Ammonia, C-Reactive, D-Dimer, ESR, ethanol, HbA1C Flashcards
What is the Ammonia test used for?
Normal Range?
Test used to support the diagnosis of severe liver disease (fulminant hepatitis or cirrhosis) and for monitoring of these diseases.
Also used to diagnose and follow up hepatic encephalopathy (altered level of consciousness due to liver failure)
Normal: 10-80 mcg/dL
How is Ammonia made and catabolized?
Ammonia is a byproduct of protein catabolism, most of which is made by bacteria acting on proteins in the gut.
It goes to the liver via the portal vein and is then converted into urea and excreted by the kidneys.
Ammonia cannot be catabolized with severe liver disease.
What are the Interfering Factors for Ammonia?
Hemolysis increases levels as RBCs have 3 times the ammonia level as the plasma.
Muscular exertion increases levels.
Cigarette smoking can increase levels within 1 hour of inhalation.
May be factitiously elevated if tourniquet is too tight for too long.
Drugs that increase ammonia levels include acetazolamide, alcohol, ammonium chloride, barbiturates, diuretics, narcotics, and parenteral nutrition.
Drugs that decrease levels include neomycin, lactobacillus, lactulose, potassium salts.
What can cause Increased levels of Ammonia?
Primary hepatocellular disease, Reye syndrome, asparagine intoxication – not enough functioning liver cells to metabolize the ammonia
Portal hypertension, severe heart failure with congestive hepatomegaly – portal blood flow from gut to liver is altered and ammonia cannot get to liver to be metabolized. Ammonia from gut is shunted around the liver via gastroesophageal varices and into system circulation
Hemolytic disease of newborn (erythroblastosis fetalis) – RBCs contain high amount of ammonia and newborn liver not mature enough to metabolize all the ammonia
GI bleeding with mild liver disease, GI obstruction with mild liver disease – ammonia production is increased because bacteria have more protein (blood) to catabolize. Impaired liver can’t keep up with the increased load
Hepatic encephalopathy and hepatic coma – ammonia acts as false neurotransmitters so the brain cannot function properly
Genetic metabolic disorder of urea cycle – ammonia normally catabolized by urea cycle
Hyperornithinemia
What causes Decreased levels of Ammonia?
Essential or malignant hypertension
What is the C-Reactive Protein (CRP) used for and what are the normal values?
CRP is a nonspecific acute phase reactant protein used to indicate an inflammatory illness
CRP is used to diagnose bacterial infectious disease and inflammatory disorders such as rheumatic fever and rheumatoid arthritis.
Normal < 1.0 mg/dL
What does a positive C-Reactive Protein test indicate?
It indicates the presence, but not the cause, of the disease.
Is the C-Reactive Protein test more or less responsive than the erythrocyte sedimentation rate (ESR)?
It is a more sensitive and rapidly responding indicator than erythrocyte sedimentation rate (ESR). CRP shows up earlier with a more intense increase than ESR, and with recovery, the CRP returns to normal before the ESR.
What are the interfering factors for the C-Reactive Protein test?
CRP will increase with hypertension, elevated body mass index, metabolic syndrome, diabetes, chronic infection, chronic inflammation, and low HDL/high triglycerides
Cigarette smoking can increase levels
Decreased levels can occur with moderate alcohol consumption, weight loss, and increased activity or endurance exercise
Drugs that increase CRP are estrogens and progesterones
Drugs that decrease CRP are fibrates, niacin, and statins
What can cause increased levels of the C-Reactive Protein?
Acute noninfectious inflammatory reaction (arthritis, acute rheumatic fever, Reiter syndrome, Crohn disease), collagen vascular diseases (vasculitis, lupus erythematosus), tissue infarction or damage (MI, pulmonary infarction, kidney or bone marrow transplant rejection, soft tissue trauma), bacterial infections such as postoperative wound infection, UTI, or TB, malignant disease, bacterial infection (TB, meningitis) – all cause an inflammatory reaction that leads to synthesis of CRP
Increased risk for cardiovascular ischemic events – inflammation of the intimal lining of a blood vessel, especially coronary vessels, is associated with increased risk for intimal injury leading to distal vessel plaque occlusions
What is the D-Dimer used for and what are its normal levels?
Used to identify intravascular clotting
D-dimer is a fibrin degradation fragment that is made through lysis of cross linked fibrin. As plasmin acts on the fibrin polymer clot, fibrin degradation products and D-dimer are produced.
D-dimer assay provides a highly specific measurement of the amount of fibrin degradation that occurs
Normal plasma doesn’t have detectable amounts of fragment D-dimer
Normal < 0.4 mcg/mL
D-Dimer has been used as a screening test for what diseases?
It has been used as a screening test for DVT and PE
Is the D-Dimer useful in high or low risk patients?
Low Risk
What can cause increased levels of D-Dimer?
DIC – rapid intramicrovascular coagulation and synchronous fibrinolysis. D-dimer produced by action of plasmin on fibrin polymer clot
Primary fibrinolysis, during thrombolytic or defibrination therapy – D-dimer produced by action of plasmin on fibrin polymer clot
Deep vein thrombosis, pulmonary embolism, arterial thromboembolism, sickle cell anemia with or without vasoocclusive crisis – natural reaction to clot development is fibrinolysis
Pregnancy, malignancy, surgery – have varying degrees of clotting and fibrinolysis
Age, inflammatory conditions, cancer – cause D-dimer to be elevated
What is the Erythrocyte Sedimentation Rate (ESR) used for? And what are the normal levels?
ESR is a nonspecific test used to detect illnesses associated with acute and chronic infection, inflammation (collagen-vascular diseases), advanced neoplasm, and tissue necrosis or infarction
ESR is a measurement of the rate at which the RBCs settle in saline solution or plasma over a specified time period.
Test is nonspecific and therefore not diagnostic for any particular organ disease or injury
Normal: up to 15-20 mm/hr.
What diseases can Erythrocyte Sedimentation Rate be used to monitor the disease therapy?
ESR is a fairly reliable indicator of the course of disease so can be used to monitor disease therapy, especially for inflammatory autoimmune diseases (temporal arteritis, polymyalgia rheumatica). As the disease worsens, the ESR increases; as the disease improves, the ESR decreases
When is the CRP used instead of the ESR?
If ESR is inconclusive or inconsistent with clinical impressions, the CRP is used.
What are the interfering factors for the Erythrocyte Sedimentation Rate?
Falsely low results occur when specimen is allowed to stand > 3 hours before running the test
Pregnancy (2nd and 3rd trimester) can cause elevated levels
Menstruation can cause elevated levels
Tube must be perfectly vertical – tilt alters results
Some anemias can falsely increase ESR.
Polycythemia is associated with decreased ESR
Diseases with increased proteins can falsely increase ESR
Drugs that cause increased ESR include methyldopa, oral contraceptives, procainamide, theophylline, and vitamin A
Drugs that cause decreased ESR include aspirin, cortisone, and quinine
What can cause increased levels of the Erythrocyte Sedimentation Rate?
Chronic renal failure (nephritis, nephrosis)
Malignant diseases (multiple myeloma, Hodgkin disease, advanced carcinomas) – have increased abnormal serum proteins to increase the ESR
Bacterial infection (abdominal infections, acute pelvic inflammatory disease, syphilis, pneumonia), inflammatory diseases (temporal arteritis, polymyalgia rheumatica, rheumatoid arthritis, rheumatic fever, SLE), necrotic diseases (acute MI, necrotic tumor, gangrene of an extremity) – ESR is an acute phase reactant protein and is elevated
Diseases with increased proteins (hyperfibrinogenemia, macroglobulinemia) – diseases with increased proteins have increased ESR
Severe anemias (iron deficiency or B12 deficiency) – lower RBC volumes leads to the RBCs settling faster
What can falsely decrease the Erythrocyte Sedimentation Rate?
Sickle cell anemia, spherocytosis – diseases that distort the RBC have decreased ESR
Hypofibrinogenemia – diseases with decreased proteins inhibit sedimentation of RBCs
Polycythemia vera – increased cells in the blood inhibit sedimentation of RBCs
What is Ethanol used for? Critical values?
Used to diagnose alcohol intoxication and overdose
Critical values > 300 mg/dL
Proper collection, handling, and storage of blood sample is important for medical/legal cases involving sobriety
What can levels of Ethanol greater than 80 mg/dL cause?
greater than 100 mg/dl?
Levels greater than 80 mg/dL may cause flushing, slowing of reflexes, and impaired visual acuity.
Depression of the CNS occurs with levels over 100 mg/dL, and fatalities are reported at levels over 400 mg/dL
Levels over 100 mg/dL may cause hypotension
What are the Interfering Factors for Ethanol?
Elevated blood ketones (DKA) can cause false elevation
Alcohols other than ethanol, such as isopropyl (rubbing) or methanol (grain), will also be detected
Use of large amounts of isopropyl in cleansing skin can falsely elevate the test results – can use povidone iodine or peroxide instead
What can cause Increased levels of Ethanol?
Alcohol intoxication or overdose – alcohol rapidly absorbed from stomach in about 1 hour, faster if the stomach is empty.
Alcohol is metabolized in the liver. An average 70 kg person with normal liver function can metabolize about 15 mg alcohol per hour.
What is the clinical sobriety tool?
If have patient in ER, you can discharge them before their alcohol levels reach normal, as long as they pass this test and can walk.
You might have them count backwards from 100 for example.
What is Glycosylated Hemoglobin (Hemoglobin A1C ) used for? Normal values?
Used to monitor diabetes treatment by providing an accurate long term index of the patient’s average blood glucose level.
Normal findings: Nondiabetic: 4-5.9% Good diabetic control: < 7% Fair diabetic control: 8-9% Poor diabetic control: > 9
What is Hemoglobin A1C? (How does it work?)
About 98% of hemoglobin in RBCs is hemoglobin A, and about 7% of hemoglobin A consists of hemoglobin A1 that can strongly bind to glucose by glycosylation, which is not easily reversible. HbA1C is a component of hemoglobin A1 that most strongly combines with glucose.
HbA1C makes up the majority of HbA1 , and about 70% of HbA1C is glycosylated.
As RBCs circulate, they combine their HbA1 with some of the glucose in the bloodstream to form HgA1C , the amount of which depends on the amount of glucose available in the blood stream over the RBC’s 120 day life span.
HbA1C value reflects the average blood sugar for the 100-120 days (the lifespan of the RBC) prior to the test. The more glucose the RBC is exposed to, the higher the percentage
What are the Test Benefits for Glycosylated Hemoglobin (Hemoglobin A1C ) ?
Evaluates the success of diabetic treatment and patient compliance.
Compares and contrasts the success of past and new forms of therapy.
Determines duration of hyperglycemia in newly diagnosed diabetics.
Provides sensitive estimate of glucose imbalance in mild diabetics.
Individualizes diabetic control regimens.
Provides sense of reward for patients when test shows good control.
Evaluates diabetics whose glucose levels change significantly day to day (brittle diabetics).
Differentiates short term hyperglycemia in nondiabetics (recent stress or MI) and diabetics (glucose is persistently elevated)
How does the HbA1c relate to the mean plasma glucose (MPG) level?
HbA1C can be correlated with the daily mean plasma glucose (MPG) level, which is helpful for diabetics and health care professionals in determining and evaluating daily glucose goals.
Each 1% change in HbA1C represents a change of 35 mg/dL in the MPG
What are the interfering factors for Glycosylated Hemoglobin (Hemoglobin A1C ) ?
Hemoglobinopathies can affect results because the quantity of hemoglobin A varies with these diseases.
Falsely elevated levels occur when RBC life span is lengthened – longer period available for glycosylation
What causes Increased levels of Glycosylated Hemoglobin (Hemoglobin A1C ) ?
Newly diagnosed diabetic patient.
Poorly controlled diabetic, nondiabetic hyperglycemia (acute stress response, Cushing syndrome, pheochromocytoma, glucagonoma, corticosteroid therapy, acromegaly) – these illnesses all have persistently elevated glucose levels.
Patients with splenectomy – RBC survival is prolonged.
Pregnancy – gestational diabetes or prediabetes
What causes Decreased levels of Glycosylated Hemoglobin (Hemoglobin A1C ) ?
Hemolytic anemia, chronic blood loss – shortened RBC survival.
Chronic renal failure – reduced hemoglobin levels due to lack of erythropoietin which is produced in the kidney
