Labs & Markers Flashcards
47, 48, 49
Which lab tests should be performed on a patient to rule out secondary causes of dyslipidemia?
fasting blood glucose (DM), TSH (hypothyroidism), serum creatinine (renal function), UA for proteinuria (kidneys), alkaline phosphatase (liver)
Patients with clinical and angiographic evidence of coronary artery disease tend to have higher plasma levels of …?
homocysteine
It is indicated to check homocysteine levels in which kind of patients?
high-risk patients with family hx of premature atherosclerosis or arterial occlusive disease
High levels of high-sensitivy C reactive protein have been show to show what?
strong independent predictor of cardiovascular and peripheral vascular disease risk and of recurrent cardiac events in patients with history of CAD or Acute coronary syndrome (ACS)
What are the hsCRP values that we should know?
> 3mg/L → marker of high risk for death and MI
1-3 mg/L → intermediate risk
<1.0 mg/L → low risk
What components are included in a basic metabolic panel (BMP)?
Sodium, Potassium, Calcium, Chloride, Carbon Dioxide, Glucose, BUN, Creatinine
A complete metabolic panel has all components of a BMP and what else?
Alkaline Phosphatase, Total Bilirubin, AST/ALT, Total Protein, Albumin
If looking to evaluate liver and kidney function, which metabolic panel would be best?
CMP
If albumin levels are low, what other lab level will also be low?
calcium, half of calcium is bound to Albumin - need to calculate corrected calcium level
What are indications for ordering a metabolic panel?
aid in determining diagnosis, follow course of condition or treatment plan, monitor electrolytes, screen for occult disease
In what heart condition would you see decreased Na levels in a metabolic panel?
CHF
What electrolyte level is critical to monitor if a patient is on diuretic and/or other heart meds?
Potassium
What can high K levels cause?
arrhythmias!
Which particular lab value serves as an index of both kidney and liver function?
BUN
What is better than BUN in indicating renal disease?
creatinine
How do albumin and AST/ALT evaluate the liver?
Albumin tests liver function, where as AST/ALT tell you the integrity of the hepatocytes themselves (inflammation, breakdown). Both will tell you if you have liver disease, and how bad it is.
True/False it is uncommon to have a isolated abnormality on a metabolic panel?
True. You are usually confronted with a group of abnormal values. Exception: glucose
What is considered the old gold standard for myocardial injury?
creatine kinase (CK) has excellent sensitivity but poor specificity
CK levels will rise sharply after the onset of chest pain associated with an acute MI. But, other causes for increased CK include:
any musculoskeletal injury, IM injection, certain medications
What is the isoenzyme of CK that is most specific for myocardial tissues?
CK-MB
What is the biochemical marker of choice in the evaluation of patients with ACS?
cardiac-specific Troponins! (more specific than CK-MB)
Troponins are most beneficial in identifying AMI how many hours or more after symptoms onset?
Typically 6 (3-12 hr range), and will persist for 7-10 days
If a patient’s troponins are normal at presentation, but the clinical index of suspicion is very high, when should the troponin levels be assessed in again?
In 6-12 hours
Which cardiac marker is preferred for early detection of an AMI?
Myoglobin
How soon are elevated myoglobin levels detected and when do they return to normal?
Show 1-4 hours after onset of symptoms and peak 6-7 hours after. Will return to normal 24 hours post-MI
If you suspect a patient has Venous thromboembolism (VTE) which lab test should you order?
d-Dimer (used to diagnose thrombotic disorders)
Is d-Dimer specific for VTE?
No. A negative result can help rule out VTE/PE/DVT/DIC. But it is not specific enough to diagnosis VTE.
What other things can cause a positive d-Dimer test besides VTE?
malignancy, DIC, infection, inflammation, pregnancy
True/False. If myoglobin in normal in the first 6 hours, an MI is very unlikely.
True
What lab value aids in differentiating a patient’s dyspnea from heart failure and non cardiac causes?
B-natriuretic peptide (BNP)
BNP is more specific in which patients, and less so in which?
Circulating levels of BNP increase in proportion to the severity of HF, and BNP is detectable even with minimal clinical symptoms.
A patient has a heart attack and 3 days later is having chest pain with an elevated Myoglobin level. What is the most likely cause?
Re-infarction. Myoglobin goes back to normal within 24 hours of MI, so a new rise indicates a new attack.
What other things can cause an elevated troponin?
CHF, pulmonary embolism, renal failure, rhabdomyolysis, kidney injury, any other things that can have repercussions on the heart.
Typical criteria for diagnosis of AMI requires total CK elevation of how much?
twofold above normal
Which lab test has a rough correlation with the size of the infarction?
CK-MB
A relative index can be used to differentiate a cardiac cause vs a muscle cause of an elevated CK-MB. What is it?
CK-MB/total CK x 100. If is greater than 2 indicated myocardial necrosis
61 year old woman with a history of tobacco abuse and fam hx of CAD presents to ED after 1 hr of chest “discomfort”. EKG shows normal sinus rhymth. Which lab test do you order?
Myogblobin - is the earliest marker for AMI
Which lab value is both high specific and sensitive to ruling in or out MI?
Troponin I - if normal, essentially can R/O MI, if elevated, confirms MI
Patient has elevated D-dimer and Troponin T, what is most likely cause?
PE
How routinely do you draw for cardiac markers?
Depends on your institution - but frequently at 0, 4, 8, 12, hours OR 6-8 hours for 24 hours
If initial testing indicates a hs-CRP level that is very high (>10), the test should be repeated when?
in about 2-3 weeks
Is Lipoprotein-A (an LDL-like particle) included in a routine lipid panel?
No. But it is thought to contribute to atherosclerosis, but NCEP does not recommend widespread screening.
In who would a Lp-A level check be indicated in?
Pts with lipid disorders, intermediate cardiovascular risk, or a strong family history of premature CVD
Conditions that are associated with an elevated BNP:
HF, LVH, myocarditis, pulmonary hypertension
For patients with CHF, BNP levels will generally be above____?
100 pg per mL (usually normal values are <50)
