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Foundations of Clinical Medicine > Clinical Laboratory Medicine > Flashcards

Clinical Laboratory Medicine Flashcards

1
Q

What is the purpose of all lab testing?

A

To reduce clinical uncertainty

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2
Q

What % of the population is abnormal but free of disease?

A

5%

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3
Q

What are more likely to cause incorrect results: clerical errors or technical errors?

A

Clerical errors

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4
Q

Define sensitivity.

A

The proportion of people with a disease who have a positive test result.
(If the person has the disease, a highly sensitive test will find it)

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5
Q

When a highly sensitive test provides a negative result, can you rule out the diagnosis?

A

Yes

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6
Q

What is an example of a highly sensitive test?

A

D-dimer
If -, can rule out pulmonary embolus
If +, cannot rule in the diagnosis

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7
Q

Define specificity.

A

The proportion of people without disease who have a negative result.

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8
Q

If a highly specific test provides a positive result, can you rule in the diagnosis?

A

Yes

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9
Q

What tests are included in a CBC?

A 
RBC
Hgb
Hct
WBC
MCV
MCH
MCHC
RDW
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10
Q

If collecting a CBC with differential, what information is added?

A 
Neutrophils
Bands/Segs
Lymphocytes
Monocytes
Eosinophils granulocytes
Basophils granulocytes
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11
Q

What would elevated neutrophils indicate?

A

Bacterial infection

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12
Q

What would elevated bands/segs indicate?

A

An active infection (shift to the left)

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13
Q

What would elevated lymphocytes indicate?

A

Viral infection

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14
Q

What would elevated eosinophil granulocytes indicate?

A

Allergic/hypersensitivity reactions

Parasitic infections

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15
Q

What is the normal range for WBCs?

A

4000-10,800

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16
Q

What is the normal range for Hgb?

A

14-18 g/dL men 13&up

12-16 g/dL women 13&up

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17
Q

What is the normal range for Hct?

A

42-54% men 13&up

36-48% women 13&up

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18
Q

What is the normal range for Plt?

A

140,000-400,000

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19
Q

What tests are included in a Chem 7?

A 
Na+
K+
Cl-
HCO3
BUN
Creatinine
Glucose
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20
Q

When would you want to test glucose levels?

A

To diagnose diabetes, hypoglycemia

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21
Q

When would you want to test Na+ levels?

A

To diagnose dehydration and overhydration

To evaluate water balance

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22
Q

When would you want to test K+ levels?

A

To diagnose hyper/hypokalemia

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23
Q

When would you want to test Cl- levels?

A

To assess electrolyte, acid-base, and water balance along with Na+, K+, and CO2

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24
Q

When would you want to test HCO3?

A

To assess acid-base balance

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25
Q

When would you want to test BUN?

A

To assess renal function since it is cleared by the kidneys

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26
Q

When would you want to test Creatinine?

A

To assess renal function since it is cleared by the kidneys

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27
Q

What are other instances that would elevate BUN besides renal insufficiency?

A

Dehydration

Upper GI bleeds

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28
Q

What is the normal BUN/creatinine ratio?

A

10:1

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29
Q

What would a BUN/creatinine ratio of >20:1 indicate?

A

A pre-renal issue

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30
Q

What would a BUN/creatinine ratio of <10:1 indicate?

A

A renal issue

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31
Q

What tests are included in a coag panel?

A 
Partial Thromboplastin Time (PTT)
Prothrombin Time (PT) / INR
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32
Q

When would you order a PTT?

A

To monitor heparin therapy’s effect on the intrinsic pathway (factors I, II, V, VIII, IX, X, XI, XII)

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33
Q

When would you order a PT/INR?

A

To monitor Coumadin therapy’s effect on the extrinsic pathway (factors I, II, V, VII, X)

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34
Q

What information can you get from a macroscopic urinalysis?

A

Color (pale-dark yellow normal)

Turbidity (clear is normal)

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35
Q

What information can you get from a dipstick chemical analysis?

A 
pH
Specific gravity
Protein
Glucose
Ketones
Nitrite
Leukocyte esterase
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36
Q

What is normal pH of urine?

A

4.5-8.0

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37
Q

What is normal specific gravity of urine?

A

1.022-1.035

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38
Q

What does a specific gravity of <1.022 after 12 hours without food or water indicate?

A

Renal concentrating ability is impaired

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39
Q

What does a specific gravity of >1.035 indicate?

A

May contain high levels of glucose

Pt may have recently had IV dye

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40
Q

What is normal protein of urine?

A

<150mg/24 hours

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41
Q

What does protein of >3.5grams/24 hours indicate?

A

Nephrotic syndrome

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42
Q

What is the indicator dye used for protein detection?

A

Bromphenol blue

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43
Q

How much filtered glucose appears in the urine?

A

<0.1%

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44
Q

What does glucosuria indicate?

A

Diabetes mellitus

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45
Q

What do ketones in the urine indicate?

A

Breakdown of protiens
Diabetic ketosis
Calorie deprivation

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46
Q

What do nitrites in the urine indicate?

A

Bacteria in the urine, usually from gram negative rods

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47
Q

What does leukocyte esterase in the urine indicate?

A

Presence of WBCs

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48
Q

What needs to be ordered following a positive nitrite test?

A

24 hour urine for protein

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49
Q

What needs to be ordered following a positive leukocyte esterase test?

A

Microscopic evaluation with culture

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50
Q

What can be seen in a low power field (lpf) microscopic urinalysis?

A

Crystals
Casts
Squamous cells

51
Q

What can be seen in a high power field (hpf) microscopic urinalysis?

A

Crystals
Cells
Bacteria

52
Q

What is an abnormal amount of RBCs in the urine?

A

> 1 RBC/hpf

53
Q

What could cause hematuria?

A 
Glomerular damage
Tumors
Kidney trauma
Kidney stones
UTI
Menstruation
54
Q

What do you know about the concentration of urine if RBCs appear swollen?

A

Urine is dilute

55
Q

What do you know about the concentration of urine if RBCs appear cratered?

A

Urine is concentrated

56
Q

What could dysmorphic RBCs indicate?

A

Glomerular disease

57
Q

What is pyuria, and what does it usually indicate?

A

WBCs in the urine

upper/lower UTI or acute glomerulonephritis

58
Q

What is an abnormal number of WBCs in the urine?

A

> 2 WBCs/hpf

59
Q

What does elevated epithelial cells int he urine indicate?

A

Nephrotic syndrome or tubular degeneration

60
Q

What could squamous epithelial cells indicate?

A

Contamination

61
Q

What creates casts, and where are they formed?

A

Protein denaturation and precipitation

In the distal tubule or collecting duct

62
Q

What are some factors that favor cast formation?

A

Low flow rate
High salt concentration
Low pH

63
Q

When are hyaline casts seen?

A

In healthy patients

64
Q

What do RBC casts indicate?

A

Glomerulonephritis

Severe tubular damage

65
Q

What do WBC casts indicate?

A

Acute pyelonephritis

Glomerulonephritis

66
Q

What is a granular cast?

A

A cellular cast that remained in the nephron for some time before it was flushed out

67
Q

When are broad casts seen, and where do they come from?

A

In end stage renal disease

They come from damaged and dilated tubules

68
Q

What is the most common type of yeast seen in routine labs?

A

Candida

69
Q

What types of crystals can be seen even in healthy people?

A

Calcium oxalate
Triple phosphate
Amorphous phosphates

70
Q

How quickly does a clean-catch urine specimen need to be evaluated?

A

Within 1 hour of collection

71
Q

What will happen to the specimen as time elapses prior to evaluation?

A 
Decreased clarity
Increase in pH
Loss of ketone bodies
Dissolution of cells and casts
Overgrowth of contaminating microorganisms
72
Q

When are cardiac enzymes released into the blood?

A

After necrosis of myocardial cells

73
Q

When does troponin begin to rise?

A

2-6 hours after injury

74
Q

Is troponin sensitive or specific for cardiac injury?

A

Specific

75
Q

How long does TnI stay elevated?

A

5-10 days

76
Q

How long does TnT stay elevated?

A

5-14 days

77
Q

What are the 3 kinds of creatine kinase?

A

CK-MB (myocardium)
CK-MM (skeletal muscle)
CK-BB (brain)

78
Q

What causes elevated CK levels?

A 
MI
Trauma
Physical exertion
Post-op state
Convulsions
79
Q

When does CK rise?

A

4-6 hours after injury

80
Q

After how long does CK return to normal?

A

3-4 days

81
Q

If CK-MB is elevated, but not CK-MM or CK-BB, what is probably the cause?

A

Heart injury (MI)

82
Q

If CK-MM or CK-BB is elevated but not CK-MB, what is probably the cause?

A

A non-heart related issue

83
Q

How does CK-MB differ from -MM and -BB?

A

Rises in 4-6 hours and returns to normal in 2 days

84
Q

What causes the release of myoglobin?

A

Injury to striated muscle in skeletal or cardiac muscle

85
Q

When does myoglobin rise?

A

2 hours after MI

86
Q

When does myoglobin peak?

A

6-8 hours after MI

87
Q

What can cause false myoglobin positives?

A

Skeletal muscle injury

Renal failure

88
Q

What tests are included in a lipid panel?

A

Total cholesterol
Triglycerides (LDL, VLDL)
HDL
LDL

89
Q

Why would you order a lipid panel?

A

To monitor risk for CAD

90
Q

When are triglyceride levels the lowest?

A

In the morning

91
Q

What is optimal for triglycerides?

A

<150

92
Q

What can affect triglyceride test results?

A

What the patient ate the day before

93
Q

What is optimal for HDL levels?

A

> 32 mg/dL in men

>38 mg/dL in women

94
Q

What is optimal for LDL levels according to ATP III?

A

<100 mg/dL

95
Q

What is desirable for total cholesterol levels according to ATP III?

A

<200 mg/dL

96
Q

What tests are included in the Arterial Blood Gases respiratory labs?

A 
pH
PO2
PCO2
HCO3-
SaO2
97
Q

Why would you order ABGs?

A

To obtain information on respiration and kidney function

98
Q

What is normal pH in the human body?

A

7.35-7.45

99
Q

What type of compensation is occurring if the unaffected system is attempting to compensate but pH is not within normal range?

A

Partial compensation

100
Q

What type of compensation is occurring when the unaffected system compensates to a nearly normal pH?

A

Complete compensation

101
Q

What is normal PO2?

A

Newborn: 40-70 mmHg
Child/Adult: 80-100 mmHg
Age 60-90: 60-80 mmHg

102
Q

What levels represent the respiratory component?

A

PCO2

103
Q

What is normal PCO2?

A

35-45 mmHg

104
Q

What levels represent the metabolic component?

A

HCO3-

105
Q

What is normal HCO3-?

A

22-28 mEq/L

106
Q

What is normal SaO2?

A

> 90%

107
Q

What can cause inaccurate SaO2?

A

Dyshemoglobinemias

108
Q

What is carboxyhemoglobin?

A

CO bound to hemoglobin

CO has 200 times the affinity for hemoglobin than does O2

109
Q

What PO2 indicates hypoxia?

A

<60 mmHg

110
Q

What PCO2 indicates alkalosis?

A

<35 mmHg

111
Q

What PCO2 indicates acidosis?

A

> 45 mmHg

112
Q

What HCO3- indicates acidosis?

A

<22 mEq/L

113
Q

What HCO3- indicates alkalosis?

A

> 28 mEq/L

114
Q

What tests are included in a sputum evaluation?

A

Gram stain
Bacterial culture
Acid-fast culture (for TB)

115
Q

What would a sputum evaluation show if the patient provided a spit sample instead of sputum?

A

A lot of squamous epithelium

116
Q

Describe characteristics of transudative effusion and what causes it.

A

Watery solution due to increased hydrostatic pressure or low oncotic pressure in the capillaries

117
Q

Describe characteristics of exudative effusion

A

Fluid rich in protein and cellular elements that oozes out of vessels due to inflammation and permits passage of large molecules and solid matter through vessel walls

118
Q

What specific gravity, protein, and PF/serum ratio indicate transudate effusion?

A

SG <0.5

119
Q

What specific gravity, protein, and PF/serum ratio indicate exudate effusion?

A

SG >1.016
Protein >3.0
PF/serum >0.5

120
Q

What WBC, RBC, and glucose indicate transudate effusion?

A

WBC <1000
RBC Few
Glucose = to serum

121
Q

What WBC, RBC, and glucose indicate exudate effusion?

A

WBC >1000
RBC Variable
Glucose <serum

122
Q

What cholesterol, pH, and appearance of urine indicate transudate effusion?

A

Cholesterol <55
pH 7.4-7.5
Clear

123
Q

What cholesterol, pH, and appearance of urine indicate exudate effusion?

A

Cholesterol >55
pH 7.35-7.45
Cloudy

124
Q

If cytology or amylase come back positive, what can you conclude?

A

Malignancy

Pancreatic (+ amylase)

Foundations of Clinical Medicine (5 decks)

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