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Fall 2014 - CM Dermatology > Lab Medicine > Flashcards

Lab Medicine Flashcards

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Dermatology Board Prep flashcards
1
Q

4 Disciplines of Lab Medicine

A
  • hematology
  • chemical pathology
  • microbiology
  • immunology
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2
Q

What types of clinical reasoning go into doing labs?

A
  • why test is being ordered
  • what are consequences of not ordering a lab test
  • how good is the test at differentiating health from disease
  • how are the test results interpreted
  • how will the test results influence patient management
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3
Q

Reference Range

A
  • comparison of a patient’s laboratory test result vs. a reference or “normal” range
  • for some analytes, the range is defined as less than or greater than a certain value
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4
Q

What must be considered when using reference range to interpret a patient’s lab results?

A
  • age
  • gender (eg pregnancy if applicable)
  • lab and technique used
  • situational: geographic, fasting vs nonfasting, medications
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5
Q

Gaussian Distribution

A
  • a bell-shaped curve where the central 95% is typically used as a test’s normal range
  • normal range encompasses mean plus or minus 2 SD
  • roughly 5% of normal patients may be outside the cutoff value
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6
Q

Screening Test

A

-identifies asymptomatic people who may have a disease

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7
Q

Diagnostic Test

A

-determines presence or absence of disease when patient shows signs or symptoms

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8
Q

What are some common disease screenings?

A
  • pap smear for cervical cancer
  • fecal occult blood test for colorectal cancer
  • PSA tests for prostate CA
  • PPD test screens for TB
  • mammography for breast CA
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9
Q

Validity

A

-how well a test distinguishes between who has disease and who does not

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10
Q

Reliability

A
  • consistency of test at different times or under different conditions
  • degree to which results are free from random error
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11
Q

Sensitivity

A
  • measures validity of test
  • disease oriented
  • ability to identify those WITH disease correctly
  • minimizes false negatives
  • SNOUT: sensitivity test with negative results rules out disease
  • # of true positives/(true positives + false negatives)
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12
Q

Specificity

A
  • healthy oriented
  • ability to identify those without disease correctly
  • minimizes false positive
  • SPIN: specific test with positive result rules in disease
  • # of true negatives/(true negatives + false positives)
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13
Q

Principle Function of Circulating Blood

A

transportation

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14
Q

Principle Function of RBCs

A

transport hgb, which carries O2

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15
Q

Principle Function of WBCs

A

involved in defending your body from foreign invaders

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16
Q

Principle Functions of Platelets

A

respond to blood vessel injury to form a clot

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17
Q

Indications for Ordering a CBC

A
  • investigate disease of blood or bone marrow
  • investigate response to inflammation or infection
  • assess sxs of fatigue, pallor, weakness, unexplained bleeding or bruising, dizziness, fever, weight loss
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18
Q

What components are included in CBC?

A
  • WBC count
  • RBC count
  • Hgb
  • Hematocrit
  • MCH, MCHC, MCV
  • RDW
  • platelets
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19
Q

Normal RBC Range

A
  • male 4.73 - 5.49 10^6/ uL

- female 4.15 - 4.87

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20
Q

Mean Cellular Volume

  1. Normal Value
  2. Define
A
  1. 78-98 um^3

2. average volume of RBCs; useful in classifying type of anemia

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21
Q
  1. Increase in Mean Cellular Volume

2. Decrease in Mean Cellular Volume

A
  1. increase MCV = vitamin B12 or folic acid deficiency

2. decrease MCV = iron deficiency anemia

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22
Q

Hemoglobin

A
  • male: 14.40 - 16.60 gm/deciliter

- female: 12.2 - 14.7 gm/deciliter

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23
Q

Hematocrit

A
  • proportion of blood that is made up of RBCs
  • percentage of RBC/total blood volume
  • men 40-54%
  • women 37-47%
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24
Q

Causes of Elevated Hgb

A
  • loss of plasma volume (dehydration)
  • high altitude
  • smokers with COPD
  • congenital heart disease
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25
Q

Causes of Low Hgb

A
  • increased destruction of RBCs
  • decreased production of RBCs
  • blood loss
  • pregnancy
  • vitamin deficiency
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26
Q

WBCs

A

-normal: 4500-11000 cells/mm^3

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27
Q
  1. Granulocytes

2. Agranulocytes

A
  1. neutrophils, eosinophils, basophils

2. lymphocytes, monocytes

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28
Q

Neutrophils/PMN

A
  • 40-76%

- elevated in bacterial infections, inflammatory conditions

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29
Q

Basophils

A
  • 0-1%
  • elevated CML, after splenectomy, polycythemia
  • decreased rheumatic fever, pregnancy, steroid therapy, radiation therapy
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30
Q

Eosinophils

A
  • elevated with allergic or parasitic infection, skin disease
  • NAACP: neoplasma, allergy/asthma, Addisons disease, collagen vascular disease, parasites
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31
Q

Lymphocytes

A
  • 24-44%

- elevated with viral infection

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32
Q

Monocytes

A
  • 3-7%

- elevated with phagocytosis bacterial infections

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33
Q

Causes of Elevated WBCs

A
  • acute bacterial or viral infections
  • leukemia
  • post splenectomy
  • steroids (prednisone)
  • may occur w/o disease: high stress, excitement, pain, trauma, heat)
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34
Q

Causes of Low WBCs

A
  • viral infections
  • overwhelming bacterial infections
  • hypersplenism
  • medications that suppress bone marrow
  • bone marrow suppression
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35
Q

Platelets

A
  • 150,000-400,000/mm^3

- avg life span 7-10 days

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36
Q

Causes of Low Platelets

A
  • enlarged spleen
  • platelet destruction
  • decreased platelet production
  • alcoholism
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37
Q

Causes of Elevated Platelets

A
  • hemorrhage
  • splenectomy
  • inflammation
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38
Q

Urinalysis

A
  • assist in identifying urologic conditions: stone, UTI, malignancy
  • assist in identifying systemic disease
  • midstream, clean catch
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39
Q

Urinalysis: Clarity

A

-cloudy: bacteria, blood, crystals

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40
Q

Urinalysis: Odor

A
  • foul smell with infection (e. coli)

- sweet smell with diabetes (ketones)

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41
Q

Urinalysis: Color of Urine

A
  • red: hematuria, kidney stones, UTI, bladder cancer
  • yellow: dehydration, foods
  • orange: medication side effects
  • brown: glomerulonephritis, myoglobin
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42
Q

Specific Gravity

A
  • 1.001-1.035
  • elevated with volume depletion
  • decreased with excessive fluid intake, diabetes insipidus, diuretic therapy
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43
Q

pH

A
  • 4.6-8.0
  • increased with vomiting, some urinary disease, or kidney disease
  • decreased with aspirin overdose, starvation, alcohol ingestion, high protein diet
44
Q

Urinalysis - Protein

A
  • proteins too large to pass through glomerulus

- associated with glomerulonephritis, pre-eclampsia, screen for complications from DM

45
Q

Urinalysis - Glucose

A
  • serum levels above 150-300 will produce glucose in urine

- associated w/ DM, burns, pancreatitis, corticosteroid use, Cushing’s disease

46
Q

Urinalysis - Ketones

A
  • ketones formed from breakdown of stored fat

- associated with starvation, alcoholism, or diabetic ketoacidosis

47
Q

Urinalysis - Bilirubin

A
  • by-product of hemolysis

- associated w/ biliary obstruction and liver injury

48
Q

Urinalysis - Blood

A

-associated w/ kidney stones, urinary trauma, UTI, strenuous exercise or bladder cancer

49
Q

Urinalysis - Leukocyte Esterase

A
  • detects enzymes released by WBCs

- associated with UTI

50
Q

Urinalysis - Urobilinogen

A
  • bilirubin may react with bacteria in gut to produce urobilinogen
  • associated w/ hemolysis and hepatocellular disease
51
Q

Urinalysis - Nitrites

A
  • some bacteria convert nitrates to nitrites

- positive result = UTI usually

52
Q

Microscopic Urinalysis Exam

A
  • urine microscopic requires centrifuged sample
  • requires lab tech to look for WBC, RBC, proteins, casts
  • WBC: 0-5 per high power field
  • RBC: 0-3 per high power field
53
Q

Microscopic Urinalysis - Proteins

A

-associated w/ multiple myeloma

54
Q

Microscopic Urinalysis - Crystals

A
  • formed from solutes in the urine

- associated w/ kidney stones

55
Q

Microscopic Urinalysis - Casts

A
  • formed in distal convoluted tubule
  • abnormal protein formed during infection of inflammation
  • red cast: glomerulonephritis
  • white cast: pyelonephritis
56
Q

Liver Functions

A
  • conjugate bilirubin
  • synthesis of proteins and clotting factors
  • involved in storage and disposal of nutrients, drugs, toxins
57
Q

Liver Profile - Aspartate Aminotransferase

A
  • 7-42 IU/liter

- elevated with liver, muscle, or cardiac injury

58
Q

Liver Profile - Alanine Aminotransferase

A
  • 1-45 IU/liter

- more sensitive with liver injury

59
Q

Liver Profile - Alkaline Phosphatase

A
  • normal 25-160 IU/L

- elevated with bile duct obstruction (cholecystitis, viral hepatitis, cirrhosis)

60
Q

Liver Profile - Gamma glutamyl transpeptidase

A
  • elevated with liver injury or biliary obstruction

- used as a marker of alcohol use

61
Q

Unconjugated Bilirubin

A
  • bilirubin bound by albumin
  • not water soluble
  • elevated with hemolysis
62
Q

Conjugated Bilirubin

A
  • bilirubin cleaved of albumin
  • water soluble
  • elevated with bile duct obstruction
63
Q

Albumin

A
  • protein made in liver

- marker of liver function

64
Q

Indications for Ordering Coagulation Studies

A
  • unexplained bleeding disorder or excessive bruising
  • consecutive pregnancy loss
  • patients receiving heparin or coumadin therapy
65
Q

Prothrombin Time (PT)

A
  • normal 11.5-13.5 seconds
  • measure extrinsic pathway of coagulation
  • time required for coagulation to occur
  • marker of liver function
66
Q

Partial Thromboplastin Time (aPTT)

A
  • normal 27-38 seconds
  • measures intrinsic coagulation pathway
  • most commonly used to monitor heparin therapy
67
Q

Pancreas Enzymes

A

amylase and lipase

68
Q

Increased Levels of Amylase and Lipase Associated With?

A
  • pancreatitis
  • biliary obstruction
  • pancreatic carcinoma
69
Q

Amylase

A
  • 10-130 U/L

- peaks earlier and declines more rapidly with pancreas inflammation

70
Q

Lipase

A
  • normal < 52 U/L
  • lipase remains elevated longer
  • lipase more specific for pancreatic inflammation
71
Q

Electrolyte Function

A
  • determine overall fluid status

- acid/base status

72
Q

Indications for Ordering Electrolytes

A
  • patients receiving IV fluid
  • metabolic or endocrine abnormalities
  • medications that interfere with electrolytes
  • severe vomiting/diarrhea
73
Q

Sodium

A
  • 136-145 mmol/L
  • major extracellular cation
  • involved with maintenance of blood and body fluids and conduction of impulses
74
Q

Elevated Sodium

A
  • not enough water in body (dehydration)
  • vomiting and diarrhea
  • endocrine
75
Q

Decreased Sodium

A
  • overhydration

- endocrine (Cushing’s)

76
Q

Potassium

A
  • 3.5-5.0 mEq/L
  • major intracellular cation
  • involved in conduction of impulses
77
Q

Elevated Potassium

A
  • cell injury
  • kidney failure
  • endocrine (Addisons)
  • can lead to arrhythmias
78
Q

Decreased Potassium

A
  • malnutrition
  • vomiting, diarrhea
  • diuretic medications
79
Q

Elevated Chloride

A
  • > 107 mEq/L
  • dehydration
  • overactive parathyroid glands
80
Q

Decrease Chloride

A
  • <97 mEq/L

- vomiting

81
Q

Elevated Magnesium

A
  • normal 1.3-2.1 mg/dL
  • kidney disease
  • use of antacids
82
Q

Decreased Magnesium

A
  • inadequate absorption (poor diet, alcoholism, diarrhea)

- medications like diuretics

83
Q

Calcium

A
  • normal 8.2-10.2 mg/dL
  • most stored in bone 99%
  • half in circulation is protein bound, other half ionized
  • only ionized Ca is metabolically active
  • important in muscle contraction, cardiac function, nerve impulse, blood clotting
84
Q

Elevated Calcium

A
  • hyperparathyroid hormones
  • cancer
  • excessive vitamin D
85
Q

Decreased Calcium

A
  • hypoparathyroid hormones
  • deficient protein
  • vitamin D deficiency
86
Q

Glucose

A
  • formed from carb digestion and conversion of glycogen to glucose by the liver
  • insulin decreases blood glucose
  • glucagon increases blood glucose
  • fasting blood glucose (<110, impaired 110-125)
  • elevated glucose may be sign of DM, endocrine disorders, prednisone therapy, pancreatitis
87
Q

Hgb A1C

A
  • normal <5%
  • measures glycosylated hemoglobin
  • reflects the average blood glucose [ ] over past 2-3 months
  • useful in monitoring DM management
88
Q

Blood Urea Nitrogen (BUN)

A
  • normal 5-20 mg/dL
  • urea is produced in liver as waste from protein breakdown
  • urea has to be filtered by the kidneys and is excreted in urine
89
Q

Elevated BUN

A
  • impaired kidney function
  • increased protein catabolism
  • dehydration
90
Q

Decreased BUN

A
  • liver failure (less urea produced)
  • malnutrition
  • endocrine disorders
91
Q

Creatinine

A
  • normal 0.9-1.2 men and 0.6-1.1 women
  • production is constant and correlates directly with muscle mass
  • assesses renal function
92
Q

Elevated Creatinine

A
  • impaired renal function

- large muscle mass

93
Q

Decreased Creatinine

A
  • decreased muscle mass

- liver disease

94
Q

Uric Acid

A
  • normal 3.4-8.0 mg/dL men, 2.4-6 women
  • end product of purine metabolism
  • most uric acid is excreted by the kidneys
95
Q

Increased Uric Acid

A
  • excessive cell breakdown of nucleonic acids (gout)
  • excessive destruction of cells (leukemia)
  • inability to excrete uric acid (renal failure)
96
Q

Thyroid Gland

A
  • regulates metabolic activity

- involves interaction between hypothalamus, anterior pituitary, thyroid gland

97
Q

TSH

A
  • 0.4-4.8 mIU/L
  • most sensitive test for screening thyroid disorders
  • elevated = hyperthyroid
  • decreased = hypothyroid
98
Q
  1. T4

2. T3

A
  1. 0.8-1.7 ng/dL
  2. 80-200 ng/dL

elevated T4/T3 = hyperthyroid
decreased T4/T3 = hypothyroid

99
Q

Cultures

A
  • involve growing microorgs or living tissue cells on a special medium to support growth of the material
  • allow specific microbial identification
  • collected and performed prior to beginning abx therapy
100
Q

Blood Culture

A

-when suspected bacteremia present

101
Q

Urine Culture

A

-when suspected UTI or pyelonephritis

102
Q

Throat Culture

A

-gold standard for strep pharyngitis

103
Q

Sputum Culture

A

-dx and tx of pneumonia and TB

104
Q

Sed Rate

A

-marker of inflammation

105
Q

D-dimer

A
  • marker of clotting process

- useful to screen for venous thrombosis (DVT)

106
Q

Brain Natriuretic Peptide (BNP)

A
  • hormone produced by ventricles of the heart
  • increased with ventricular volume expansion and pressure overload
  • increased with CHF

Fall 2014 - CM Dermatology (11 decks)

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