PRE ANALYSIS

• Preanalysis


  All the complex steps that must take place before a sample can be analyzed
• 32%-75% of all testing errors occur in the preanalytic phase
• Preanalytic factors


  • Patient-related variables (diet, age, sex, etc.)
  • Specimen collection and labeling techniques
  • Specimen preservatives and anticoagulants
  • Specimen transport
  • Processing and storage
• 10 most common errors associated with specimen collection

  • Misidentification of patient
  • Mislabeling of specimen
  • Short draws/wrong anticoagulant/blood ratio
  • Mixing problems/clots
  • Wrong tubes/wrong anticoagulant
  • Hemolysis/lipemia
  • Hemoconcentration from prolonged tourniquet time
  • Exposure to light/extreme temperatures
  • Improperly timed specimens/delayed delivery to laboratory
  • Processing errors: Incomplete centrifugation, incorrect log-in, improper storage
• Errors in the preanalytic stage create rework or additional investigation that may cause unnecessary procedures for patients and costs to the health care system
• Proper collection technique is essential to minimize injury to the phlebotomist and the patient
• Physiologic factors


  • Diurnal variation
  • Exercise
  • Diet
  • Stress
  • Posture
  • Age
• Diurnal variation


  May be encountered when testing for hormones, iron, acid phosphatase, and urinary excretion of most electrolytes
• Exercise


  • Transient changes may include an initial decrease followed by an increase in free fatty acids, and lactate may increase by as much as 300%
  • Long-term effects of exercise may increase CK, aldolase, AST, and LD values
• Diet


  • Can greatly affect laboratory test results
  • Eating a meal, depending on fat content, may elevate plasma potassium, triglycerides, alkaline phosphatase, and 5-HIAA
  • Certain foods or diet regimens may affect serum or urine constituents
• Stress


  • Induces the production of ACTH, cortisol, and catecholamines
  • Total cholesterol has been reported to increase with mild stress, and HDL cholesterol may decrease
• Posture


  • An upright position increases hydrostatic pressure, causing a reduction of plasma volume and increased concentration of proteins
  • Incorrect application of the tourniquet and fist exercise can result in erroneous test results
• Age


  • Newborn: Much of the Hb is Hb F, not Hb A, as seen in the adult
  • Childhood to puberty: Serum alkaline phosphatase and creatinine levels increase with skeletal growth and muscle development
  • Adult: Most serum constituents remain constant
  • Elderly adult: Most serum constituents remain constant
• Preanalysis


  Avoiding changes in diet, alcohol consumption, and strenuous exercise 24 hours before having blood drawn for laboratory testing
• Age


  • Affects serum constituents
  • Newborn, childhood to puberty, adult, and elderly adult are the four age groups
  • In newborns, much of the hemoglobin is Hb F, not Hb A
  • Bilirubin concentration rises after birth and peaks at about 5 days
  • Infants have a lower glucose level than adults due to low glycogen reserve
  • Skeletal growth and muscle development increase serum alkaline phosphatase and creatinine levels
  • Uric acid level decreases for the first 10 years of life, then increases, especially in boys, until age 16
  • Most serum constituents remain constant during adult life until menopause in women and middle age in men
  • Cholesterol and triglycerides increase until midlife
  • Uric acid levels peak in men in their 20s but not until middle age in women
  • The elderly secrete less triiodothyronine, parathyroid hormone, aldosterone, and cortisol
  • After age 50, men experience a decrease in testosterone secretion rate and concentration, and women have an increase in pituitary gonadotropins, especially FSH
• Gender


  • Men generally have higher alkaline phosphatase, aminotransferase, creatine kinase, and aldolase levels than women due to larger muscle mass
  • Women have lower levels of magnesium, calcium, albumin, hemoglobin, serum iron, and ferritin due to menstrual blood loss
• Pseudohyperkalemia can occur in patients with extremely high blast counts in acute or accelerated phase leukemias due to fragile blasts lysing during standard phlebotomy and releasing potassium
• Specimens with very high WBC counts that are collected gently can show pseudohypokalemia when potassium is taken up by highly metabolically active leukemic cells along with glucose
• Normally platelets release potassium during clotting, so serum has a slightly higher value of potassium than plasma from the same individual, and this difference is accentuated when the platelet count is extremely elevated
• To avoid problems with hemoconcentration and hemodilution


  1. The patient should be seated in a supine position for 15 to 20 minutes before the blood is drawn

  2. Extended application of the tourniquet can cause hemoconcentration, which increases the concentrations of analytes and cellular components
• When blood collection tubes with anticoagulants/additives are used

  1. Follow the proper order of draw

  2. Thoroughly mix an anticoagulated tube of blood after it has been filled

  3. Failure to mix a tube containing an anticoagulant will result in failure to anticoagulate the entire blood specimen, and small clots may be formed
• Erroneous cell counts can result if a clot is present, as it may occlude or otherwise interfere with an automated analyzer
• It is very important that the proper anticoagulant be used for the test ordered, as using the wrong anticoagulant will greatly affect the test results
• Each collection tube containing an anticoagulant has a specific manufacturer's color code
• Icteric or lipemic serum


  • Provides additional challenges in laboratory analysis
  • When serum bilirubin approaches 430 mmol/L (25 mg/L), interference may be observed in assays for albumin, cholesterol, and total protein
  • Elevated triglyceride levels (turbidity) can result in artifactually induced values in some laboratory determinations
• To correct for artifactual absorbance readings

  1. Blanking procedures or dual-wavelength methods may be used

  2. Ultracentrifugation may be necessary to clear the serum or plasma of chylomicrons in some cases of turbidity
• One of the most frequent preanalytic errors involves selecting the wrong laboratory test or panel of tests, leading to inappropriate interpretation of results
• In vivo


  Changes that occur in the body, such as from tobacco smoking
• Tobacco smokers


  • Have high blood carboxyhemoglobin levels, plasma catecholamines, and serum cortisol
  • Changes in these hormones often result in decreased numbers of eosinophils, while neutrophils, monocytes, and plasma fatty free acids increase
  • Chronic effects of smoking lead to increased hemoglobin concentration, erythrocyte count, MCV, and leukocyte count
  • Increased plasma levels of lactate, insulin, epinephrine, and growth hormone and urinary secretion of 5-HIAA are also seen
  • Vitamin B12 levels may be substantially decreased and have been reported to be inversely proportional to serum thiocyanate levels
  • Smoking affects the body's immune response, with lower IgA, IgG, and IgM, and higher IgE levels
  • Decreased sperm counts and motility and increased abnormal morphology have been reported in male smokers
• In vitro


  Changes that occur during the collection and processing of the specimen
• Hemolysis


  • Can be caused by using a needle that is too small, pulling a syringe plunger back too fast, expelling the blood vigorously into a tube, shaking or mixing the tubes vigorously, or performing blood collection before the alcohol has dried at the collection site
  • Hemolysis can falsely increase blood constituents such as potassium, magnesium, iron, LD, phosphorus, ammonium, and total protein
• Level of hemolysis


  Affects the potassium concentration, with even low levels of hemolysis causing minor elevations and very strong hemolysis raising the potassium level by 2 to 3 mEq/L into a critical range
• Specimen rejection is costly and time-consuming, and can cause harm to the patient, especially when the blood sample in the tube is mislabeled
• The incidence of patient misidentification at the time of specimen collection is approximately 1 in 1000, and 1 in 12,000 patients receives a unit of blood that was not intended for that individual
• Reasons for specimen rejection

  • Inappropriate specimen type
  • Wrong preservative
  • Hemolysis
  • Lipemia
  • Clots
• Venipuncture


  Accomplished using a needle/adapter assembly attached to an evacuated glass/plastic test tube with a rubber/plastic stopper
• AccuVein


  A hand-held medical device that helps medical staff visualize veins before phlebotomy by emitting infrared light and projecting an image map of the veins onto the patient's skin
• Anticoagulants/additives in blood collection tubes

  • Based on color-coded tube stoppers
• AccuVein


  • Helps healthcare providers visualize patients' veins to guide blood collection and IV placement
• Anticoagulants/additives in blood collection tubes

  • Clot activator
  • K3EDTA in liquid form
  • K2EDTA/spray-dried
  • Spray-dried K2EDTA
  • EDTA and gel
  • Sodium citrate
  • Thrombin and soybean trypsin inhibitor
  • Lithium heparin and gel
  • Sodium heparin, lithium heparin
  • Sodium heparin, K2EDTA
  • Sodium fluoride/potassium oxalate
  • Sodium polyanetholesulfonate
  • Acid citrate dextrose
  • Sodium heparin
  • Thrombin
  • Clot activator separation gel