Chemistry Specimen Processing

Separate serum/plasma from blood cells within 2 hours

• For serum, need to wait for specimen to clot first (20-30 min)

Store samples at 4C when not being run

For longer-term storage, store at minimum -20C

Analyte	Specimen Type	Collection Media	Collection Notes	Reference Interval
Sodium		Lithium heparin		135 - 145 mmol/L
Potassium		Lithium heparin		3.5-5.0 mmol/L
Glucose	Fasting			4.1 - 5.6 mmol/L
	Random
Creatinine	Urine, 24 hour
	Blood serum	Lithium heparin
Serum Iron
Ferritin
Total Iron Binding Capacity
% Transferrin Saturation				20-55%
Urea	Blood serum or plasma	Lithium heparin		2.1 - 7.1 mmol/L
	Urine, random		Use thymol preservative and refrigerate
	Urine, 24 hour		Use thymol preservative and refrigerate	430 - 710 mmol/day
Uric Acid	Blood serum or plasma	Lithium heparin
	Urine, 24 hour
Urinalysis	Urine, first morning midstream clean-catch preferred		Fresh samples <2h old

Special Samples:

• Keep on ice
  • Blood gases
  • Ammonia
• Protect from light
  • Bilirubin
  • Vitamin B12

Lab Test Reference Intervals

Test	Reference Interval	↑ Conditions	↓ Conditions	Interferences	Notes
Sodium	135 - 145 mmol/L	Hypernatremia
Potassium	3.5 - 5.0 mmol/L			↑↑↑ Hemolysis
Chloride
Bicarbonate
Anion Gap	10 - 20 mmol/L	Ketoacidosis (diabetes, starvation) Renal failure Lactic acidosis Hypernatremia Poisoning (methanol, ethanol, ethylene glycol, salicylates)	Rare Hypoalbuminemia Severe hypercalcemia
pH
pO2
pCO2
[HCO3-]
Glucose, fasting	4.1 - 5.6 mmol/L
Glucose, random
Total Bilirubin
Unconjugated Bilirubin
Conjugated Bilirubin
eGFR	>2.0 mL/s				Preferred over creatinine clearance
Urine flow rate	0.05 mL/s
Creatinine (serum)	62 - 115 μmol/L (male) 53 - 97 μmol/L (female)			↑ Hemolysis ↓ Icterus ↓ Lipemia Ammonium heparin Non-specific chromogens
Creatinine (urine, 24h)	9 - 18 mmol/d (male) 7 - 16 mmol/d (female)				Inaccuracies may arise from improper urine measurement or tubular secretion.
Creatinine Clearance	1.42 - 2.08 mL/s (male) 1.24 - 1.92 mL/s (female)				<0.63 mL/s is markedly decreased High serum creatinine may over-estimate CC.
C-reactive protein	<10 mg/L

Blood Gas Results

Test	Reference Interval	Clinical Relevance	Notes
Sodium	135 - 145 mmol/L
Potassium	3.5 - 5.0 mmol/L
Chloride
pH	7.35 - 7.45
pO2
pCO2	35 - 45 mmHg
[HCO3-]	21 - 28 mmol/L

Heme -> bilirubin -> unconjugated bilirubin (transport via albumin) -> conjugated bili -> urobilinogen (in GI) -> urobilin excreted

Hepatic Jaundice

• ↑ AST, ALT, GGT
• ALP N/↑
• ↑ Total, unconj., conj. bilirubin

Obstructive (post-hepatic) jaundice

• ↑↑ ALP and GGT
• ↑ Bilirubin
• ALT, AST vary

Enzymes

• ALT most liver specific
  • Except alcoholic cirrhosis AST 2x ALT
• AST more general (liver, skeletal muscle, heart, RBCs)
• GGT sensitive to liver injury, but not specific (high in alcoholic liver cirrhosis)
• LD not specific
• ALP non-specific
• ↓ albumin, ↑ gamma globulins (IgG, IgM hepatitis; IgA alcoholic cirrhosis)
  • Beta-gamma bridging

Pancreatitis

• Amylase
• Lipase (more specific than amylase)

Affected by HIL

• K⁺
• LD very sensitive!!! and unstable!!!
• AST
• Bilirubin
  • ↓ Hemolysis
  • ↑ Lipemia

Less Affected

• Na (dilutional effect)
• Cl (dilutional effect)
• ALP
• CK (gross hemolysis false ↑)

CSF Tubes

1. Chemistry
2. Microbiology
3. Hematology
4. Other (e.g., cytology)

Hashimoto = low T3,T4 and high TSH

Grave's = hyperthyroidism = excess T4, low TSH

Cushing's = high cortisol =

• High ACTH with ACTH-dependent (pituitary)
• Low ACTH with independent (adrenal cancer, etc.)
• Higher part of the body is high ACTH and dependent (pituitary); lower part of the body is low ACTH and independent (adrenal)

Cardiac Markers

• Myoglobin = earliest marker (but declines quickly)
• CK elevated in cardiac and skeletal disorders
  • CK-MB/CK2 most specific isoenzyme for cardiac issues (but also skeletal)
• Cardiac troponin 1 is very cardiac-specific!
  • High sensitivity cTnI used for investigating heart attacks
  • Detectable quickly (3-12 hours), and remain elevated >1 week
• NT-proBNP elevated in heart failure
• CRP acute marker of inflammation, can help evaluate risk for CVD