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Miscellaneous > Intro to Labs > Flashcards

Intro to Labs Flashcards

1
Q

When should I order labs?

A
  • Testing to confirm/ eliminate the presence of disease & improve cost-efficiency of screening tests
  • Appropriate and thoughtfully-timed use will allow monitoring of dz and treatment

<10% of Dx is based on labs: expensive, takes time, invasive, sometimes wrong (requires more labs)

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2
Q

Why order labs?

A
  • Establishing a Dx
  • R/O a clinical condition
  • *-MC: to monitor a clinical condition**
  • To monitor a therapeutic intervention
  • To establish prognosis
  • To screen for dz (i.e. dyslipidemia)
  • To confirm effective dosing, reduces chance of toxicity
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3
Q

Potential adverse effects

-Financial burden, physical harm, psychological harm, others

A
  • **Financial: **immediate cost; insurance; occupational; legal
  • **Physical: **minor pain/ hematoma at draw site; moderate: infection at draw site; major: inappropriate interpretation leading to mistreatment
  • **Psychological harm: **= MC; medical office “PTSD;” Coumidin therapy: must F/U qweekly, then q2wks, then qmonthly
  • **Others: **phlebotomist risk
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4
Q

Interpreting labs

A
  • Must be interpreted with caution, taking into account all variables producing the results (every pt is different)
  • Must consider this when comparing pt’s results to the test’s reference range
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5
Q

Reference Range

(not “normal range”)

A
  • Binary result = yes or no (postive or negative)
  • Reference range = interpreted w/in their context; defined by various factors (age, gender, race/ethnicity, pregnancy) -usually on labs sheets according to these factors
  • Useful to get previous labs to compare as baseline

Normal reference range: +2SDs of average

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6
Q

Reference range questions

  1. Are test results outside of a reference range indicative of an underlying problem?
  2. Are test results inside of a reference range indicative of no problem?
A
  1. Not necessarily
  2. Not necessarily
    - Results are suggestive, but not necessarily indicative of the presence or absence of a problem
    - Interpret with caution & within the context of the pt’s background, presentation, historical findings, physical findings
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7
Q

Phlebotomy

A
  • Knowing where to draw blood from
  • Proper disposal of needles and sharps to avoid danger for ourselves & others; stabbing yourself when re-capping a needle is MC
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8
Q

Techniques to Prevent Hemolysis

A
  • Mix all tubes with anticoagulant additives **gently **(vigorous shaking can cause hemolysis) 5-10 x
  • Avoid drawing blood from a hematoma (cells are hemolyzed)
  • If using needle & syringe, avoid drawing plunger back too forcefully (sheer force causes breakdown)
  • Dry the venipuncture site before proceeding
  • Avoid a probing, traumatic venipuncture (one of the MC reasons for hemolysis)
  • Avoid prolonged tourniquet applications (< 2 min; < 1 optimal)
  • Avoid massaging, squeezing, probing a site
  • Avoid excessive fist clenching
  • If blood flow into tube slows, adjust needle position to remain in the center of lumen
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9
Q

Blood Analysis

Fluid vs. cells

A

-Fluid: whole blood, serum, plasma

Plasma: 55% of total blood vol; 91% water, incl proteins like fibrinogen, albumin; nutrients; hormones; electrolytes

-Cells: RBCs, platelets, WBCs
Buffy coat = WBCs (7K-9K/mm3); platelets (250K/mm3) <1%
RBCs = 5 million/mm3 ~45% of total blood vol

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10
Q

Plasma vs. serum

Different tests require different processing of the
collected blood sample

A
  • Plasma: liquid minus blood cells
  • Blood collected in tube w/ anticoagulant, centrifuged to separate cellular portion; plasma is found at the top of tube
  • Serum: plasma minus clotting proteins & cells
  • Blood collected in tube w/o anticoagulant, allowed to clot, then centrifuged; serum is found at top of tube

-**Whole blood: **some tests e.g. CBC are performed on whole blood & analyzed w/o further processing

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11
Q

Basic Metabolic Profile

8 components

A
  • *Electrolytes:**
    1. Glucose
    2. Calcium
    3. Sodium
    4. Potassium
    5. CO2 (Carbon dioxide, bicarbonate)
    6. Chloride
  • *Renal labs**:
    1. BUN (blood urea nitrogen)
    2. Creatinine
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12
Q

BMP

  • Identify
  • What is this missing?
A

A. Na (sodium)

B. Cl (Chloride)

C. BUN (Blood Urea Nitrogen)

D. Glucose

E. K (Potassium)

F. HCO3 (Bicarbonate)

G. Crt (Creatinine)

-Calcium not included in stick figure

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13
Q

Complete Metabolic Profile (CMP)

Include BMP + proteins, hepatic labs

A
  • *Proteins**:
  • Albumin (small protein produce in liver; major serum protein)
  • Total protein (albumin + all other proteins)
  • *Hepatic labs**
  • Alkaline Phosphatase (ALP)
  • Alanine amino transferase; SGPT (ALT)
  • Aspartate amino transferase; SGOT (AST)
  • Bilirubin
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14
Q

Liver Tests

A

A. AST
B. ALP
C. TBili
D. ALT
E. Albumin

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15
Q

CBC (one of the MC ordered)

9 components

Interpretation

A
  1. White blood cell count (WBC) w/ differential
  2. Red blood cell count (RBC)
  3. Hemoglobin (Hgb)
  4. Hematocrit (Hct)
  5. Mean Corpuscular Volume (MVC)
  6. Mean Corpuscular Hgb (MCH)
  7. Mean Corpuscular Hgb Concentration (MCHC)
  8. Platelet Count
  9. Red Cell Distribution Width

-Mildly abnormal CBCs should be intepreted cautiously & in comparison to pt’s past CBC results; 5% of healthy pts may have values out of normal range (repeat in few weeks to see trend if baseline isn’t available) vs. extremes which indicate pathology

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16
Q

Differential

-Bands, other types of leukocytes

A
  • May not be included in a hemogram
  • Usually automated to count cells ~32K; more accurate
  • Manual can pick up unusual/atypical cells to clue into Dx e.g. cell “age” examined through size, structure of nuclear chromatin –> Band cells: immature neutrophils that are made in repair or reaction i.e. a major bacterial infection = left shift
  • **Segmented: **more mature; likely d/t higher number of less mature bands (doesn’t differentiate b/n bands)

-Provides classification of WBC types present on sample: by size, staining activity
-Granulocytes: neutrophils, eosinophils, basophils
Agranulocytes: lymphocytes, monocytes,

17
Q

CBC stick figure

A

*A. WBCs
B. Hemoglobin
C. Hematocrit
*D. Platelets
E. RBC Indices: MCV, MCH, MCHC, etc.
F. WBC Differential

*Some may switch WBCs and Platelets in figure

18
Q

Granulocytes
-Function, increase/decrease

A
  • *neutrophils: (polymorphonuclear lymphocytes, PMNs, polys) – most numerous; primary pathogen-fighting cells; contain phagocytic granules; less mature cells (bands**) indicate Left Shift
  • Increase = acute bacterial infxn
  • Decrease = viral infection
  • *eosinophils:** granules contain major basic protein, enzymes & chemotactic factors; helps control allergic responses (asthma, hay fever), parasites = increase
  • Decrease: severely stressed marrow (shock, severe burns); adrenal corticosteroids
  • *Basophils: **release heparin, histamine & other inflammatory mediators (not phagocytic)
  • Increase: hemolytic anemia (can occur with chicken pox & other conditions like basophilic (mast cell) leukemia & CML)
19
Q

Agranulocytes

-Functions, increase/decrease

A
  • *Lymphocytes: **2nd most numerous cell; B cells create antibodies, T cells control immune resp/ cell-mediated immunity; NK cells kill antigenic cells
  • Increase: severe or chronic viral infections (e.g mononucleosis, CMV) ;chronic inflammatory conditions, ALL, CLL, lymphoma
  • Decrease: AIDS primarily CD4 T cells; chemo; corticosteroids; malignancy
  • *Monocytes:** phagocytic antigen-presenting cells/ create inflammatory mediators; first line of defense for some organisms & cells; helps remove damaged tissues, malignant cells, immunity against foreign substances
  • Increase: malaria, endocarditis, typhoid fever, rocky mountain spotted fever; chronic inflammatory rxns, recovery from cell injury, nonhematopoietic malignancy
  • **Decrease: **hairy cell leukemia
20
Q

WBCs

“Never Let Monkeys Eat Bananas”

A

Neutrophils: most numerous (55-70%)
Lymphocytes: 20-40%
Monocytes: 2-8%
Eosinophils: 1-4%
Basophils: <1%

Low = leukopenia
High = leukocytosis
21
Q

RBCs

A
  • **Hemoglobin: **measures total amt of Hgb in peripheral blood; rapid, indirectly measures RBC count
  • **Hematocrit: **measures % of blood volume made up by RBCs; indirectly measures RBC # and volume, rapid measurement of RBC count
  • **RBC count: **# of circulating RBCs in 1 mm3 of peripheral venous blood
  • Anemia/ Polycythemia = low/ high of these 3 values
  • **Mean Corpuscular Volume: **measurement of avg volume (size) of RBC
  • Microcytic/Macrocytic = low/ high volume
  • **Reticulocyte count: **indicates RBC production by bone marrow (ability to response to anemia & make more) if size/ shape varies widely, indication for manual diff
  • Reticulocytopenia/ reticulocytosis = low/ high count
22
Q

Morphology

A

**-Granulocytes with cytoplasmic organisms: **fungal/ bacterial infections

**-Reactive lymphocytes: **viral infections

**-Hypersegmented neutrophils: **pernicious anemia

**-Blasts, auer rods: **acute leukemia

-Hypochromic anemia presents as small, centrally pale RBCs; less heme = less ability to carry O2

Miscellaneous (6 decks)

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