TYPE OF SPECIMEN - LAB

• Specimen collection


  The first step in clinical chemistry analysis, the accuracy and precision of the analyte can be measured by the proper ways of the specimen collection and the techniques of handling it
• Types of specimens analyzed in the clinical chemistry laboratory

  • Blood
  • Urine
  • Cerebrospinal fluid (CSF)
  • Other specimens (ascitic fluid, peritoneal fluid, etc.)
• Whole blood


  Plasma + Formed Elements
• Serum


  Liquid portion of the clotted blood, contains albumin and globulin
• Plasma


  Liquid portion of the unclotted blood, contains albumin, globulin and fibrinogen
• 24-hour urine sample


  Patient continuously collects urine sample within a 24-hour span (starts and ends at 7am)
• Random urine sample


  Used to confirm diabetes through glucose presence in urine
• Timed urine sample


  Used for various tests
• Cerebrospinal fluid (CSF)


  Used in tests like meningitis confirmation, to calculate lactate, glucose and protein
• Serum


  • Preferred specimen in Clinical Chemistry because certain substances like the lipemia clearing factor (LPL) are co-precipitated during clotting, it is clearer than plasma, and there is potential interference produced by anticoagulants
• Timing of specimen collections

  • Fasting (NPO - nothing by mouth)
  • Random
  • 24 hour
  • Postprandial (after meal)
• Classification of methods as to sample requirements

  • Macro method (blood sample 1 mL and above)
  • Micro method (blood sample 0.1 - 0.9 mL)
  • Ultramicro method (blood sample 0.01 - 0.09 mL)
  • Nanoliter method (blood sample 0.001 - 0.009 mL)
• Patient preparation


  Patients must be given correct instruction on how to prepare for each laboratory test, to minimize factors that may influence laboratory results
• Factors contributing to the variations of results


  • Exercise
  • Fasting
  • Diet
  • Posture/Position
  • Tourniquet application
  • Tobacco smoking
  • Alcohol ingestion
  • Stress
  • Drugs
  • Physiologic variation
• Immediate effects of exercise

  Elevated lactate, alanine, fatty acids
• Long-lasting effects of exercise

  Increased activity of muscle enzymes (AST, CPK, LDH, ALD), elevated concentration of sex hormones (testosterone, luteinizing hormone)
• Fasting duration


  1. 10 hours for glucose, 10-12/14 hours for lipid profile
• Fasting


  Elevated blood glucose, potassium and lipids like cholesterol and neutral fats, decreased inorganic phosphorus
• Prolonged fasting


  Elevations in serum bilirubin, plasma triglycerides, glycerol, free fatty acids, decrease in plasma glucose
• Diet


  Increases potassium and triglycerides, increases ALP activity 2-4 hours after fatty meal, increases urea, ammonia and urates with no significant increase in creatinine with high protein diet, increases urinary excretion of 5-HIAA with serotonin, increases concentration of non-esterified fatty acids with caffeine
• Lipemia


  Increases turbidity or lactescence, affects determinations like BCG method (albumin), O-Cresophthalein Complexone method (calcium), Acid ammonium molybdate procedure (inorganic phosphorus), decreases activity of AMS, CPK, urease and uricase, decreases levels of bilirubin, increases levels of total protein
• Remedy for lipemia


  Ultracentrifugation, blank technique
• Posture/Position


  Upright position or supine (lying) preferred, patient should be seated/supine for at least 20 minutes before blood collection to prevent hemodilution or hemoconcentration
• Changing from supine to sitting/standing

  Causes constriction of blood vessels and reduction of plasma volume - increased levels of albumin, enzymes and calcium
• Changing from sitting to supine

  Causes shifting of water and electrolytes into tissue causing hemoconcentration - increased levels of proteins, lipids, BUN, iron and calcium
• Changing from standing to supine

  Causes extravascular water transfer to the vascular system and dilutes non-diffusable plasma constituents - decreased levels of cholesterol, triglycerides and lipoproteins
• Prolonged bedrest


  Decreased plasma albumin due to fluid retention
• Tourniquet application


  One-minute application recommended, prolonged application results in hemoconcentration (venous stasis) and anaerobiosis
• Prolonged tourniquet application


  Increases levels of proteins (albumin), enzymes, lactate, cholesterol, potassium, NH3
• Tobacco smoking


  Increases plasma non-esterified fatty acid (NEFA) concentration, plasma catecholamines and serum cortisol, glucose, growth hormone, cholesterol, triglyceride and urea
• Alcohol ingestion


  Increases plasma concentration of urate and triglyceride, increases gamma glutamyl transferase (GGT) concentration, causes hypoglycemia (chronic alcoholism)
• Stress


  Affects adrenal hormone secretion, associated with increased levels of albumin, glucose, insulin, lactate and cholesterol, results in hyperventilation affecting acid-base balance
• Drugs


  Medications affecting plasma volume can affect protein, BUN, iron and calcium concentrations, hepatotoxic drugs can elevate liver function enzymes, diuretics can decrease plasma sodium and potassium levels
• Physiologic variation


  Changes that occur within the body such as cyclic changes (diurnal or circadian) or those resulting from exercise, diet, stress, gender, age, drugs, posture or underlying medical conditions
• Diurnal variations


  • ACP, iron, hormones (cortisol, ACTH, aldosterone, growth hormone, insulin, thyroxine, prolactin)
• Immediate local complications of venipuncture

  • Localized hemoconcentration or venous stasis
  • Syncope or fainting
  • Failure of blood to enter the syringe
• Local delayed complications of venipuncture

  • Thrombosis of veins
  • Thrombophlebitis
  • Hematomas
• General late complications of venipuncture

  • Serum hepatitis
  • AIDS
• Anticoagulants


  Chemical agents used to prevent coagulation or clotting of blood
• Types of anticoagulants


  • Oxalates
  • Citrates
  • EDTA
  • Fluoride
  • Heparin