Clinical Laboratory Tests and Procedures

BLOOD BANK

  • Also known as .
  • Section of the laboratory where blood may be collected, stored, and prepared for transfusion.
  • In the blood bank, blood from patients and donors is tested for its blood group (ABO) and Rh type, the presence and identity of abnormal antibodies, and its compatibility (crossmatch) for use in a transfusion.
  • Units of blood are collected from donors, tested for the presence of blood-borne pathogens, and stored for transfusions.
  • Donor blood may also be separated into components (e.g. packed RBC’s (pRBC’s), Fresh Frozen Plasma (FFP), platelets etc.).
  • These components are stored separately and used for patients with specific needs.

ABO BLOOD GROUP

  • Red blood cell types:
    • Group A
    • Group B
    • Group AB
    • Group O
  • Antigens and Antibodies:
    • Group A: A antigens, Anti-B antibodies
    • Group B: B antigens, Anti-A antibodies
    • Group AB: A and B antigens, No antibodies
    • Group O: No antigens, Anti-A and Anti-B antibodies

BLOOD BANK

Sample Collection and Handling of Blood for Blood Bank Tests
  • SAMPLE OF CHOICE: ___.
  • ANTICOAGULANT OF CHOICE: ___.
  • INVERSION: ___.
  • Patient identification is critical in the blood bank, and phlebotomists must carefully follow all patient identification and sample labeling procedures to ensure that the patient does not receive a transfusion with an incompatible blood type.

BLOOD BANK

Tests Performed in the Blood Bank Section
  • Antibody (Ab) screen (Indirect Antiglobulin Test): Detects abnormal antibodies in serum.
  • Direct antihuman globulin test (DAT) or Direct Coombs: Detects abnormal antibodies on red blood cells.
  • Blood Group and type: ABO and Rh typing.
  • Panel: Identifies abnormal antibodies in serum.
  • Type and crossmatch (T & C): ABO, Rh typing, and compatibility test.
  • Type and screen: ABO, Rh typing, and antibody screen.

SEROLOGY

  • The serology (immunology) section performs tests to evaluate the body’s immune response; (production of antibodies) and cellular activation.
  • Most test performed in this section detects the presence of antibodies in serum, thus the section is frequently called serology rather than the broader term immunology.
  • Tests in the serology section detect the presence of antibodies to bacteria, fungi, parasites, viruses and antibodies produced against body substances (autoimmunity).

SEROLOGY

Sample Collection and Handling of Blood for Serological Tests
  • SAMPLE OF CHOICE: ___.
  • ANTICOAGULANT OF CHOICE: ___.
  • ___ are not used when the gel will interfere with the antigen-antibody reactions.

SEROLOGY

Tests Performed in the Serology Section
  • Anti-HIV: Screening test for human immunodeficiency virus.
  • Antinuclear antibody (ANA): Detects nuclear autoantibodies.
  • Antistreptolysin (ASO) screen: Detects a previous Streptococcus infection.
  • C-reative protein (CRP): Elevated levels indicate inflammatory disorders.
  • Cold agglutinins: Elevated levels indicate atypical (Mycoplasma) pneumonia.
  • Complement levels: Evaluate the function of the immune system.
  • Cytomegalovirus antibody (CMV): Detects cytomegalovirus infection.
  • Fluorescent treponemal antibody-absorbed (FTA-ABS): Confirmatory test for syphilis.
  • Hepatitis A antibody: Detects hepatitis A current or past infection.
  • Hepatitis B surface antigen (HBsAg): Detects hepatitis B infection.
  • Hepatitis C antibody: Detects hepatitis C infection.
  • Human chorionic gonadotropin (HCG): Hormone found in the urine and serum during pregnancy.
  • Immunoglobulin (lgG, lgA, lgM) levels: Evaluate the function of the immune system.
  • Monospot: Screening test for infectious mononucleosis.
  • Rapid plasma reagin (RPR): Screening test for syphilis.
  • Rheumatoid arthritis (RA): Detects autoantibodies present in rheumatoid arthritis.
  • Venereal Disease Research Laboratory (VDRL): Screening test for syphilis.
  • Western blot: Confirmatory test for human immunodeficiency virus.

MICROBIOLOGY

  • This is responsible for identification of pathogenic microorganisms and for hospital infection control.
  • The section may be divided into bacteriology, mycology, parasitology, and virology.
  • In bacteriology, identification of bacteria is based on morphology, Gram stain reactions and biochemical reactions.
  • This is followed by a culture and sensitivity (C & S) test that is used to detect and identify microorganisms and to determine the most effective antibiotic therapy.
  • In mycology, fungi are identified primarily by culture growth and microscopic morphology.
  • In parasitology, the main procedure performed is fecalysis where stool samples are concentrated and examined microscopically for the presence of parasite, ova, or larvae.
  • In the virology section, viruses must be cultured in living cells and tissues because they are considered obligate intracellular pathogens.

MICROBIOLOGY

Sample Collection and Handling of Blood for Microbiology Tests
  • Most microbiology samples are obtained from the blood, urine, throat, sputum, wound, CSF and feces.
  • Correct identification of pathogens depends on proper collection and prompt transport to the laboratory.
  • Phlebotomists are responsible for collecting blood cultures and may be required to obtain throat cultures & instruct patients in the procedure for collecting urine, sputum & other samples for culture.
  • Specific sterile techniques must be observed in the collection of culture samples to prevent bacterial contamination.

MICROBIOLOGY

Tests Performed in the Microbiology Section
  • Acid-fast bacillus (AFB) culture: Detects acid-fast bacteria, including Mycobacterium tuberculosis.
  • Blood culture: Detects bacteria and fungi in the blood.
  • Culture and sensitivity (C & S): Identifies pathogen causing the infection & determines antibiotic treatment.
  • Fungal culture: Detects the presence fungi & determines the type of fungi.
  • Gram stain: Detects the presence of bacteria and aids in the identification of bacteria.
  • Occult blood: Detects non-visible blood (performed on stool samples).
  • Ova and parasites (O & P) (Fecalysis): Detects parasitic infection (performed on stool samples).

URINE ANALYSIS

  • Urinalysis (UA) is a routine screening procedure to detect disorders and infections of the kidney and to detect metabolic disorders such as diabetes mellitus and liver disease.
  • A routine UA consists of physical, chemical, and microscopic examination of urine.

CLINICAL MICROSCOPY

Sample Collection and Handling of Blood for Urinalysis Tests
  • Random samples are most frequently collected for routine screening; however, a first morning sample is more concentrated and may be required for certain tests.
  • Other types of urine samples include timed or 24-hour collections for quantitative tests, midstream clean-catch and catheterized samples for cultures.
  • The phlebotomist may be requested to deliver urine samples to the laboratory.
  • This should be done promptly because many changes can take place in the urine sample that sits at room temperature for longer than 2 hours.
  • If a single sample has two requests (e.g. urinalysis and urine culture), the sample must be delivered first to the microbiology section before urinalysis is performed to avoid contamination.

CLINICAL MICROSCOPY

THREE PHASES OF URINALYSIS
  1. Physical Examination of Urine
    • Evaluation of:
      • Color
      • Clarity
  2. Chemical Examination of Urine
    • Specific gravity
    • Protein
    • Glucose
    • pH
    • Bilirubin
    • Urobilinogen
    • Nitrite
    • Leucocyte Esterase
    • Ketones
    • Blood
  3. Microscopic Examination of Urine
    • Cells
    • Casts
    • Crystals

CLINICAL MICROSCOPY

Changes in Unpreserved Urine
  • Physical changes:
    • Color: Darkened due to oxidation or reduction of metabolites.
    • Clarity: Decreased due to bacterial growth & precipitation of amorphous material.
    • Odor: Increased due to multiplication of bacteria or decomposition of urea to ammonia.
  • Analyte Changes (Table 2-2):
    • Color: Modified/darkened due to oxidation or reduction of metabolites.
    • Clarity: Decreased due to bacterial growth and precipitation of amorphous material.
    • Odor: Increased due to bacterial multiplication causing breakdown of urea to ammonia.
    • pH: Increased due to breakdown of urea to ammonia by urease-producing bacteria/loss of CO2CO_2.
    • Glucose: Decreased due to Glycolysis and bacterial use.
    • Ketones: Decreased due to Volatilization and bacterial metabolism.
    • Bilirubin: Decreased due to Exposure to light/photo oxidation to biliverdin.
    • Urobilinogen: Decreased due to Oxidation to urobilin.
    • Nitrite: Increased due to Multiplication of nitrate-reducing bacteria.
    • Red and white blood cells and casts: Decreased due to Disintegration in dilute alkaline urine.
    • Bacteria: Increased due to Multiplication.
    • Trichomonas: Decreased due to Loss of motility, death.

CLINICAL MICROSCOPY

Routine Urinalysis
  • Color: Detects blood, bilirubin, and other pigments.
  • Clarity: Detects presence of cellular and crystalline elements.
  • Specific gravity (SG): Measures the concentration of urine.
  • pH: Determines the acidity / alkalinity of urine.
  • Protein: Elevated levels indicate kidney disorders (proteinuria).
  • Glucose: Elevated levels indicate diabetes mellitus (glycosuria).
  • Ketones: Elevated levels indicate diabetes mellitus or starvation (ketonuria).
  • Blood: Detects red blood cells or hemoglobin (hematuria / hemoglobinuria).
  • Bilirubin: Elevated levels indicate liver disorders.
  • Urobilinogen: Elevated levels indicate liver or hemolytic disorders.
  • Nitrite: Detects bacterial infection.
  • Leukocyte esterase: Detects white blood cells / infection.
  • Microscopic (cells, casts, crystals): Determines the number and type of cellular elements.

ANATOMIC LABORATORY

  • Responsible for the analysis of the following:
    • Surgical specimens
    • Frozen sections
    • Biopsies
    • Cytological specimens
    • Autopsies

CYTOLOGY SECTION

  • Processing and examination of tissue and body fluids for the presence of abnormal cells, such as cancer cells.
  • PAP Smear (Papanicolau) - One of the most common tests performed in cytology.

HISTOLOGY SECTION

  • Processing and staining tissue obtained from biopsies, surgeries, autopsies and frozen sections.
  • Pathologist examines the tissues.

CYTOGENETICS SECTION

  • Section in which chromosome studies are performed to detect genetic disorders.
  • Specimens being analyzed include:
    • Blood
    • Amniotic fluid
    • Tissue
    • Bone marrow specimen