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Microbiology

Collection & Transport

This section covers the key steps involved in ensuring that specimens collected for microbiological analysis are handled properly before they even reach the bench for testing. These preanalytic steps are vital for generating accurate and reliable lab results, which directly impact patient care

The Big Picture: Why Preanalytics Matter

  • Garbage In, Garbage Out (GIGO): No matter how sophisticated our lab equipment, if the specimen is collected or transported improperly, the results will be unreliable
  • Patient Safety: Accurate results are the foundation of correct diagnoses and treatment plans. Errors in specimen handling can lead to misdiagnosis, delayed treatment, and potentially harmful outcomes
  • Cost-Effectiveness: Repeat collections, unnecessary testing, and prolonged hospital stays all add to healthcare costs. Proper preanalytic procedures help minimize these costs
  • Legal and Ethical Considerations: Labs are responsible for providing reliable results. Errors in specimen handling can have legal and ethical repercussions

Patient Identification and Specimen Labeling: The Foundation of Accuracy

  • Goal: To unequivocally link the specimen to the correct patient
  • Key Principles
    • Active Patient Participation: Involve the patient in the identification process whenever possible (ask them to state their full name and date of birth)
    • Two-Factor Identification: Use at least two unique patient identifiers (full name, date of birth, medical record number)
    • Verification: Compare patient information with the test request form and resolve any discrepancies before proceeding
    • Labeling at Bedside: Label the specimen container immediately after collection and in the presence of the patient
  • Essential Label Information
    • Patient’s Full Name
    • Patient’s Unique Identifier (Medical Record Number)
    • Date and Time of Collection
    • Collector’s Initials
    • Specimen Source (e.g., wound site, urine - clean catch)
  • Common Errors & Solutions
    • Misidentification: Asking “Are you Mr. Smith?” instead of asking the patient to state their name
    • Pre-labeling: Labeling tubes before collection
    • Illegible Handwriting: Use pre-printed labels or write clearly
    • Incomplete Labeling: Use a checklist to ensure all information is included
    • Lid Labeling: Place the label on the container, not the lid

Specimen Collection: The Art and Science

  • Goal: To obtain a representative sample of the infected site while minimizing contamination
  • Key Principles
    • Sterile Technique: Use sterile equipment and supplies, practice meticulous hand hygiene, and avoid contaminating the specimen
    • Appropriate Collection Device: Select the correct swab, container, or aspiration needle for the specimen type
    • Target the Infection: Collect from the site most likely to be infected (e.g., base of a wound, purulent portion of sputum)
    • Minimize Contamination: Clean the area before collection and avoid touching surrounding surfaces
    • Adequate Volume: Collect a sufficient amount of specimen for testing
  • Collection from Sites with Normal Flora
    • Challenge: Differentiating pathogens from normal flora
    • Specimen-Specific Considerations
      • Stool: Collect stool directly into a clean container
      • Wound: Aspirate material from deep within the wound (after cleaning)
      • Sputum: Collect a deep cough specimen (not saliva)
      • Throat: Swab the posterior pharynx and tonsils (avoid the tongue)
  • Blood Culture Collection
    • Key Principles: Sterile technique is paramount
    • Procedure Highlights: Meticulous skin antisepsis, correct blood volume, proper inoculation of bottles

Specimen Transport Systems and Conditions: Getting It to the Lab in Good Shape

  • Goal: To maintain the viability and integrity of microorganisms during transport
  • Three Key Factors
    • Transport Devices
      • Sterile and leak-proof
      • Contain appropriate transport medium
      • Clearly labeled
      • Examples: Amies swabs, Cary-Blair medium for stool, Viral Transport Medium (VTM)
    • Atmosphere
      • Different organisms have different atmospheric requirements (aerobic, anaerobic, microaerophilic, capnophilic)
      • Use appropriate transport systems to maintain the correct atmosphere (anaerobic transport vials, gas-generating packets)
    • Time and Temperature
      • Minimize transport time
      • Store and transport specimens at the recommended temperature range (refrigerated, room temperature, frozen, body temperature)
      • Follow lab guidelines
  • Specific Recommendations
    • Neisseria gonorrhoeae: Transport at room temperature or body temperature within 6 hours
    • Viral specimens: Transport refrigerated within 48 hours
    • Blood cultures: Transport at body temperature or room temperature; do not refrigerate

Key Takeaways

  • Preanalytic procedures are vital for accurate and reliable microbiology results
  • Patient identification and specimen labeling are the foundation of accuracy
  • Specimen collection requires careful technique to obtain a representative sample while minimizing contamination
  • Proper transport systems and conditions are essential for maintaining the viability and integrity of microorganisms
  • Continuous training, monitoring, and documentation are crucial for ensuring quality