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Labs

Basic Metabolic Panel (BMP)

Liver (LFT)/Pancreas

Inflammatory Markers

Basic Metabolic Panel (BMP)

Na - 135-145mEq/L

Low Na expect and hope serum Osm to be low
- 2 [Na+] + [Glu]/18 + [BUN]/2.8
Hyponatremia
- Hypotonic hyponatremia (<280 mOsm)
  - Hypovolemic
    - Diuretics, Addison, diarrhea, vomitting
  - Euvolemic
    - SIADH, adrenal insufficiency, hypothyroid
  - Hypervolemic
    - CHF, hypoprotein (think edema)
- Isotonic hyponatremia (280-290 mOsm)
  - Could be hyperlipidemia/lab artifact
- Hypertonic hyponatremia (>295 mOsm)
  - Hyperglycemia
Hypernatremia
- Hypovolemic hypernatremia
  - GI loss, burns, 3rd space, diuretics, dehydration
- Euvolemic hypernatremia
  - DI/NDI
- Hypervolemic hypernatremia
  - Cushing, hyperaldosterone, too much saline

K - 3.5-5mEq/L

Hypokalemia
- GI loss
- Endo: hypercortisol, hyperaldo
- Intracellular shift
  - hypoOsm, Alkolosis
  - Insulin, thyrotoxicosis
- Renal loss (↑ excretion)
  - Loop/thiazide diuretics
- ↓ intake
Hyperkalemia
- Cell destruction (rhabdo, hemolysis)
- Endo: hypocortisol, hypoaldo
- Extracellular shift
  - hyperOsm, Acidosis
  - ↓ insulin (from ↑ BG)
- Renal gain (↓ excretion)
  - ACEi/ARB, K sparing diuretics, acute/CKD
- β-blockers, digoxin

Cl - 95-105mg/dL

Hypochloremic
- Metabolic alkalosis
  - Lost Cl ➔ ↑ HCO3 to compensate
    - Vomiting, diuretics
- Chronic respiratory acidosis
Hyperchloremic
- Normal anion gap acidosis (hyperchloremic)
  - Lost HCO3 ➔ ↑ Cl to compensate
    - Diarrhea, Addison, renal tubular acidosis
- Dehydration

Bicarb 22-28mEq/L

Decreased bicarb
- Metabolic acidosis/Compensated respiratory alkalosis
Increased bicarb
- Metabolic alkalosis/Compensated respiratory acidosis

BUN

Decreased BUN can be from severe liver dz
Increased BUN: ↓ GFR ➔ ↑ BUN
- > 20:1 BUN/Cr - pre-renal AKI
- <15:1 BUN/Cr - intra-renal
- Dehydration, ↓ perfusion ➔ ↑ urea reabsorption

Creatinine

Indirect measure of kidney function (only when GFR < 60)
Serum Cr ↑ when GFR ↓ by 50%

Elevated BUN without AKI (↑ in Cr)

GI bleeding (digested blood ➔ ↑ N)
↑ protein intake, TPN, catabolism, steroid use

Glucose ~ 65-100

CMP BMP + Ca, Albumin/total protein, LFTs

Albumin - 3.4-5.4 g/dL

Hyperalbuminemia - Dehydration
Hypoalbuminemia - Cirrhosis, nephrotic syndrome, inflammation, malnutrition

Calcium - 8-10 mg/dL (bound) or 4.0-5.6 (ionized)

Hypocalcemia
- with ↓ PTH - 1 ° HypoPTH (post-surgical or autoimmune)
- with ↑ PTH - vit D deficiency
- PsuedohypoPTH/hyperphosphatemia (↑ PO4)
- CKD (↑ PO4, ↑ creatinine) Malabsorption (↓ Mg)
Hypercalcemia
- with ↓ PTH - vit D intoxication
- with ↑ PTH - 1 ° hyperPTH (↓ PO4); ↑ urine Ca

Ca is a cation and binds negatively charged albumin

If there is less albumin... there is "less" bound Ca ➔ false lower Ca level
In other words, in hypoalbuminemia, there is more Ca present than measured
- Use corrected calcium (or ionized Ca) if albumin < 4.0: [Ca] + 0.8(4.0 - albumin)

CBC

Coagulation

PT/INR - 11-15s

Common and extrinsic
Vit K antagonist (warfarin) monitoring
Elevated in in Vit K deficiency

aPTT - 25-40s

Common and intrinsic
UF heparin monitoring
Elevated in Vit K deficiency, hemophilia, SLE

BT - 2-7m

Primary hemostasis
↑ in thrombocytopenia

D-dimer - < 0.5 mcg/mL

Fibrin degradation
↑ in DVT, PE, DIC

Iron Studies

Sr Fe

Free, circulating Fe
LOW : Fe deficiency, Anemia of chronic dz/chronic inflammation
HIGH: Fe overload, Sideroblastic anemia

Ferritin

Fe storage protein - best indicator of Fe deficiency
LOW: Fe deficiency
HIGH: Fe overload, Anemia of chronic dz/chronic inflammation, Sideroblastic anemia

Transferrin/TIBC

Fe transport
LOW: Fe overload, Anemia of chronic dz/chronic inflammation, Sideroblastic anemia
HIGH: Fe deficiency

Transferrin saturation TfS

How much Fe bound
LOW: Fe deficiency (because: ↓ Fe/transferrin)
HIGH: Fe overload (because: ↑ Fe/transferrin)

Fe overload

↓ RBC production or ↑ destruction
- Thalassemia
- Hemochromatosis
- X transfusions
- Supplements

Fe deficiency

Pregnancy, bleeding, malnutrition
- ↓ Fe, ↓ Ferritin, ↓ TSAT
  - depleted stores
- ↑ Transferrin/TIBC
  - floating around looking for more Fe

Anemia of chronic dz

- ↑ hepcidin ➔ ↓ Fe absorption
- ↓ Fe, ↓ Transferrin, ↓ TSAT
- ↑ Ferritin
  - storing but not using

Thyroid Labs

Cardiac Labs

Troponin T/I (Specific/sensitive)

Seen: 1-3hr (rapid); 6hrs (regular)
Peaks:12-24hrs
Normal in: 1 week
Cleared by kidneys (remains elevated in CKD pts)

CK-MB

Seen: 4-6hrs
Peak: 12-24hrs
Normal in: 2-3d

Myoglobin (Fastest)

Seen: 1-4hrs
Peak: 6hrs
Normal in: 1d

proBNP

Precursor: ↑ in LV wall stretch (↑ in HF)

BNP (B-type natriuretic peptide)

Biologically active
- Causes natriuresis, diuresis
- Vasodilation
- ⊣ renin & aldosterone
- BNP ↑ with entresto

NT-proBNP (N-terminal pro-BNP)

"Inactive" - used as a marker of ↓ wall stress in pts takin entresto

Liver (LFT)/Pancreas

ALT/AST

Gluconeogenesis, urea generation, AA metabolism
AST (normal is < 35); ALT (normal is < 45)
Increased in: Hepatocyte damage
AST < ALT: inflammatory
- Viral hepatitis
- Extra-hepatic cholestasis
- Fatty liver
AST > ALT: necrotic
- EtOH/fulminant hepatitis
- Cirrhosis

GLDH

Liver specific - Hepatocellular carcinoma, liver METS

Albumin

Maintains colloid osmotic pressure, transport protein
- Pre-albumin is best indicator of nutritional status
Increased in: Dehydration
Decreased in: Cirrhosis, nephrotic syndrome, malnutrition

Alkaline phosphatase ALP

Biliary (check to make sure GT ↑) and bones
↑ in cholestasis, 3rd trimester, CKD

GT, GGT

High sensitivity for liver dz but not specific
Confirms ↑ ALP not from ↑ osteoblast activity
↑ in cholestasis

Bilirubin

Total bilirubin - Direct bilirubin = In-direct bilirubin

Total bilirubin

Abnormal T.bili ➔ order D.bili to get indirect bili

In-direct bilirubin

Un-conjugated - lipophilic
Increased: Pre-hepatic (hemolysis/hematoma reabsorbed) ➔ ↑

Direct bilirubin

Conjugated - water soluble
Increased: Post-hepatic (biliary system obstruction)

Amylase/Lipase

Acute pancreatitis ➔ ↑ more than 3x
- Lipase more pancreas specific than amylase
Can go up with gallbladder
Amylase can ↑ with salivary gland problems
Renal failure ➔ ↑ (↓ excretion)

Elastase

Acute pancreatitis ➔ ↑ in serum
Exocrine pancreatic insufficiency (cystic fibrosis, chronic pancreatitis) ➔ ↓ in stool

CSF

BX

WBC: > 1,000
- (↑ PMN)
Glucose: < 40 (low)
Protein: > 250 (high)

Viral

WBC: 5-1,000
- (↑Lymphocytes)
Glucose: 50-80 (normal)
Protein: < 100 (normal/high)

Fungal

WBC: < 500
- (↑ Lymphocytes)
Glucose: 50-80 (normal/low)
Protein: > 250 (normal/high)

TB

WBC: 5-1,000
- (↑ Lymphocytes)
Glucose: < 10 (very low)
Protein: > 250 (normal/high)

Urinalysis

Color
Clarity
pH: 4.5–8
Urine specific gravity: urine density/pure water density (normally 1.005–1.030)
- 1.010-1.030 hints at dehydration
- High specific gravity: (more concentrated) volume loss, HF, glucose or radiocontrast in urine
- Low specific gravity: (dilute) renal failure, DI
Heme: hematuria dx requires microscopy
- Semen, myoglobin ➔ positive
- Vit. C in urine can ➔ false negative
Leukocyte esterase: hints at UTI
Protein: picks up gross albumin, not nephrotoxic light chain IG (like Bence Jones protein)
Glucose: DM ➔ glycosuria
Ketones: DKA
Urobilinogen:
- No urobilinogen in urine of jaundiced pt: complete biliary obstruction
- Increased urobilinogen: hemolysis, cirrhosis, hepatitis
Nitrite: UTI with gram neg bx MC Enterobacteriaceae

Sediment

RBC and WBC
Casts
- Can be normal finding or sign of serious renal issue
- Casts assume shape and size of renal tubule where they are formed
  - Hyaline casts - Nonspecific (CKD) or intense exercise
  - Granular cast - Acute tubular necrosis, pyelonephritis
  - Muddy brown casts - Acute tubular necrosis
  - Hemoglobin casts - Intravascular hemolysis
  - Fatty casts - Nephrotic syndrome
  - Renal tubular epithelial cell casts - Interstitial nephritis, proliferative glomerulonephritis
  - White blood cell casts - pyelonephritis
  - Red blood cell casts - glomerulonephritis
  - Waxy casts - Nonspecific AKD/CKD

Urine Culture

ASX pt: ≥10^5 CFU/mL
SX ♀ with pyuria ≥10^2/mL: indicative of a UTI

hCG

Human chorionic gonadotropin

β-hCG is placenta specific
- Urine hCG: ~ 14d after fertilization
- Serum hCG: ~ 6-9d after fertilization
Doubles every 2d first month, peaks at ~10-12wks
Embryo visible at 1,500-2000 (~5-6wks) and cardiac activity
Doppler US detects fetal heartbeat (~10-12wks)

TB skin test

Positive: active TB or latent TB
- ≥ 5 mm:
  - Close contact with TB
  - HIV infection/immunosuppressed
  - SX or x-ray showing active or prior TB
- ≥ 10 mm:
  - From high TB country (in last 5yrs)
  - High-risk (homeless/healthcare/IVDA)
  - DM/CKD
  - < 5yo
- ≥ 15 mm is considered positive in everyone else
If positive PPD - do CXR
- Chronic may have caseating granulomas
- Active has complexes in middle and lower
- Reactive has cavitary lesions in upper/apex

RIPE

Rifampin (RIF) 6mo
- Red/Orange secretions
- ⊣ oral BC, warfarin, digoxin, metformin
Isoniazid (INH) 6mo
- Give with pyridoxine (VIT. B6) to ↓ neuritis
Pyrazinamide (PZA) 2mo
- Hyperuricemia
- Photosensitive rash (after 1st trimester)
Ethambutol (EMB) 2mo
- Optic neuritis ➔ vision/color ∆ (D/C & switch to streptomycin)

Latent TB & Prophylaxis for household:
- Isoniazid with pyridoxine (1yr)

Cancer markers

Alphafetoprotein (AFP)

Liver, Testes, Ovarian
Produced by developing fetus liver
↑ in pregnancy and birth (↓ by 1yo)
Produced when liver cells regenerate
Hepatocellular carcinoma dx or monitor tx/recurrence
↑ in cirrhosis, hepatitis

CA 125

Ovarian/gynecologic, lymphoma
Good for following TX

CA 19-9

Pancreatic cancer

FIT/FOBT

Stool sample for occult blood (colorectal cancer) or R/O anemia
Screening: Annually at 50yo (40yo if 1st ° relative hx)
Get colonoscopy if positive (after r/o hemorrhoids)
- Can see "apple core lesion" on double barium
- CEA for monitoring/not screening

Inflammatory Markers

Complement C3, C4

Autoimmune, Inflammation

↑ immediately after infection/injury
↓ C4: rheum vasculitis, angioedema
↓ C3: membranoproliferative glomerulonephritis, septicemia, endocarditis
↓ C3 & C4: in SLE

ESR (Erythrocyte sedimentation rate)

HIGH ESR: ↑ fibrinogen (infxn, inflammation, cancers) ➔ RBC sinks faster
LOW ESR: RBC disorders, ↑ WBC, CHF ➔ RBC floats longer

Positive acute phase reactants (goes up with inflammation)

CRP (C-reactive protein)

Promotes opsonization (marks for phagocytosis) & activates compliment
Sensitive for inflammation but no specificity for specific dz

Fibrinogen

Promotes endothelial repair after insult (↑ fibrinogen ➔ ↑ ESR)

Procalcitonin

↑ as bx infxn ↑ (sepsis, PNA)

Ferritin

↑ ferritin ➔ ↓ free Fe (infxn, cancers)
↓ in pseudomonas infxn

Hepcidin

↑ hepcidin ➔ ↓ free Fe (inflammation) think anemia of chronic dz

Haptoglobin

↑ in infxn
↓ in hemolysis (binds free hemoglobin)

Negative acute phase reactants (goes down)

Albumin

Amino acids conserved for acute phase reactant production ➔ ↓ albumin

Transferrin

↓ transferrin ➔ ↓ Fe (infection)

Autoimmune

ANA (Anti-Nuclear-AB)

Autoimmune affecting connective tissue

Anti-dsDNA ➔ SLE (with anti-phospholipid)
Anti-RO/LA ➔ Sjögren (with RF)
Anti-Joa/Mi2 ➔ Polymyositis (with RF)

ANCA (Anti-Neutrophil Cytoplasmic AB)

Autoimmune ➔ Vasculitis, GI, Hepatic

c-ANCA ➔ Granulomatosis with polyangitis
p-ANCA ➔ Microscopic polyangitis
Atypical p-ANCA ➔ Primary sclerosing cholangitis, ulcerative colitis

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