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91 Cards in this Set
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- Back
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whats a CAC, would we do one in an asymptomatic man w/only risk factor of family hx
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coronary artery calcium: CT to see Ca deposits in coronary a. it asses risk of cardiac disease. test can be dont to confirm dx, monitor, determine prognosis, or screen
**for a man w/o sx we would NOT do this test. it does him no good and can cause free radical damage (from radiation) that will harm him |
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what are 4 reasons we order tests
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1. Screen a disease (general pop or high risk pop)
2. Dx in pt with sx 3. Monitor/Manage therapy 4. Establish prognosis |
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for the pt who works nights and cares for children in daytime and is tired what tests do we order?
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1. CBC to rule out:
-anemia -infection -autoimmune 2. Electrolytes to rule out: -adrenal cortical deficit 3. BUN, creatinite, ALT/AST, sugar levels. TSH **each test should be able to rule in or out the ddx of fatigue that includes: -situational (lack of sleep) -anemia -depression/anxiety -Thyroid Disorder (hyper or hypo) -infection (mono) -Autoimmunity/Hypersensitivity- SLE (lupus) -nutrition -Pregnant -DM- sugar -Adrenal Insufficiency- electrolytes -Cancer -Liver -Renal |
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how can we use labs effectively
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1. do a hx an physical to get ddx
2. develop a ddx 3. Order appropriate test- targeted tests not all of them! 4. Determine if you need more test |
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what can cause you to misintrepret a lab
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1. physiological variation
2. over intrepreteation of results 3. you dont know about the test and cant relate it to clinical findings |
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whats Oslers Rule
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if pt is under 50 find ONE CAUSE of all abnormal results
**never rely on one single value **look for trends **dont ignore abnormal labs |
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what things can alter the reliability of a test
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1. Collection method, comtamination
2. Lab errors 3. Post analytical |
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how can time affect lab values
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cortisol is released in a dinural rhythem
tests with meals can affect levels- fasting glucose dose of drugs nad timing of drugs that were taken |
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how does tobacco use affect labs
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1. increased glucose and catecholamines, cortisol, FFA
2. increased WBC 3. Increased CEA- cancer marker 4. increased CO 5. Increasd Hg |
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what does Etoh do to labs
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increased triglycerides
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what does ceffeine do to labs
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increased catecholamines
increased glucose increased lipids with chronic consumption |
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what are some non pathological variables that alter labs
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1. age
2. sex 3. preggers 4. exercise/traning 5. Posture (renin levels) |
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what happens to labs in old folks
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1. decreased albumin
2. lower mm mass so lower creatinine adn other mm related enzymes 3. Decreased lymphocytes |
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what happens to a kids labs
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they have WAY mroe lymphocytes, abnormal needs to be >2500/mm3
normal adult is more than 1500 mm3 **alkaline phosphatase is higher bc they are growing |
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if alkaline phosphatase is elevatedin a kid what does it mean
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it means they are growing. benign
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when are there more differences seen in labs btwn men and women
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puberty
**gender specific hormones like estrogen **estrogen lowers Hg, ferratin, Fe. but at menopause when decreased estrogen we get more male like patterns **smaller mm mass so: decreased creatinine, BUN, AST, CK, |
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how can being in great shape alter labs
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1. Increased mm enzymes due to strenous activity (increaed baseline)
2. lactic acid increased 3. lower MCH (mean cell hemoglobin), lower glucose, lower WBC (bc they lyse) 4. Higher Bilirubin and BUN |
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how are lab "normals" found
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based on gaussian distribution includes 95% of pop (mean +- 2SD from mean) 5% of pop will be normal but will be seen as abnormal
**each test and each lab determine reference themselves |
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if you do a million independent lab tests is it likely you will get an abnormal
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yep!
and it can be an abnormal that isnt associated with disease (recall 5% of pop is normal but not counted that way) |
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what is...
1. Accuracy 2, Gold Standard 3. Prescision 4. Prevalence 5. Incidence |
1. Accuracy- reliability of a test
2. wht you compare new tests to 3. reproducibity of a certain result (may not be accurate) 4. number of pts with disease in a group thats tested 5. how many ppl get it in a eyar |
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what tells us....
1. the best test, all otehrs are measured against this 2. reproducibility of a result 3. reliability of rest method/result 4. frequency of disease in a pop 5. number of pts who get a disease in a year |
1. gold standard
2. Prescision 3. accuracy 4. incidence |
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ok so whats
TP (true positive) TN (true negative) FP (false positive) FN (false negative) |
TP: + test and has disease
TN: - test and doesnt have disease **for the FP and FN the +/- refers to teh TEST RESULT FP: tested + but dont have disease FN: tested - but have the disease |
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what is it called when a pt with a disease gets a - test result?
what is it called when a pt w/o a disease gets a positive test |
False negative
False Positive **the + and - refers to the test result |
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what is sensitivity
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number of ppl with a positive test that HAVE the disease
TP/TP + FN **we want all of the ppl with the disease |
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what is this?
TP/TP + FN |
sensitivity
**its the number of ppl who tested + out of the total number of ppl with disease |
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what determinant cares about how many ppl have the disease
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sensitivity
TP/TP + FN TP + FN = total numebr of ppl with disease |
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what is the specificity
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number of ppl with a negative result who dont have disease
TN/TN + FP |
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what is the numebr of ppl with a negative test who dont have the disease
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specificity
TN/TN + FP |
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what is TN/TN + FP
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specificity
**number of ppl with a negative test who doent have disease |
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what tells us the f that a positive result is correlated with acutally having disease
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PPV
TP/TP + FP |
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what is TP/TP + TN
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PPV, positive predictive value
**the frequency a positive test correlated to a pt that has the disease |
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what is PPV
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positive predictive value. the frequency a positive test result correlated with the pt having the disease
TP/TP + FP |
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what is NPV
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the % of all neg tests that are truely negative
TN/TN + FN |
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what is the percent of all negative test results really being negative
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NPV
TN/TN+FN |
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what is TN/TN+FN
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NPV
**percent of negative test results being truely negative |
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when we set up a test do we want it to be sensitive and specific
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not really, we want one or the other
**more sensitive means less specific |
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what value increases as the prevalence of a disease decreased
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increase the numebr of false positives
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why would we care about a negative test
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if we get a negative we can rejuct that disease as a dx
**good with sensitve tests with a neg result??? dbl check this |
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does specificity or sensitivity deal with the ppl who DONT have disease
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specificity
TN/TN + FP **all of the ppl with disease |
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what parameters deal with the PEOPLE
what parameters deal with the TEST |
PEOPLE: specificity, sensitivity
TEST: PPV, NPV |
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BUN
made? excreted? increased? |
made in liver from breakdown of AA derived ammonia
renal excretion **increased in almost all renal disease and poor renal perfusion (poor perfusion can be due to: dehydration, shock, heart failure) |
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why might BUN be elevated
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made in liver, renal excretion
*increased in renal disease *increased with poor renal perfusion: dehydration, shock, heart failure *huge increase with GI bleed *increased with catabolic state like DM, fever, burn, exercise **decerased in vegans and end stage liver failure |
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what is creatine
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production is proportional to mm mass
renal excretion- measures glomerular filtration rate (GFR) *increased with most renal disease *not very sensitive but specific for renal disease |
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what can BUN and creatine tell us about renal health
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BUN- sensitive for decreased glomerular filtration
Creatine- specific for renal impairment (not sensitive) indirect measure of glomerular filtration rate |
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when is creatine elevated
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in most renal disease
-late renal disease -poor renal perfusion -dehydration **insensitive but specific for renal impairment |
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what is biliruben
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from Hg degradation
*tissue accumulation of biliruben is called jaundice Prehepatic: hemolysis Intrahepatic: liver disease, hematitis, cirrhosis Post Hepatic: gallstone in bile duct |
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what can cause pre, intra, and post hepatic jaundice
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buildup of biliruben
Pre- hemolysis Intra: liver disease like hepatitis or cirrhosis Post: gallstone in bile duct **biliruben is production of the breakdown of Hg |
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what can enzymes in labs tell us
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released from certain tissues when cells lyse
**tells us where tissue maybe injured |
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where is alkaline phosphatase
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Liver- biliary system
Bone- osteoblasts Placenta- increased when preg Intestine (genetic) Cancer makes it **increased in kids who grow |
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what is lactate dehydrogenase
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non specific indicator of necrosis
**small increase relates to small tissue damage **HIGH means hemolysis (RBC lysis), platelet degradation |
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if we have hemolysis wht might be elevated
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LD (lactate dehydrogenase really high)
Prehepatic biliruben |
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what is a non specific indicator of necrosis
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LD (lactate dehydrogenase)
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what is the liver specific? AST ALT
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ALT is more liver specific
AST is also increased in cardiac/sk mm injury |
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what are the sources of AST ALT
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AST: liver, cardiac mm, sk mm
ALT: liver only |
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what labs indicate MI
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1. Troponin I/T- cardiac specific
2. CK-MB 3. AST- non specific 4. LD- non specific 5. Myoglobin |
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what does it mean if ALT is normal and AST is high
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it means its not hte liver
**can be cardiac or sk mm injury also with AST |
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what are the liver labs?
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1. ALT (and also AST)
2. Alk Phosphatase 3. Bilirubin 4. Albumin (low) 5. LD 6. GGT (gamma glutamyl transferase) |
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whats going on?
increased ALT AST increased ALP (Alk Phos) increased GGT imncread LD decreased ALbumin |
liver problem
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what are the libs for sk mm
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1. CK
2. AST 3. LD 4. Aldolase 5. Myoglobin |
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what enzyme is involved in bone disease
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alk phos
**normal to be elevated in growing kids |
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whats the problem
increased CK, AST, LD, Aldolase, myoglobin |
sk mm injury
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what are the 2 main categories of plasma proteins
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1,. albumin
2. globulins (everything else) alpha, beta, gamma globulins. made by plasma cells |
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what is the source of plasma proteins
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1. Albumin- liver (major contributor)
2. Globulins- Plasma cells |
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what shoudl we do with increased globulins
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order more tests!
protein electrophoresis plus immunofixation. this will tell us what Ig is elevated *can be a plasma cell malignancy |
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what does prealbumin give us info about
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1. malnutrition
2. alterations in liver fx **binding protein for thyroxine, vit A, short (2day) half life. **aka transthyretin |
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what lab assessed nutrition
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prealbumin
**sensitive indicator of nutrition as well as alterations in liver fx |
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what will cause decreased albumin
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1. Decreased Synthesis
-malabsorption/malnutrition (prolonged) -chronic inflammation -hepatic dysfunction 2. Increased Loss - renal disease (nephrotic syndrome) -Protein losing gastroenteropathy -acites |
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is increased albumin common
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not really, seen in dehydration or as an artifact if the tourniquit is on for too long
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whts albumin good for?
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oncotic pressure
**its the main part of plasma proteins *it carries things * long half life *commonly decreased but increase is rare (seen in dehydration/tourniquit on for too long) |
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waht is the major alpha 1 globulin? when is it high? when is it low
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a 1 antitrypsin
protease inhibitor acute phase reactant *8deficic causes pulm emphysema and cirrhosis (milfolded protein) |
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what is a-1-antitrypsin
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its the major a 1 globuilin
**it is a protease inhibitor **its an acute phase reactant **a defecit will cause Pulm emphysema or cirrhosis |
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what is an a 2 globulin
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increased in acute inflammation
**ex a 2 macroglobulin (kinin inhibitor) ** ex haptoglobin (carries free hg) ** ex CRP (sensitive indicator of necrosis, acute infection, inflammatin) |
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what does CRP do
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its an a 2 globulin that is increased in:
- necrosis - acute infection -inflammation |
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CRP gives predictive value for what
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cardiovascular thigns like
MI, stroke **its an acute phase reactant **crp coats bugs and acts as opsonin |
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what are the acute phase reactants (objective)
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1. Neutrophiliia
2. Thrombocytosis (increased platelets) 3. Fibrinogen increased 4. a-2-maculoglobulin increased (kinin inhibitor) 5. CRP increased 6. haptoglobin (increased, carried free Hg) 7. Albumin decreased (stop making this so we can make otehrs) 8. ERS increased **all of these increase with acute phase reactions and are caused by an icnrease in TNF1/IL1 |
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tell me about ESR
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length a RBC falls in a given time
**the time is influenced by all of the charges in the tube. RBC are - so repel. In acute inflammation (acute phase reactants) we have increased globulins and decreased albumin so sedimentation is higher **increased ESR is non specific indicator of inflammatino |
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what is a non specific indicator if inflammation
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increased ESR
**seen when globulins are increased and albumin is decreased (as in acute ohase reactants) |
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when is ESR increased
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acute inflammation (acute phase reactants) non specific indicator
**increased globulins and decreased albumin lead to increased sedimintation |
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what are some of the b globulins
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1. beta lipoprotein
2. transferin- transports Fe 3. Complimant C3 4. Fibrinogen |
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how are gamma globulins made
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PLASMA cells
IgG, IgM, IgD, IgE, IgA Decreased gamma globulin menas there is a B cell deficit **i think plasma only make gamma globulin, not the others |
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what does it mean when there si a decrease in gamma globulin
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g globulin is made by plasma cells (IgG, IgM, IgD, IgA, IgE)
When these are low it menas there is a B cell defect |
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what is teh source of plasma proteins
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Albumin- liver
Globulins- most from liver, gamma globulin from plasma cells |
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waht is gammopathy
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increased Ig (gamma globbulin from plasma cells- increased plasma protein conc)
**g globulin isnt an acute phase thing, it take time adn the adaptive immune system to make AB (Ig) Increases can be: 1. Polycolnal- autoimmune disease, chronic infections 2. Monoclonal- plasma cell malignancy or premalignancy or lymphoma 3. Oligoclonal- small number of bands **CNS test |
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are gamma globulins increased with acute phase reactions
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nope, the gammas are from plasma cells (Ig/AB) and so are increased in more chronic things
1. Polyclonal- chronic infection, autoimmune disease 2. Monoclonal- plasma cell (pre)malignancy or lymphoma 3. Olifocliona- small number of bands **order a CNS test |
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what can an increase in g globulin mean
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increased Ig or AB (from plasma cells)
1. Polyclonal- chronic inflammation, autoimmune disease 2. Monoclonal- B cell (pre)malignancy, lymphoma 3. Oligoclonal- small numnbers of bands **order a CNS test |
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what happens with....
1. decreased g globulins 2. large wide hump of g globulin 3. high skinny peak of g globulin |
1. B cell deficit
2. polyclonal increase- autoimmune, chronic thing 3. monoclonal- b cell malignancy |
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if AST ALT and Alk Phos are normal what disease is it NOT
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liver
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in someone who has high total protein, low albumin and globulins through the roof wat do you do (liver test is normal)
what are the results with regard to the protein called? |
order sesrum protein electrophoresis
no idea |
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where is creatine kinase found? what about the CK isoenzyme CK-MB
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all mm
non specific marker for MI, but will be elevated in MI CK-MB is specific for MI, increased 6 hrs after infarct **these enzymes are reelased from heart cells bc the membrane lysed |
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what are some good cardiac markers
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1. CM-MB
2. Troponin I/T **sensitive for MI/myocardium stays high for a while 3. AST/LD- non specific 4. Myoglobin- non specific |
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what is troponin I/T good for
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cardiac!!!
**specific for myocardium, indicates MI increased 2 hrs post MI and stays high for week |
