Interpretation of Labs Flashcards
What is the most important and first thing that must be done prior to performing lab testing?
Obtain patient consent
Patient comes in with sluggish, altered mental state. What test helps distinguish if they have hypoglycemia or stroke & should be done ASAP?
Glucose check
What is the reasoning behind administering glucose as IVPB (IV piggy back)?
Gives body time to process glucose (not all at once)
Difference between CBC & CBC w/ diff?
CBC w/ diff = CBC + absolute differential counts (WBC breakdown)
What is tested in a BMP (chem 7)?
kidney fx, electrolytes, acid-base fluid balance
What is tested in a CMP?
BMP + LFTs + Mg + PO4 + Ca
Conditions indicated w/ leukocytosis (neutrophil predominance)
Bacterial infection, inflammation, neoplastic issue
Conditions indicated w/ leukocytosis (lymphocyte predominance)
Viral (EBV) / Bacterial (pertussis) infection, lymphocytic leukemia (ALL, MLL)
Conditions indicated w/ leukocytosis (basophilia)
Allergic rxn, hypothyroidism, splenectomy, neoplastic issue
Conditions indicated w/ leukocytosis (monocytosis)
GI issues, sarcoidosis, B. marrow suppression
Conditions indicated w/ leukocytosis (eosinophilia)
Parasitic infections, allergic rxns, GI issues, cutaneous issues
Conditions indicated w/ leukopenia (neutropenia)
Overwhelming bacterial infection, AIDS, hypersplenism, cachexia, anaphylactic shock
Conditions indicated w/ leukopenia
lymphopenia
immunodeficiency, excess adrenocortical/corticosteroid (exogenous/endogenous), HIV, lymphatic obstruction, cancer, chemo drugs
Condition indicated by RBC MCV < 80
microcytic anemia (iron deficiency, spherocytosis, chronic diseases)
Conditions indicated by RBC MCV > 100
macrocytic anemia (megaloblastic folate/B12 deficiency, anti-retrovirals)
Conditions indicated RBC low Hct
acute bleed
plasma volume need 12-24 hrs to equilibrate
Thrombocytopenia-related conditions associated with the following values:
- 50K-70K:
- <10K-20K:
- 50K-70K = clinical evidence of bleeding
2. <10K-20K = major spontaneous bleeding
When should a blood transfusion be considered?
Thrombocytopenia such that:
- <70K-100K w/ acute bleed OR
- <10K asymptomatic
Conditions indicated w/ thrombocytosis
Reactive or myeloproliferative disorder
Conditions associated w/ low glucose hypoglycemia
Fasting, excess insulin/sulfonylurea drugs. hepatic/renal/adrenal insufficiency, insulinomas
3 scenarios where BUN increases
Azotemias (Pre-renal, renal, post-renal)
Pre-renal: BUN/Cr > 10, hypovolemia (i.e. dehydration, cirrhosis)
Post-renal: BUN/Cr»_space; 10, obstructive uropathy
Renal: BUN/Cr < 10, kidney not excreting urea
What 2 measurements together determine volume status?
BUN & creatinine
2 scenarios where BUN decreases
Urea synthesis (liver disease, malnutrition)
Dilutional state (SIADH, 3rd trimester preg)
What does creatinine measure?
What does it mean if it’s elevated compared patient’s baseline?
Kidney/renal fx
Loss of renal fx
Conditions indicated with abnml Na+
Neurologic issues (i.e. seizures, trauma)
Define hypovolemic vs euvolemic vs hypervolemic hyponatremia (low Na)
Hypovolemic: GI / renal loss
Euvolemic: SIADH
Hypervolemic: congestive heart failure, cirrhosis, CKI
Causes of hypernatremia
Reduced H20 relative to Na (i.e. diarrhea)
Skin loss
Renal loss
Conditions indicated with abnml K+
Acid-base disorders that cause electrolyte shifts (DKA, sepsis, crush injuries, burns, etc.)
Importance of Cl-
Determines anion gap
Reason for hypercholeremia?
for hypocholeremia?
Hyper: non anion gap metabolic acidosis
Hypo: loss of body fluid, metabolic alkalosis
Importance of CO2
Determines cause of metabolic acidosis
Conditions indicated with abnml Ca2+
Cardiac dysrhythmias & electrolyte abnormalities
What is hypercalcemia associated w/
hyperparathyroidism or malignancy
What is hypocalcemia associated w/
hypoalbuminemia and hypomagnesemia
Conditions indicated with abnml Mg2+
Cardiac dysrhythmias, neuromuscular irritability, medication-induced electrolyte abnormalities
Conditions indicated with abnml PO4
Renal insufficiency, massive cell death (i.e. crush injury, hemolysis, tumor lysis, burns, etc.)
When to order LFTs?
Suspicion of liver inflammation, biliary obstruction, or hemolysis
What components are included in LFTs?
AST/ALT, Alk Phos, bilirubin
Where is ALT found? AST?
ALT: ONLY liver
AST: Liver, heart, blood, skeletal M.
Where is Alk Phos found?
liver, bone, intestine, and placenta
Typical causes of direct (conjugated) vs indirect (unconjugated) hyperbilirubinemia
Direct: Gilbert’s dz, blood issues (poor synthesis/lysing)
Indirect: hepatic failure
When to order lipase/amylase?
suspicion of pancreatitis
Typical cardiac enzymes included in cardiac panel
- Troponin I
- BNP
- D-Dimer
When to order Troponin I
Evaluate myocardial cellular damage (i.e. MI or myocardial ischemia) - detected in bloodstream 1-6 hrs after onset of chest pain
When to order BNP
Distinguish primary pulmonary causes of dyspnea from cardiac causes, >400 suggests heart failure
When to order D-Dimer
Rule out DVT or PE in low risk patients
When to order serum lactate
Confirm shock, Indications of hypoxic tissue, metabolic disorders (i.e. metabolic acidosis), toxin exposure
When to order coagulation studies (INR/PT, PTT)
- Evaluate patients on heparin & warfarin anticoagulants
- PT for coumadin, PTT for heparin - Establish baseline of active bleeding patients
- Evaluate clotting disorders
Presence of nitrates, leukocyte esterase, WBC’s, and bacteria in UA indicates
UTI
Common drugs screened for w/ urine toxicology?
Amphetamines, cocaine, benzodiazepines, barbiturates, opiates, marijuana, and PCP
When to order Fecal Occult Blood Test (FOBT)
When NOT to order Fecal Occult Blood Test (FOBT)
order: detect hidden (occult) blood loss in stool
don’t order: rectal bleeding in patient hx or gross blood on digital rectal exam
Characteristics of heme FOBT
cheap, fast, less sensitive
Characteristics of globin FOBT
expensive, slower, more sensitive
Situations that give FOBT false negative.
Situations that give FOBT false positive
false - : high vitamin C
false + : red meat, peroxidase-rich veggie consumption
When to order TSH/T4?
Diagnose hypothyroidism (levels would be low)
When to order arterial blood gas (ABG)?
assess ventilation, perfusion, acid-base status
What does ethanol (EtOH) level of 80 mg/dl indicate?
How about >400?
80 = impairment for driving >400 = fatal
Phases of aspirin (ASA) toxicity
Early respiratory alkalosis followed by late respiratory acidosis
Elevated acetone (aka ketone) indicates
DKA, starvation, isopropanol ingestion
When to order CRP?
Detect chronic inflammatory disorders & cardiac risk
When to order C-diff toxin?
Detect antibiotic-associate diarrhea and pseudomembranous coli
When to order sputum (gram stain)?
Identify organism causing lung/upper airway infection
When to order monospot?
Confirm mononucleosis caused by Epstein-Barr Virus (EBV) infection
What does Inf A/B test for?
Influenza A/B strains
What is ESR?
Acute phase reactant that indicates inflammation or serious underlying disease when elevated