lab tests Flashcards
1
Q
what population does sensitivity focus on?
A
people who have the disease
2
Q
what population does specificity focus on?
A
people without the disease
3
Q
screening tests have ____ sensitivity and ___ diagnostic threshold
A
high
low
4
Q
screening tests have ____ specificity and ___ diagnostic threshold
A
low
high
5
Q
reference range encompases what percentage of people
A
95%
6
Q
what are the common tests?
A
Urinalysis, urine microscopy, CBC with platelets +/- differential, Chemisteries
7
Q
What are the chemistry tests
A
albumin, alkaline phosphatase, ALT, AST, bilirubin, BUN, calcium, chloride, creatinine, glucose, potassium, sodium
8
Q
what does the therapeutic range measure? what does it screen for?
A
effectiveness of medication, screens for possible toxicity due to medication
9
Q
what is the desirable range
A
prognosis related ranges, associate lab results with clinical outcomes
10
Q
what is the type of test that detects disease in people who have it, but may be false positive in healthy people
A
sensitive test
11
Q
why are some tests sensitive?
A
Want to make sure we aren’t missing someone who has the disease as the consequences may be deadly
12
Q
what is the type of test where healthy people may have a normal/negative result, but may miss the disease in someone who has it
A
specific test
13
Q
positive predictive value focuses on who?
A
people with a positive test result; likelihood that positive test result identifies someone with the disease
14
Q
Negative predictive value focusees on who?
A
people with negative test result; likelihood that negative test result identifies someone without that disease
15
Q
prevalence definition
A
number of existing cases in a population
ex 48% of American adults have HTN
16
Q
incidence definition
A
number of new cases occurring within a period of time
usually one year
ex sore throat (many new cases of sore throat appear every year)
17
Q
questions to ask before ordering test
A
- why is test being ordered
- what are consequences of not ordering the test
- how good is the test in discriminating between health vs disease
- how will test results influence patient management and outcome
18
Q
what phase of lab testing do most errors occur in? what percent of errors?
A
Pre-analytic phase
19
Q
ways to avoid lab pre-analytic errors
A
- ask right questions (when did you last eat/drink? when was your last dose of medication?
- use right samples (test tube, swab type, needle size)
- label sample correctly
- handle and transport sample correctlly
- obtain proper quantity of sample
- order test properly
20
Q
what factors impact test results
A
- biological (age, sex)
- behavioral (smoking, exercise, stress)
- clinicial (diseases, drug therapy, pregnancy)
- specimen collecting and handeling
21
Q
Approaches for establishing diagnosis
A
hypothesis deduction
pattern recognition
rifle vs shotgun approach
22
Q
what is hypothesis deduction
A
use H&P to formulate differential diagnosis, then select labs likely to confirm a diagnosis
23
Q
what is pattern recognition?
A
compare patients pattern for results of several lab tests
medical algorithms (decision trees)
logical and sequential
maximize clinicians efficiency
can minimize ordering unnecessary tests
24
Q
what is rifle vs shotgun approach (try to hit bulls eye)
A
rifle: ordering specific tests based on diagnostic accuracy and predictive value
shotgun: indiscriminately order a large number of tests
25
costs of certain labs
CBC= $51
Lipid panel= $68
Urinalysis= $92
Hgb A1c= $61
TSH= $108
HIV= $92
if you ordered all of these for patient without insurance = $472 (doesnt include cost of visit)
26
Basic urinalysis (dipstick)
color
specific gravity
pH
heme/blood
albumin/protein
urinary glucose
ketones
nitrite
leukocyte esterase
bilirubin
urobilinogen
27
Basic UA- color
normal- pale yellow to amber
straw color- normal but low specific gravity (hydrated)
amber color- normal but high specific gravity (dehydrated)
28
colorless urine clinical applications
common/important
- large fluid intake
- untreated Diabetes mullitus
- diabetes insipidus
- alcohol
other
- reduction of perspiration
-chronic intersitital nephritis
- nervousness
29
orange urine clinical applications
common/important
-dehydrated/restricted fluid intake
- concentrated urine
- fever
- medications (pyridium/AZO)
other
-excessive sweating
-small quantity of bile
-medications- (sulfasalazine -GI)
30
brownish/greenish urine color means what
bilirubin
31
reddish or dark brown color means what
Blood (RBCs)
Hemoglobin
myoglobin
Porphyria (metabolic dz)
meidcation: Cascara/senna (laxitive)
Foods: beets, blackberries, rhubarb
32
milky urine color means what
fat, pus, WBC
33
Purple urine color means what
porphyria
purple urine bag syndrome (cath+infection)
34
what is porphyria
a rare hereditary disease in which the blood pigment hemoglobin is abnormally metabolized.
35
green urine means what
medications
food dyes
36
brown-black urine means what
hemoglobin
lysol poisining
melanin
37
black urine means what
alkaptonuria (metabolic dz)
38
what is normal specific gracity in UA
SG= 1.003-1.035
39
what is SG: 1.025-1.030+ mean?
concentrated urine
40
What does SG: 1.001-1.010 mean?
dilute urine
41
what does SG: 1.001-1.018 mean?
infants <2 years old
42
what can high specific gravity mean?
DM
dehydration
fever
vommiting
diarrhea
increase ADH (antidiuretic hormone)
43
what does low specific gravity mean?
Diabetes inspiidus
decrease ADH
glomerulonephritis
severe renal damage
44
average urine PH range
4.6-8 (6.0)
45
acidic urine can mean what?
uncontrolled DM
ketoacidocis
kidney stones
emphysema
diarrhea
starvation
dehydration
diet high in protein
46
alkaline urine can mean what?
UTI (some bacterial strains)
aspirin intoxication
kidney problems
diet high in fruits and veggies
47
what does fruity and foul urine odor mean?
Diabetes mellitus (Fruity)
Bacteria (foul)
other- metabolic diseases (ex maple syrup urine disease)
48
what is term for blood in urine
hematurina
49
false negative of hematuria is caused by what
vitamin C
50
false positive of hematuria is caused by what
menstrual blood, concentrated urine, vigorous exercise
51
positive urine blood clinical applications
common/important
-lower UTI
Nephrolithiasis
urinary tract cancers
renal cancers
urinary catheter (trauma)
anticoagulants
strenuous exercise
other
hemophilia
lupus
glomerulonephritis
heavy smokers
52
urine protein/albumin is the most important indication of what?
kidney disease (even in an apparently healthy person if persistent)
53
term for increased protein in urine
proteinuria (can be mild, moderate or severe)
54
urine protein/albumin
Normal value: none/negative
various kidney diseases DM
chronic urinary tract obstruction
malignant hypertension
fever
trauma
lupus (can affect kidneys)
poisoning
false negative for protein: numerous WBCs/epithelial cells in sample
55
urinary glucose
normal value: none/negative
kidneys normally reabsorb glucose
Glucosuria or glycosuria= increased urinary glucose
increased:
DM
Pituitary disease/brain injury
Various kidney diseases
Glucose not always abnormal: large meal/emotional stress
positive urine glucose requires evaluation for diabetes
56
Urinary glucose interfering factors
vitamin C- false negative
Ketones- false negative
57
Urinary ketones
normal value: none/negative
ketones are products of FA metabolism
Ketonuria- increased urinary ketones
clinical implications
DM (ketoacidosis)
starvation/fasting
high fat diets
low carb diet
prolonged vomiting
fever
anorexia
pregnancy/lacation
58
urinary ketones false positive causes
dehydration
medications
59
Urinary nitrite
normal value: negative
some bacteria convert nitrate into nitrite
nitrite can be negative during infection if: patient urinating frequently, infection with certain organisms, diet low in nitrates
getting a 1st morning urine is ideal
60
interferring factors with urine nitrite
pyridium/AZO:false positive
Vitamin C: false negative
Contamination: false positive
61
Urine leukocyte esterase
normal value: negative
LE is an enzyme in WBC
62
urine leukocyte esterase clinical implications
UTI
sterile pyuria
+ indicates pyuria, + should be evaluated microscopically (especially if nitrites are also present)
63
causes of false positive leukocyte esterase
vaginal discharge
trichomonas
parasites
contamination
64
causes false negative leukocyte esterase
pyridium/azo
vitamin C
65
urinary bilirubin
normal range: 0-.02mg/dL
clinical implications- trace amounts are abnormal and require further investigation
Interfering factors
Pyridium= false positive
vitamin C= false negative
light exposure cause bilirubin to rapidly decompose
Increased levels: think liver!
Hepatitis
infection or toxic agents
obstructive biliary tract diseases
66
Urine urobilinogen value and clinical applications
normal value= .1 -1.0mg/dL
clinical implications:
increased hemolysis
incrased liver disease
decreased biliary obstruction (gallstones)
decreased antibiotic therapy
67
urine test specimen handling
test within one hour or refridgerate
otherwise- glucose levels drop, ketones dissipate, color deepens, pH more basic (alkaline), bilirubin and urobilinogen may be oxidized
68
urine microscopy- bacteria
20+ bacteria/HPF may mean UTI, if nitrite is positive too= reliable indicator of infection
69
what do WBCs in urine usually indicate
UTi or injury (5 or more per HPF (high power field), timing of test is critical
interfering factors - same as leukocyte esterase (vaginal discharge, trichomonas, parasites, heavy mucous discharge
70
what do RBCs in urine usually indicate and when is it significant
significant if 2 or more RBCs/HPF
UTI
Renal cancer
bladder cancer
kidney stones
71
what does it mean if you see epithelial cells in urine under the microscope?
The presence of squamous epithelia cells indicates contamination of sample (not clean catch)
72
What do red blood cell casts mean when looking at urine under microscope?
Indicate hemmorrhage and always pathologic
-glomerulonephritis
renal infarction
lupus
others
73
what do white blood cell casts mean if you see them in urine microscopy?
Come from kidney tubules, indicate renal parenchymal disease
may indicate
pyelonephritis
glomerulonephritis
another kidney disease
74
urine microscopy-crystals types
Uric acid- acidic urine- normal or kidney stones
Oxalate- acidic urine- normal or kidney stones
Phosphate-ALKALINE urine- normal or kidney stones
Cystine-acidic urine- PATHOLOGIC
crystals are microscopic, stones are visible to eyes
75
which urine microscopy crystal is pathologic?
Cystine
76
bottom line- remember to consider if patient is taking what supplements/medications?
AZO/pyridium and vitamin C
77
bottom line- positive nitrites and positive LE what does this indicate
Thisnk infection (esp if WBCs on micro too)
78
bottom line- blood in urine what do you do?
requires further investigation!
79
Bottom line- protein in urine?
Think kidney disease
80
Bottom line- glucose in urine?
Check for diabetes
81
Bottom line- epithelial cells in urine?
contaminated sample
82
unclotted whole blood has what parts top to bottom?
Plasma (yellow)
buffy coat
Red blood cells
83
Clotted whole blood has what parts top to bottom?
Serum (yellow)
clot
84
what is included in CBC?
WBCs
RBCs
platelets
hemoglobin
hematocrit
performed on whole blood- lavender/purple tube with EDTA that prevents clotting
85
what can alter CBC results? lavendar tube
stress
natural body rhythms
dehydration/overhydration
fat-laden meals may alter
do you need to fast before this? NO not necessary
86
what is normal WBC range?
4000-11000 per microliter
87
what is the term for increased WBCs and decreased WBCs?
leukocytosis and leukopenia
88
what are the 5 types of WBCs
Neutrophils
Eosinophils
Basophils
Monocytes
Lymphocytes
89
Leukocytosis is WBC count above ____?
11000microliters
usually result of increase in just one cell type
90
types of leukocytosis
Neutrophilia
basophilia
eosinophilia
monocytosis
lymphocytosis
91
Causes of Leukopenia?
WBC below 4000 microliters
Causes:viral infections, some bacterial infections, BAD infections (sepsis), meds that suppress bone marrow, bone marrow disorders (leukemia)
92
Neurophils do what for your body?
Primary defense against microbial invasion
PMNs (Polymorphonuclear Leukocytes)
most numerous WBC
93
Neutrophilia important causes
Bacterial infection
inflammation
Nonpathogenic
steroids
94
Neutropenia important causes
overwhelming bacterial infection
viral infection
95
What do lymphocytes do and where are they made and what types are there?
Lymphocytes migrate to areas of inflammation, made in bone marrow and play role in immune response, 3 types are B cells, T cells, and Natural Killer (NK) cells
96
important lymphocytosis cause
Mononeucleosis (viral infection)
97
important lymphopenia causes
chemo and radiation
AIDs
98
What are Eosinophils and what do they contain?
Bilobed nuclei (also Polymorphonuclear Leukocytes)
Contains Granules--> has chemicals toxic to invaders and host cells
eosinophil counts affected by time of day, burns, post surgery
99
Eosinophilia causes
"wheezes, sneezes, and weird diseases"
Allergies, asthma, parasitic tapeworm diseases, medications, eczema
100
Eosinopenia causes
medication and early bacterial infection
101
What are Basophils and what do they have
Granules that obscure the nucleus, produce histamine and other substances
Basophils are PMNs
102
Basophilia causes
allergies (seasonal food drug)
103
Basopenia
acute phase of infection, prolonged steroid therapy
104
monocytes are what
big cells with big nuclei
second line of defense against infection
105
monocytosis causes
infections (TB, parasites, ticks) and recovery
106
Monocytopenia causes
prednisone treatment and HIV infection
107
what cells do not have nuclei?
Red blood cells
108
What do RBCs do
cary oxygen to tissues and bring CO2 back to lungs
use heloglobin to carry/deliver oxygen (need iron!)
lifespan- 120 days
109
RBC count
differs men vs women
men 4.5-6 x 10^6/ml
women 4-5.0x10^6 /ml
110
Erythrocytosis (RBC increase) causes
Polycythemia vera
Renal disease
high altitude
pulmonary disease
cardiovascular disease
tobacco
dehydration
111
Erythropenia (RBC decrease) causes
Anemia
bone marrow/blood cancers
lupus
112
What test differs betweeen men and women in RBC Hgb/Hct (H&H)
Hemoglobin AND Hematocrit differs, Hemoglobin is inital test to check for anemia
113
How much more hematocrit do we have than hemoglobin?
Hct= Hgbx3
114
what are platelets
smallest formed cellular elements, mostly formed in bone marrow and some in spleen
115
what is the role of platelets
blood clotting, vasoconstriction
normal range= 150k-450k
116
what is term for increased and decreased platelets
thrombocytosis
thrombocytopenia
117
what causes thrombocytosis
cancers
acute infections
118
what causes thrombocytopenia
some infections (viruses bacteria)
liver disease (cirrhosis)
119
Basic metabolic panel components
Na+
K+
CL-
HCO3
BUN (blood urea nitrogen)
Creatinine
Serum glucose (blood sugar)
Ca2+
120
what is BMP perofrmed on?
serum (gold tube)- gel helps serum separate from other blood components
or
plasma- light green tube
has heparin (anticoagulent) in it
121
BMP-sodium- where is primary cation?
what is term for increased and decreased sodium?
extracellular fluid
Hypernatremia
Hyponatremia
122
BMP- potassium K+- where is primary cation?
what is term for increased and decreased potassium
intracellular fluid
Hyperkalemia
Hypokalemia
123
what to remember about potasium?
if blood sample is hemolyzed during collection, K+ LEAVES the cells and there is falsely elevated K+ level
124
BMP-Chloride- where is primary anion found?
extracellular fluid
Na+Cl-= BFFs
125
What is term for increased and decreased serum cloride?
Hyperchloremia and hypochloremia
126
BMP-Bicarbonate (HCO3- ,CO2 content) what does it do?
Acts as a buffer when H+ is produced by metabolism of acids
127
what is increased and decreased bicarbonate
alkalosis and acidosis
128
BMP- BUN (blood urea nitrogen) what does it do
protein metabolism
ammonia production
urea synthesizes in the liver
129
Increased BUN caused by what?
Kidney insufficiency
UTI
130
Decreased BUN caused by what?
Low protein diet
Cirrhosis
starvation
131
BMP-Creatinine is made how
muscle metabolizes creatine and produces creatinine
more muscle mass--> more creatinine production
132
What does elevated Creatinine mean
decreased renal function
133
what differs slightly between women and men that is produced by muscles?
creatinine
134
does low or high GFR create a problem?
low GFR= kidneys not working well
135
What is the Anion gap from the BMP?
formula?
Difference between serum cations and anions
formula: anion gap= Na - (Cl+HCO3)
136
What does increased and decreased anion gap mean?
increased= type of acidosis
decreased= rare
137
BMP-serum glucose is used for what?
primary energy source for metabolism
liver converts carbs to glucose
excess glucose converted to glycogen in liver/muscle- process needs insulin
138
increased serum glucose name and what causes it?
hyperglycemia
causes: DM, endocrine disorders, severe infection, steroids
139
decreased serum glucose name and what causes it
hypoglycemia
metabolic disorders, too much insulin medications, liver disease
140
BMP- serum calcium Ca2+ term for increased and what does it cause
hypercalcemia
heart problems
141
BMP-serum calcium Ca2+ term for decreased and what does it cause
hypocalcemia
muscle contactions, seizures
142
what causes increased serum calcium?
hyperparathyroidism (bone breakdown)- releasing calcium
Too much vitamin D
143
what causes decreased serum calcium?
Hypoparathyroidism (bone building)- breaking down calcium to build
vitamin D deficiency
144
Elevated Hemoglobin A1c of 6.5% + is diagnostic of what?
Diabetes mellitus
145
What test is not accurate during pregnancy that diagnoses DM?
Hemoglobin A1c
146
What enzyme is produced by the pancreas faster than lipase?
Serum Amylase
147
what causes increased serum amylase?
pancreatitis
148
what casues decreased serum amylase?
pancreatic insufficency
149
Serum lipase is produced where
pancreas
stays elevated longer in pancreatitis than amylase
150
What causes increased serum lipase?
pancreatitis
151
Serum AST (asparate aminotransferase) is produced where?
Liver
also found in heart, muscle, kidney which gets released when tissues injured
152
increased serum AST causes what
liver problems
153
Where is serum ALT (alanine aminotransferase) produced
Liver
small amounts in muscle and heart- gets released when tissues injured
increased- causes liver damage as well as AST
154
Serum alkaline phosphatase is produced where and present where
Liver
present many types of cells (bone, biliary tract, intestines, placenta, kidneys)
Gets released when cells are destroyed or during growth periods
155
decreased serum alkaline phosphatase causes what
osteoporosis
156
increased serum alkaline phosphatase causes what
liver problems
157
serum bilirubin comes from what?
Breakdown of RBCS
bilirubin conjugated in liver and excreted in bile
158
increased serum bilirubin causes increased breakdown of RBCs (hemolysis)
certain liver and bile duct problems
159
what is CMP
What does it include?
= comprehensive metabolic panel
includes everything in BMP plus
AST
ALRT
Alk Phos
Bilirubin
Total Protein
Albumin
160
what is included in BMP
NA
K
Cl
HCO3- bicarb
BUN
Cr
Glucose
Ca
161
serum GGT (gamma glutamyl transferase) is made where and found where
liver
found in kidney, prostate, spleen
increased= liver problems
162
Point of care testing means what
inexpensive tests
performed at "point of care" (bedside)
performed with non-lab personal
get results faster than non-POCT
speed at expense of accurace
may need further/confirmatory testing
163
