Lab Values

Question 1

General Principles

Answer 1

• lab and/or diagnostic tests are supportive tools in arriving at a differential diagnosis
• lab values should confirm or explain what we already know. there should rarely be surprises
• lab tests can be helpful in diagnosis, but they are also helpful in trending out patients responses to therapeutic interventions
• medications can impact our patients’ bodies and can alter their bloodwork results. We must be mindful of this when giving medications and monitor lab results accordingly
  They are rarely diagnostic

Question 2

CBC and Differential

Answer 2

RBC
Hemoglobin
Hematocrit
Platelet count
WBC count & differential (all the different kinds of WBCs)

Question 3

Hemoglobin

Answer 3

the protein component of the RBC that saturates with oxygen and carries it to the tissues
oxygen carrying capacity of the RBC.
High value is rarely linked to pathological condition (blood doping, higher elevations)
RBCs only live for 3 months
135-185 is normal value

Question 4

What does a low hemoglobin mean

Answer 4

blood loss, inadequate nutrition, renal failure where lack of erythropoietin stimulating the bone marrow to produce RBCs
present as weak, fatigued, dizzy, pale, SOB, cold, tachycardic, tachypnic, chest pain, lethargic.
Transfusions are given if Hgb is 70
Rapid fluid resuscitation can cause hemodilution and decrease concentration of hemoglobin thus decreasing oxygen carrying capacity

Question 5

Hematocrit

Answer 5

the proportion of RBCs relative to other blood components that make up a sample
Males: 41-50%
Females: 36-44%
high levels: dehydration, hypoxia, cigarette smoking, polycythemia vera, erythropoietin abuse
low levels: overhydration, nutritional deficiencies, blood loss, bone marrow suppression, leukemia, lead poisoning.
Levels of RCSs, Hgb, Hct usually fluctuate similarly

Question 6

Platelet Count

Answer 6

measures number of platelets - colourless blood cells integral to clotting.
150,000-400,000/microliter of blood
- patients are usually asymptomatic with low levels unless they have a level less than 50,000
Low number: thrombocytopenia caused by ineffective bone marrow production of platelets or accelerated destruction of platelets.
Treated with IV platelets or IV Ig which prevents the spleen from destroying platelets
high number: thrombocytosis

Question 7

WBCs and differential

Answer 7

cells that exist in the blood, lymphatic system and tissues
immune system. protect against infection and have a role in inflammation and allergic reactions

Question 8

5 types of WBC

Answer 8

Neutrophils - increase with bacterial infection
Lymphocytes - increase with viral infection
Basophils
Eosinophils - increase with allergic reactions
Monocytes

Question 9

Inflammatory Marker: CRP

Answer 9

C-Reactive Protein
Trending diagnostic test
A protein made by the liver
increased levels indicate non-specific inflammation
released within a few hours after injury, start of infection, or inflammation

Question 10

Electrolytes: most common electrolytes (5)

Answer 10

Sodium
Chloride
Magnesium
Calcium
Potassium

Question 11

Sodium (Na+)

Answer 11

Present in all body fluids and vital to nerve and muscle function
- LOW sodium: natriuretic peptide, decreased aldosterone. Too much fluid or too little sodium. Nausea, vomiting, headache, confusion, loss of energy, drowsiness, fatigue, muscle weakness, cramps, irritability
- HIGH sodium – too much sodium or too little water. Thirst, CNS impairment, confusion, neuromuscular excitability, hyperreflexia, seizure or coma
o Draws water out of cells into the bloodstream which is particularly dangerous for braincells
- Sodium is found in the highest concentrations in the blood and extracellular fluid
- Regulated by the kidneys – body uses what it needs and the rest is eliminated in the urine
- 135-145
- The body regulates this level by producing hormones that can either increase or decrease the amount of sodium in the urine (natriuretic peptides or aldosterone) antidiuretic hormone (prevents water losses) and controlling thirst.

Question 12

Chloride (Cl-)(CP7)

Answer 12

• LOW number indicate: Emphysema, chronic lung disease, vomiting
• High number indicates dehydration, kidney disease, or hyperventilation
• Found in all body fluids: highest concentration in the blood and ECF
• Most of the time chloride concentrations mirror those of sodium
• Increasing and decreasing for the same reasons and in direct relationship to sodium
• When there is an acid base imbalance, blood chloride levels can change independently of sodium levels as chloride acts as a buffer and helps maintain electrical neutrality

Question 13

Potassium (k+)

Answer 13

• A critical lab value to assess
  o Found in all body fluids but most is found within the cells. Primary intracellular ion
  o Body keeps it within a very small range (3.5-5)
  o Levels are regulated by aldosterone – hormone produced by adrenal glands
  o Minor changes can have significant health effects.
   Shock, breathing problems, irregular heartbeats, or the heart muscle can lose its ability to contract
• Low number indicates: (low dietary intake, blood loss, nausea, vomiting, diarrhea, renal loss due to diuretics – can all impact potassium levels)
• High number indicates: renal failure,

Question 14

Calcium (Ca+)

Answer 14

• Total and Ionized
• Most abundant and one of the most important minerals in the body
• Essential for cell signaling and proper function of muscles, nerves and the heart. Needed for blood clotting and crucial for formation, density, and maintenance of bones and teeth.
• Blood test includes ionized calcium in the body
• 99% is in the bones and 1% is in the blood
• Calcium levels are tightly controlled, if there is too little calcium ingested or too much released in the urine calcium is taken from the bone to maintain concentration. 50% is ionized and free to be used. 50% is bound to proteins, primarily albumin. Bound forms are metabolically inactive.
• Total measures free and bound form
• Ionized test measures only free metabolically active form
• Can test in the urine
• What does a LOW level mean? Hypocalcemia
  o Tuberculosis, fungal and mycobacterial infections, HIV/AIDS, hyperparathyroidism (too much PTH released), metastatic bone tumor, multiple myeloma, hyperthyroidism (too much Calcitonin release)
• What does a HIGH level mean?: Hypercalcemia
  o Malnutrition, vitamin D deficiency, hypoparathyroidism, low blood level of albumin, kidney failure, magnesium deficiency, liver disease, pancreatitis

Question 15

Magnesium (Mg)

Answer 15

• A mineral that is vital for energy production, muscle contraction
• Stored in bones cells and tissues, and only 1% is found in the blood which makes it difficult to measure
• Body regulates its level by regulaing how much it absorbs in the gut and how much it excretes in the kidneys
• Low level: hypomagnesemia
  o Chronic diarrhea, alcoholism, hemodialysis, ulcerative colitis, delirium, hypoparathyroidism, hyperaldosteronism, hepatic cirrhosis, pancreatitis, toxemia of pregnancy
  o None or few nonspecific symptoms. Nausea, loss of appetite, fatigue, confusion, muscle cramps
• High level:
  o Oliguria, dehydration, Addison disease, chronic renal failure, diabetic acidosis
  o Ingested antiacids with magnesium in them
• Gut and the kidneys involved
• This is why doctors order extended electrolytes. Symptoms are similar across electrolyte abnormalities

Question 16

Kidney Function Tests

Answer 16

BUN
Creatinine
eGFR

Question 17

BUN (Blood Urea and Nitrogen)

Answer 17

A waste product formed in the liver from protein breakdown. It is carried to kidneys then filtered out of blood and excreted in the urine
- If the kidneys are not functioning properly then the levels are going to be higher because the BUN is not being excreted, it is remaining in the bloodstream
- Don’t typically see low levels

Question 18

Creatinine

Answer 18

a chemical waste produced by muscle metabolism (breakdown of a compound called creatine)
- Removed from body by the kidneys – filter almost all of it
- Creatine is part of the cycle that is necessary to produce energy to contract muscles. Creatine and creatinine are produced at a relatively constant rate.
- Blood levels are a great indicator of how well the kidneys are functioning. If levels are high the kidneys are not functioning well
- Levels are naturally higher in men then in women because they have more muscle mass

Question 19

eGFR

Answer 19

60ml/hr or more. When it drops we look at number in correlation with BUN and Creatinine and look at the clinical picture. Look at old lab values. Is it CKD or AKI
When there is alteration in kidney function you look at the electrolytes because they are the ones that regulate levels.

Question 20

Liver Function Tests: three primary causes of altered liver function

Answer 20

Altered Synthesis
Primary Liver damage
Altered Biliary Function

Question 21

Altered Synthesis

Answer 21

Albumin - The liver produces albumin – always declines in liver disease although it can also decline in non-hepatic causes such as malabsorption, reduced protein intake, spilling into urine
PT - The liver produces clotting factors (measured by PT)
o How much time it takes for the time to clot. Increased in liver disease. Non hepatic causes could be a vit K deficiency, intake of anticoagulants or a bleeding disorder
- These tests will be altered in altered synthesis but the values may also be affected by other conditions so they are non-specific to the liver though liver disease will impact them

Question 22

Primary Liver Damage

Answer 22

AST
ALT - more specific to the liver
- Both are elevated in liver disease but can also be elevated for different reasons such as MI, muscle disease. The AST is elevated more than the ALT in non-hepatic scenarios

Question 23

Altered Biliary Function

Answer 23

Total Bilirubin - – elevated levels of this means elevated levels of conjugated and unconjugated bilirubin and will have our patient appearing jaundiced.
Alkaline Phosphatase (ALP) - Found in the small bile ducts of the canaliculi of the liver
GGT - Found in the small bile ducts of the canaliculi of the liver
o Damage to these canaliculi causes elevation in these values. Greater increase in GGT than ALT when biliary disease is the cause
o GGT is not present in bone. Because they are present in other areas ALT (bone and placenta), GGT (kidneys, pancreas and intestine), they can be elevated when damage occurs to these other structures as well
o NON-HEPATIC causes of increased ALP: bone diseases, lymphoma, chronic renal infection

Question 24

Lactate Dehydrogenase (LD or LDH)

Answer 24

• What is being tested?
  o Lactate dehydrogenase (LD or LDH) is an enzyme involved in energy production that is found in almost all of the body’s cells, with the highest levels found in the cells of the heart, liver, muscles, kidneys, lungs, and in blood cells; bacteria also produce LD. This test measures the level of LD in the blood or sometimes other body fluids
• Often ordered as part of LFTs, but not always
• Older tests – not often ordered
• More of a blood test for trending tissue damage than it is diagnostic for any one condition

Question 25

Prothrombin Time (PT)

Answer 25

- PT stands for prothrombin time. It is a measure of how quickly blood clots. The traditional method of performing a PT test is to have your blood drawn and sent to a lab. At the lab, a substance called a reagent is added to your blood. The reagent causes the blood to begin clotting. The PT result is the time in second that is required for the blood to clot - Blood plasma normally takes between 11 and 13.5 second to clot if you’re not taking blood-thinning medication. PT results often are reported as an international normalized ratio (INR) that’s expressed as a number

Question 26

International Normalized Ratio (INR)

Answer 26

NORMAL is 0.9-1.2 – ratio, not an absolute value which is why it has no units attacked to it - This number goes along with out PT because different reagents are used around the world for causing blood to clot. In the lab when you are talking INR, INR standardizes reagents and allows us to comare when talking blood clotting - What does a HIGH number mean? o The higher the INR is, the longer it takes your blood to clot therefore the risk of bleeding increases - What does a LOW number mean? o The lower the INR the slower the blood clots putting you at risk for clotting - The PT/INR is trended when a patient is on warfarin - The reversal agent for this medication if the INR/PT is to high is vitamin K

Question 27

Activated Partial Thromboplastin Time (aPTT)

Answer 27

- Screening test that helps evaluate a person’s ability to appropriately form clots - Assess the amount and function of certain proteins in the blood called clotting factors that are part of blood clot formation - How is it different than PT/INR: PT and APTT test different groups of factors that are part of different reactions in the clotting cascade called intrinsic, extrinsic and common pathways. PT is part of a different pathway than PTT - Measures the number of seconds it takes for a clot to form - PTT is used when a patient is on Heparin - The reversal agent for this medication is protamine sulfate or they will stop the infusion IMPORTANT NOTE!!!

Question 28

Cardiac Markers

Answer 28

High Sensitivity Troponin Brain Natriuretic Peptide (BNP)

Question 29

High Sensitivity Troponin

Answer 29

- HS – Troponin o Can get false positives with high sensitivity - Troponin T – group of proteins that regulate muscle contraction and are found in the heart. Trop test measures the amount of cardiac specific troponin in the blood to help detect heart injury - There are three types of troponin protein: C T and I. Cardiac specific are T and I and measuring them can help identify those who have experienced damage to their heart - Want it to be sensitive so when it is high it is indicating heart distress - Can help ID patients who have experienced damage to their heart - Normally almost undetectable in the blood – when there is damage to the heart muscle troponin is released in the blood when the cells die and release their contents. The greater the damage the greater the value. Help determine if a patient had a heart attack and for evaluating other forms of heart injury - Can be elevated in patients with stable angina even when they are without symptoms; indicates increased risk of future heart events - Levels can become elevated within 3-4 hours after injury. This is faster than it used to be and so acute coronary syndrome can be detected sooner - Can remain elevated for 10-14 days following injury o Want to be looking at the trending downward if they had surgery or an injury to their heard in the last two weeks instead of seeing a high value and thinking they are having another heart attack

Question 30

Brain Natriuretic Peptide (BNP)

Answer 30

- A small protein that is continually produce in the heart - Released in larger quantities when the heart is having to work harder - Supports fluid retention and volume expansion iintravascularly - Tested when Heart Failure is suspected o More amounts when the heart has to pump harder o Fluid retention, chronic heart problems o Marker to trend and track the degree of heart failure and response to treatment - Produced in the left ventricle – associated with blood volume and pressure and the work the ventricle must do to pump blood to the rest of the body. When it is having difficulty pumping sufficient blood to the body the concentration of BNP produced can increase markedly. - Got its name because it was first found in the brain - One marker that helps track and trend when left-sided heart failure is suspected

Question 31

Normal Urinalysis: Appearance and Color

Answer 31

- Clear to dark yellow – normal - Amber to honey yellow – dehydration - Orange – dehydration, intake of rifampicin, consumption of food dye - Brown ale – severe dehydration, liver disease - Pink to reddish – consumption of beets, rhubarb or blueberries, mercury poisoning, tumors, kidney diseases, prostate problems, UTI. RBCs can be found with kidney stones - Blue or green – consumption of asparagus, genetic disorders, excess calcium, heartburn medications, multivitamins - Deep purple – porphyria

Question 32

Normal Urinalysis: Odor

Answer 32

- Fairly odorless is normal - Concentrated urine will smell of ammonia - UTI will give it a foul odor

Question 33

Normal Urinalysis: Protein

Answer 33

- Shouldn’t normally be seen - Albumin is the first protein to be seen in the urine - Causes: preeclampsia, multiple myeloma, inflammation, urinary tract injuries, malignancies and other disorders that destroy RBCs, nephrotic syndrome (proteinuria, hypoalbunemia, and edema) - Protein is not a normal finding - If you find it, especially a large amount you should be wondering what is going on

Question 34

Normal Urinalysis: Ketones

Answer 34

- Can be normal in certain states but typically don’t spill into the urine - They are by-products of fat metabolism and form when there is not enough carbohydrate energy production - Also form when insulin levels are not enough to initiate carbohydrate metabolism so the body uses fat - Diabetic ketoacidosis – high levels in the urine - Other conditions – diabetes, DKA, frequent vomiting, strenuous exercise and high-protein diet can cause ketones

Question 35

Normal Urinalysis: Nitrites

Answer 35

- When bacterial infection is present in a urinary tract the bacterial flora convert the urines nitrate compound to nitrite. - Detection of nitrites is not diagnostic of a UTI solely - If we get WBC and nitrites in addition to symptoms those are classic indicators