Clinical Laboratory Medicine Flashcards
1
Q
What is the purpose of all lab testing?
A
To reduce clinical uncertainty
2
Q
What % of the population is abnormal but free of disease?
A
5%
3
Q
What are more likely to cause incorrect results: clerical errors or technical errors?
A
Clerical errors
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)
5
Q
When a highly sensitive test provides a negative result, can you rule out the diagnosis?
A
Yes
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
7
Q
Define specificity.
A
The proportion of people without disease who have a negative result.
8
Q
If a highly specific test provides a positive result, can you rule in the diagnosis?
A
Yes
9
Q
What tests are included in a CBC?
A
RBC Hgb Hct WBC MCV MCH MCHC RDW
10
Q
If collecting a CBC with differential, what information is added?
A
Neutrophils Bands/Segs Lymphocytes Monocytes Eosinophils granulocytes Basophils granulocytes
11
Q
What would elevated neutrophils indicate?
A
Bacterial infection
12
Q
What would elevated bands/segs indicate?
A
An active infection (shift to the left)
13
Q
What would elevated lymphocytes indicate?
A
Viral infection
14
Q
What would elevated eosinophil granulocytes indicate?
A
Allergic/hypersensitivity reactions
Parasitic infections
15
Q
What is the normal range for WBCs?
A
4000-10,800
16
Q
What is the normal range for Hgb?
A
14-18 g/dL men 13&up
12-16 g/dL women 13&up
17
Q
What is the normal range for Hct?
A
42-54% men 13&up
36-48% women 13&up
18
Q
What is the normal range for Plt?
A
140,000-400,000
19
Q
What tests are included in a Chem 7?
A
Na+ K+ Cl- HCO3 BUN Creatinine Glucose
20
Q
When would you want to test glucose levels?
A
To diagnose diabetes, hypoglycemia
21
Q
When would you want to test Na+ levels?
A
To diagnose dehydration and overhydration
To evaluate water balance
22
Q
When would you want to test K+ levels?
A
To diagnose hyper/hypokalemia
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
24
Q
When would you want to test HCO3?
A
To assess acid-base balance
25
When would you want to test BUN?
To assess renal function since it is cleared by the kidneys
26
When would you want to test Creatinine?
To assess renal function since it is cleared by the kidneys
27
What are other instances that would elevate BUN besides renal insufficiency?
Dehydration
| Upper GI bleeds
28
What is the normal BUN/creatinine ratio?
10:1
29
What would a BUN/creatinine ratio of >20:1 indicate?
A pre-renal issue
30
What would a BUN/creatinine ratio of <10:1 indicate?
A renal issue
31
What tests are included in a coag panel?
```
Partial Thromboplastin Time (PTT)
Prothrombin Time (PT) / INR
```
32
When would you order a PTT?
To monitor heparin therapy's effect on the intrinsic pathway (factors I, II, V, VIII, IX, X, XI, XII)
33
When would you order a PT/INR?
To monitor Coumadin therapy's effect on the extrinsic pathway (factors I, II, V, VII, X)
34
What information can you get from a macroscopic urinalysis?
Color (pale-dark yellow normal)
| Turbidity (clear is normal)
35
What information can you get from a dipstick chemical analysis?
```
pH
Specific gravity
Protein
Glucose
Ketones
Nitrite
Leukocyte esterase
```
36
What is normal pH of urine?
4.5-8.0
37
What is normal specific gravity of urine?
1.022-1.035
38
What does a specific gravity of <1.022 after 12 hours without food or water indicate?
Renal concentrating ability is impaired
39
What does a specific gravity of >1.035 indicate?
May contain high levels of glucose
| Pt may have recently had IV dye
40
What is normal protein of urine?
<150mg/24 hours
41
What does protein of >3.5grams/24 hours indicate?
Nephrotic syndrome
42
What is the indicator dye used for protein detection?
Bromphenol blue
43
How much filtered glucose appears in the urine?
<0.1%
44
What does glucosuria indicate?
Diabetes mellitus
45
What do ketones in the urine indicate?
Breakdown of protiens
Diabetic ketosis
Calorie deprivation
46
What do nitrites in the urine indicate?
Bacteria in the urine, usually from gram negative rods
47
What does leukocyte esterase in the urine indicate?
Presence of WBCs
48
What needs to be ordered following a positive nitrite test?
24 hour urine for protein
49
What needs to be ordered following a positive leukocyte esterase test?
Microscopic evaluation with culture
50
What can be seen in a low power field (lpf) microscopic urinalysis?
Crystals
Casts
Squamous cells
51
What can be seen in a high power field (hpf) microscopic urinalysis?
Crystals
Cells
Bacteria
52
What is an abnormal amount of RBCs in the urine?
>1 RBC/hpf
53
What could cause hematuria?
```
Glomerular damage
Tumors
Kidney trauma
Kidney stones
UTI
Menstruation
```
54
What do you know about the concentration of urine if RBCs appear swollen?
Urine is dilute
55
What do you know about the concentration of urine if RBCs appear cratered?
Urine is concentrated
56
What could dysmorphic RBCs indicate?
Glomerular disease
57
What is pyuria, and what does it usually indicate?
WBCs in the urine
| upper/lower UTI or acute glomerulonephritis
58
What is an abnormal number of WBCs in the urine?
>2 WBCs/hpf
59
What does elevated epithelial cells int he urine indicate?
Nephrotic syndrome or tubular degeneration
60
What could squamous epithelial cells indicate?
Contamination
61
What creates casts, and where are they formed?
Protein denaturation and precipitation
| In the distal tubule or collecting duct
62
What are some factors that favor cast formation?
Low flow rate
High salt concentration
Low pH
63
When are hyaline casts seen?
In healthy patients
64
What do RBC casts indicate?
Glomerulonephritis
| Severe tubular damage
65
What do WBC casts indicate?
Acute pyelonephritis
| Glomerulonephritis
66
What is a granular cast?
A cellular cast that remained in the nephron for some time before it was flushed out
67
When are broad casts seen, and where do they come from?
In end stage renal disease
| They come from damaged and dilated tubules
68
What is the most common type of yeast seen in routine labs?
Candida
69
What types of crystals can be seen even in healthy people?
Calcium oxalate
Triple phosphate
Amorphous phosphates
70
How quickly does a clean-catch urine specimen need to be evaluated?
Within 1 hour of collection
71
What will happen to the specimen as time elapses prior to evaluation?
```
Decreased clarity
Increase in pH
Loss of ketone bodies
Dissolution of cells and casts
Overgrowth of contaminating microorganisms
```
72
When are cardiac enzymes released into the blood?
After necrosis of myocardial cells
73
When does troponin begin to rise?
2-6 hours after injury
74
Is troponin sensitive or specific for cardiac injury?
Specific
75
How long does TnI stay elevated?
5-10 days
76
How long does TnT stay elevated?
5-14 days
77
What are the 3 kinds of creatine kinase?
CK-MB (myocardium)
CK-MM (skeletal muscle)
CK-BB (brain)
78
What causes elevated CK levels?
```
MI
Trauma
Physical exertion
Post-op state
Convulsions
```
79
When does CK rise?
4-6 hours after injury
80
After how long does CK return to normal?
3-4 days
81
If CK-MB is elevated, but not CK-MM or CK-BB, what is probably the cause?
Heart injury (MI)
82
If CK-MM or CK-BB is elevated but not CK-MB, what is probably the cause?
A non-heart related issue
83
How does CK-MB differ from -MM and -BB?
Rises in 4-6 hours and returns to normal in 2 days
84
What causes the release of myoglobin?
Injury to striated muscle in skeletal or cardiac muscle
85
When does myoglobin rise?
2 hours after MI
86
When does myoglobin peak?
6-8 hours after MI
87
What can cause false myoglobin positives?
Skeletal muscle injury
| Renal failure
88
What tests are included in a lipid panel?
Total cholesterol
Triglycerides (LDL, VLDL)
HDL
LDL
89
Why would you order a lipid panel?
To monitor risk for CAD
90
When are triglyceride levels the lowest?
In the morning
91
What is optimal for triglycerides?
<150
92
What can affect triglyceride test results?
What the patient ate the day before
93
What is optimal for HDL levels?
>32 mg/dL in men
| >38 mg/dL in women
94
What is optimal for LDL levels according to ATP III?
<100 mg/dL
95
What is desirable for total cholesterol levels according to ATP III?
<200 mg/dL
96
What tests are included in the Arterial Blood Gases respiratory labs?
```
pH
PO2
PCO2
HCO3-
SaO2
```
97
Why would you order ABGs?
To obtain information on respiration and kidney function
98
What is normal pH in the human body?
7.35-7.45
99
What type of compensation is occurring if the unaffected system is attempting to compensate but pH is not within normal range?
Partial compensation
100
What type of compensation is occurring when the unaffected system compensates to a nearly normal pH?
Complete compensation
101
What is normal PO2?
Newborn: 40-70 mmHg
Child/Adult: 80-100 mmHg
Age 60-90: 60-80 mmHg
102
What levels represent the respiratory component?
PCO2
103
What is normal PCO2?
35-45 mmHg
104
What levels represent the metabolic component?
HCO3-
105
What is normal HCO3-?
22-28 mEq/L
106
What is normal SaO2?
>90%
107
What can cause inaccurate SaO2?
Dyshemoglobinemias
108
What is carboxyhemoglobin?
CO bound to hemoglobin
| CO has 200 times the affinity for hemoglobin than does O2
109
What PO2 indicates hypoxia?
<60 mmHg
110
What PCO2 indicates alkalosis?
<35 mmHg
111
What PCO2 indicates acidosis?
>45 mmHg
112
What HCO3- indicates acidosis?
<22 mEq/L
113
What HCO3- indicates alkalosis?
>28 mEq/L
114
What tests are included in a sputum evaluation?
Gram stain
Bacterial culture
Acid-fast culture (for TB)
115
What would a sputum evaluation show if the patient provided a spit sample instead of sputum?
A lot of squamous epithelium
116
Describe characteristics of transudative effusion and what causes it.
Watery solution due to increased hydrostatic pressure or low oncotic pressure in the capillaries
117
Describe characteristics of exudative effusion
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
What specific gravity, protein, and PF/serum ratio indicate transudate effusion?
SG <0.5
119
What specific gravity, protein, and PF/serum ratio indicate exudate effusion?
SG >1.016
Protein >3.0
PF/serum >0.5
120
What WBC, RBC, and glucose indicate transudate effusion?
WBC <1000
RBC Few
Glucose = to serum
121
What WBC, RBC, and glucose indicate exudate effusion?
WBC >1000
RBC Variable
Glucose
122
What cholesterol, pH, and appearance of urine indicate transudate effusion?
Cholesterol <55
pH 7.4-7.5
Clear
123
What cholesterol, pH, and appearance of urine indicate exudate effusion?
Cholesterol >55
pH 7.35-7.45
Cloudy
124
If cytology or amylase come back positive, what can you conclude?
Malignancy
| Pancreatic (+ amylase)
