Lab Values Flashcards
General Principles
- 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
CBC and Differential
RBC
Hemoglobin
Hematocrit
Platelet count
WBC count & differential (all the different kinds of WBCs)
Hemoglobin
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
What does a low hemoglobin mean
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
Hematocrit
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
Platelet Count
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
WBCs and differential
cells that exist in the blood, lymphatic system and tissues
immune system. protect against infection and have a role in inflammation and allergic reactions
5 types of WBC
Neutrophils - increase with bacterial infection
Lymphocytes - increase with viral infection
Basophils
Eosinophils - increase with allergic reactions
Monocytes
Inflammatory Marker: CRP
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
Electrolytes: most common electrolytes (5)
Sodium
Chloride
Magnesium
Calcium
Potassium
Sodium (Na+)
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.
Chloride (Cl-)(CP7)
- 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
Potassium (k+)
- 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,
Calcium (Ca+)
- 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
Magnesium (Mg)
- 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
Kidney Function Tests
BUN
Creatinine
eGFR
BUN (Blood Urea and Nitrogen)
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
Creatinine
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
eGFR
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.
Liver Function Tests: three primary causes of altered liver function
Altered Synthesis
Primary Liver damage
Altered Biliary Function
Altered Synthesis
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
Primary Liver Damage
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
Altered Biliary Function
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
Lactate Dehydrogenase (LD or LDH)
- 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
