform
    certain tests at remote locations, such as at the
    bedside on in a clinical care unit
  • Blood glucose
  • Urinalysis
  • Blood gases
  • Electrolytes/BUN/Creatinine
  • Cardiac markers (Troponin I T, CK-MB)
  • Coagulation (ACT)
  • POC tests are nearly always more expensive, than
    the same tests performed in the central laboratory

10
POCT at SHJ
  • Blood glucose (Not under lab license)
  • Electrolytes on the GEM Premier in the OR
  • ACT in the OR and Cardiac Catheterization Lab
  • Urinalysis (not under lab license)

11
Reasons for POC testing
  • Tests are of urgent importance, and results will
    affect the immediate management of the patient
  • Blood gases, electrolytes
  • Tests are so common, simple and cheap that it is
    more economical to perform them at the point of
    care
  • Blood glucose, urinalysis

12
SHJ Blood Gas Lab
  • Operated by Respiratory Therapy
  • Performs blood gases and whole blood
    electrolytes/BUN/Creatinine/Glucose
  • Gases fall under RT license
  • Chemistries fall under the lab license
  • Serves MICU, CCU, PICU, NICU, SICU
  • Performs all co-oximetry

13
Steps in obtaining a laboratory test
  1. Written order is placed
  2. Specimen is collected and properly labeled
  3. Specimen and order are transported to the lab
  4. The specimen is accessioned in the lab
  5. The specimen is processed
  6. The specimen is analyzed
  7. The results are reviewed and verified by an MT
  8. The results are released to the patients record

14
How long steps 4-7 take (P1 orders)
15
How long steps 4-7 take (STAT)
16
Sources of error in laboratory results
  • Pre-analytical
  • Analytical
  • Post-analytical

17
Pre-analytical errors
  • Collection
  • Was the right tube used?
  • Was venipuncture performed correctly?
  • Was the specimen properly stored?
  • Identification
  • Was the blood collected from the correct patient?
  • Was the blood correctly labeled?
  • Patient name, ID, date, time of collection,
    phlebotomist

18
Collection tubes
  • Red-top tubes contain no anticoagulants or
    preservatives
  • Red-top tubes are used for collecting serum
  • 10-15 minutes is required to allow blood to clot
    before centrifuging
  • Used for blood bank specimens, some chemistries

19
Collection tubes
  • Gold (and tiger) top tubes contain a gel that
    forms a physical barrier between the serum and
    cells after centrifugation
  • No other additives are present
  • Gel barrier may affect some lab tests

20
Collection tubes
  • Gray-top tubes contain either
  • Sodium fluoride and potassium oxalate, or
  • Sodium iodoacetate
  • Both perservatives stabilize glucose in plasma
  • NaF/oxalate inhibits enolase
  • Iodoacetate inhibits glucose-3-phosphate
    dehydrogenase

21
Collection tubes
  • Green-top tubes contain either the sodium or
    lithium salt of heparin
  • The amount of Na or Li is insignificant
  • Heparin inhibits thrombin, so blood does not clot
    (plasma)
  • The advantage of plasma is that no time is wasted
    waiting for the specimen to clot

22
Collection tubes
  • Lavender-top tubes contain EDTA, which chelates
    calcium and inhibits coagulation
  • Used for hematology, and some chemistries

23
Collection tubes
  • Blue-top tubes contain sodium citrate, which
    chelates calcium and inhibits coagulation
  • The blood/anticoagulant ratio must be precisely
    known, since the tubes are used for coagulation
    studies.

24
Collection tubes
  • Brown and Royal Blue top tubes are specially
    cleaned for trace metal studies
  • Brown-top tubes are used for Pb analysis
  • Royal blue-top tubes are used for other trace
    element studies (acid washed)

25
Plasma/Serum differences
  • Plasma concentration greater than serum
  • Ca (0.9), LD (2.7), TP (4.0)
  • Plasma concentration less than serum
  • Alb (-1.3), ALKP (-1.6), HCO3- (-1.8), CK
    (-2.1), PO4 (-7.0), K (-8.4)

26
Prolonged venous stasis
  • Increases TP, Fe, cholesterol, AST, bilirubin
  • Decreases potassium

27
Supine vs. sitting or standing
  • The following may decrease by 5-15 in the supine
    patient
  • Total protein
  • Albumin
  • Lipids
  • Iron
  • Calcium
  • Enzymes
  • Ig
  • Thyroxine

28
Significantly affected by hemolysis
  • Total protein, albumin, lipids, iron, calcium,
    enzymes, bilirubn, cholesterol, triglycerides,
    norepinephrine, renin, aldosterone, potassium,
    magnesium, phosphorous

29
Specimens requiring special handling
  • Should be placed immediately on ice
  • Lactate
  • Ammonia
  • Acid phosphatase
  • Plasma catecholamines

30
Exertion-related changes
  • Recent strenuous exercise increases
  • Acid phosphatase, ALT, AST, creatinine,
    phosphorous, CK
  • Recent strenuous exercise decreases
  • Iron, lipids, potassium

31
Other factors affecting lab results
  • Diurnal variations
  • Cortisol, iron, estriol, glucose, catecholamines
  • Age
  • Creatinine, BUN, ALKP, drug metabolism
  • Smoking
  • Ammonia, CO-Hb

32
Specimen identification
  • One of the commonest sources of erroneous lab
    results is misidentified specimens
  • CAP and other accrediting agencies require the
    lab to have a clear and rational policy for
    identifying specimens, and handling misidentified
    specimens
  • The blood bank has stricter requirements for
    specimen identification

33
Misidentified specimens at SHJ
29 Delay in obtaining lab results 26 Specimen
collected/labeled/registered with wrong
patient 46 Specimen unlabeled/mislabeled/labeled
incompletely
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