223 Laboratory and Diagnostic Medicine Flashcards
Purpose of labs
Diagnosis, monitoring, screening, research
What is included in a CBC
Rbc, wbc, platelets, Hct, Hgb
Relevance of Hct and normal range
% of formed elements in VBG, not specific. Low cells or high plasma.
(F) 0.36-0.47
(M) 0.4-0.52
Relevance and normal value of Hgb
Protein responsible for carrying O2 (and CO2)
(F) 120-160g/L
(M) 140-180g/L
Relevance and normal values of WBC
Total does not differentiate.
Low (leukopenia)- certain anemias, vitamin deficiencies, sepsis
High (leukocytosis)- inflammation, infection, stress of trauma, malignancy, CVS conditions, steroids
Leukopenia <
4,000-11,000 /microL
>Leukocytosis
What is on the white count differential
“Never let monkeys eat bananas”
Neutrophils, lymphocytes, monocytes, eosinophils, basophils
Neutrophils: function and relevance
“First wave” attack via phagocytosis
Elevation should prompt investigation for BACTERIAL infection
Normal 40-60% of total WBCs
What is a left shift and why is relevant?
A “left shift” is when there is an abundance of band cells (immature neutrophils). Think left shift on the timeline of maturity. In bacterial infection (but not other stress), % band cells will be elevated
Lymphocytes: rôle and function
B cells must be primed by antigen to produce antibodies (immunoglobulins)
T cells secrete cytokines to attract other immune cells and or become cytotoxic and kill infected/abnormal cells
NK just attack without prejudice (no priming)
Elevated % should prompt for investigation of VIRAL infection
Normal is 22-44% of total WBC. Differential provides total, not breakdown of B, T, NK
Role and function of monocytes
“2nd wave attack” ID and phagocytize bacteria, similar to neutrophils but made faster and last longer. Monocytes become macrophages when they pass into tissue and get larger.
Normal is 3-9% of total WBCs
Role and function of eosinophils
ID, seek, destroy via
Increase inflammation by causing production of proinflammatories (prostaglandins, cytokines, leukotrienes)
Increase most often indicates parasitic infection, atopic allergic reaction (asthma, dermatitis, etc) or certain cancers
Steroids, certain conditions (cushings), and bacteremia drop eosinophil count
Normal 1-6% of total WBCs
Role and function of basophils
Antibodies on surface, primed for IgE, Contain heparin and histamine
Particularly elevated during allergic reaction and infections of insects such as ticks
Normal is 0-2% of total WBCs
What is on Chem-7 and normal values
Aka metabolic panel
1. Na+ 135-145mmol/L
2. K+ 3.5-5.0mmol/L
3. Cl- 98-106mmol/L
4. HCO3- 22-28mmol/L
5. Urea (BUN) 3-7mmol/L
6. Creatinine (f) 55-100
(m) 80-115micromol/L
7. GFR 90-120mL/min/1.73^2
8. Glucose 3-6mmol/L
What is urea
Measured as BUN
Product of protein catabolism
May be caused by decreased renal function, consumption of high-protein diet, or high-protein catabolism state (exp. Burns or crush), therefore not reliable indicator of kidney function
Elevated BUN, but normal creatine may indicate upper GI bleed or pre-renal AKI
What is creatinine
Waste product from muscle metabolism (creatine, storehouse for energy). Not reabsorbed in tubules.
More reliable indicator of kidney function
BUN:creatine ratio
Urea- significant % reabsorbed at tubules.
Creatine is not reabsorbed.
Low perfusion= slower filtration rate and thus more urea being reabsorbed causing disproportionate increase in BUN to creatinine.
Normal is 10:1 to 20:1
What is GFR
Measure of overall filtration efficiency, not possible to directly measure. Used to trend chronic disorders and to calculate appropriate fluids/electrolyte tx.
eGFR= creatinine clearance
Compares amount of creatinine excreted in urine with amount in blood over 24hrs
What is on extended lytes panel
Mg2+ important for ATP production and other functions. 70% in bones, 30% in serum. Cleared in loop of henle (watch when loop diuretics use).
PO4- Important for ATP production
iCa2+ = unbound/active dispersed in body fluid. Other bound to proteins (ie. albumin) and other molecules (citrate, lactate, phosphate, sulfate)
What is on LFT panel
Enzymes- indicate injury NOT function
- Asparate aminotransferase (AST)
- Alanine aminotransferase (ALT) slightly more specific than AST because found in fewer organs
- alkaline phosphates (ALP) used to dx common bile duct obstruction
- gamma-glutamyl transferase (GGT) in conjunction with ALP, used to dx hepatic and biliary disease
- Amylase used to assess pancreatic insufficiency/damage, bile duct obstructions and head trauma
-Lipase more specific than amylase in dx of pancreatic disease, prone to elevation in bile duct obstruction or disease
FUNCTION- produced by liver
- Albumin 40g/L, large plasma protein causing oncotic effect. Binds and deactivates lots of Rx
- Bilirubin (total) by-product of Hgb breakdown, biliary tract obstruction, RBC hemolysis.
- conjugated/ direct bilirubin able to be excreted
Other:
Protein C, protein S, PT, aPTT, INR, glucose
What is on coagulation panel
INR, aPTT, fibrinogen, d-dimer, platelets
What is INR
International normalized ratio. Normalizing index of PT (rate of conversion of prothrombin to thrombin, representing function of EXTRINSIC pathway)
Normal is 1.1-3.0, therapeutic target is 2.0-3.0
May be elevated in liver disease, warfarin tx
May be decreased in low levels of VitK, DIC or after massive transfusion
What is aPTT
Activated partial thromboplastin time
Indicates health of INTRINSIC and COMMON pathways. Measured when heparin is used.
Normal is 25-40sec, therapeutic target is 60-90sec
Elevated: hemophilia A or B, von Willebrand disease, DIC
What is fibrinogen/factor I
Part of common pathway, thrombin cleaves fibrinogen into fibrin
What is d-dimer
Fragment of clog breakdown, may indicate clotting issue, but not specific.
High: DVT, PE, DIC, CVA, COVID-19
False +: old, smoking, obese, pregnancy, sx, trauma, infection, heart, disease, RA
What is on cardiac panel and why order it
hs/Troponin (I, T, C), CK-MB, CK, BNP and ANP
ACS, HF, valve problems, post-sx, arrhythmia, -carditis, dissection.
Troponin leak may also be from renal problem (not clearing troponin) or SAH (excessive release of norepi from cardiac sympathetic nerves causes LV systolic dysfunction, cardiogenic shock, pulmonary edema)
What is in urinalysis panel
Colour, clarity, odour
Specific gravity (high is dark and concentrated)
pH
Protein (nephron problems)
Glucose
Nitrites (indicates UTI, bacterial enzyme converts nitrate to nitrite)
Leukocytes
Ketones
Name 6 things to check before reviewing lab/dx studies
Pt name and ID #, type of sample taken, location of sample, date of test, time of test, supporting data
Define precision
Every time a particular lab test is performed, the value will be the same.
High precision= tightly packed values. Does not reflect how well the measurements compare with the true value
Define accuracy
Measure of the likelihood that an average of a set of test values will be the same as the individual values in the set. Or if the value measured conforms with the true value
Define specificity
The ability of a certain test to indicate whether a person does NOT have a certain disease
Define sensitivity
The ability of a certain test to indicate whether a person has a certain disease
Define “normal range”
Range of values encompassing the results that 95% of healthy people would have for the particular test
Define quantitative
A quantitative test indicates the exact amount
Define qualitative
A qualitative test confirms presence/positive or absence/negative, does not identify specific level
Indications for urinalysis
Reduction in GFR, unexplained albuminuria, or suspected kidney disease
What are the three components of urinalysis
Gross/macroscopic, dipstick, microscopic
What is macroscopic urine evaluation
Light or dark, colour, clarity/turbidity, odour
What is microscopic urinanalysis
Evaluates urine sediment which includes cellular elements (RBCs, WBCs- neutrophils and eosinophils, epithelial cells from urinary tract), casts, crystals, microorganisms, and urinary lipids.
Sample is centrifuged and supernatant poured out, leaving pellet to be resuspended and gently agitated.
Name the colours urine can be and common causes
Red/brown- hematuria, hemoglobinuria, myoglobinuria, Rx (rifampin, phenytoin, hydroxycobalamin), food (beets, rhubarb, senna), dyes, acute intermittent porphyria
White- phosphate, crystals, chyluria, PROPOFOL
Pink- methylene blue, propofol, amitryptiline, UTI
Black- hemoglobinuria, myoglobinuria, Melanuria
Purple- bacteria from urinary catheter, methylene blue + hydroxycobalamin
What causes turbidity in urine
Infection, crystals, chyluria (rare condition, lymph leaks into kidneys), or contamination from genital secretions
What causes urine odour
Ammonia from bacteria, ketones, other rare diseases
What is on a urine toxicology screening test
Alcohol, amphetamine
Barbiturates, BZs
cocaine
Heroin
Ketamine
Marijuana, methadone
Opiates
PCP
Explain the human chorionic gonadotropin (hCG) urine test
hCG is made by placenta, urine hCG concentration is much lower than serum and require higher level to detect. Serum test can detect as early as 6 days after ovulation, but typically 8-10 days after ovulation.
urine test is qualititative positive/negative pregnancy.
Can also screen for birth defects (quantitative) by the amount that hCG goes up early in pregnancy.
hCG may also be made by certain tumours, especially from egg/sperm, uterine, or testicles.
Microscopic urinanalysis abnormalities
RBCs- hematuria- kidney stones, malignancy, glomerular disease
WBCs- neurtrophils commonly associated with bacteriuria, interstitial nephritis, renal TB, nephrolithiasis
Eosinophils commonly associated with acute interstitial nephritis
Epithelial cells= contamination by genital secretions
Casts and crystals
Distinguish between -emia and -osis
-emia is a state of being (pH)
-osis is a process that is occurring
Discuss the effects of albumin on anion gap
Albumin is the most prevalent unmeasured anion. Normal/standard is 40g/L, use if unmeasured. When albumin is measured, for every 10 points dropped from standard, add 3 to anion gap.
How do you calculate anion gap
AG= (na+) - [(Cl-) + (HCO3-)] + albumin compensation
Normal is 8-12 (10 +-2)
Define KULT as it pertains to evaluation of metabolic acidosis
AGMA causes Ketones, Uremia, Lactate, Toxins
Lost the causes of NAGMA
GI losses- diarrhe, pancreatic or biliary fistula
Hyperchloremia
Renal tubular necrosis (loss of bicarb leads to acidosis)
List the causes of respiratory acidosis OR alkalosis
CNS or cardiopulmonary
List the causes of metabolic alkalosis
Cl- sensitive
- volume depleted, cells contracted
- loss of H+ (vomiting)
- responsive to tx
Cl- resistant
- H+ gone intracellular (HypoK, bicarb admin)
-retaining hco3- (renal)
- Tumor/infection stimulating aldosterone which stimulates HCO3- réabsorption
