Lab Procedures and Testing Overview

Chapter 14: Special Collections and Procedures

Overview of Special Procedures

  • Focus on specific laboratory testing procedures, particularly those relevant to diabetes testing and therapeutic drug monitoring.
Therapeutic Drug Monitoring
  • Important for preventing toxicity in patients receiving medications.
  • Key concepts include:
      - Peak Levels:
        - Drawn 30 minutes to 1 hour after medication administration, measuring the highest concentration of the drug in the blood.
      - Trough Levels:
        - Drawn right before the next dose to ensure that the drug does not reach toxic levels.
Diabetes Testing Overview
  • Discussion of types of diabetes:
      - Type 1 Diabetes:
        - Lack of insulin production or ineffective insulin function.
      - Type 2 Diabetes:
        - Insulin resistance; insulin is present but impaired.
      - Gestational Diabetes:
        - Occurs during pregnancy, related to fluctuating hormone levels.
      - Diabetes from Other Causes:
        - Various factors leading to diabetes not classified as Type 1 or Type 2.

Key Tests

  • A1C Testing:
      - Measures glycated hemoglobin; reflects average blood glucose levels for the previous 120 days.
      - Drawn using lavender top tubes (chemistry).
      - Allows assessment of long-term glucose control.

  • Fasting Glucose Testing:
      - Patients must fast for at least 8 hours before testing to determine baseline glucose levels.

  • Oral Glucose Tolerance Test (OGTT):
      - Measures the body's ability to metabolize glucose.
      - Involves administering a glucose solution and measuring blood glucose at intervals (1 hour, 2 hours, and in some cases longer).
        - Typical glucose doses range between 200 mg to 500 mg.

  • Random Glucose Testing:
      - Can be done at any time of the day; used for quick assessments.

Important Test Procedures

  • Fasting:
      - Essential for tests assessing lipids, glucose, and others to ensure baseline measurements are accurate.

  • Urinalysis:
      - Provides a snapshot of metabolic status; non-invasive method widely used.
      - Types of collections:
        - Random Specimen: Anytime sample.
        - First Morning Specimen: More concentrated, ideal for hormone testing (e.g., pregnancy tests).
        - Timed Collections:
          - 20-hour urinary collections for creatinine clearance assessment.
        - Midstream Clean Catch:
          - Method to minimize contamination, specifically for urine cultures.
          - Requires proper cleaning of the genital area to prevent bacteria from affecting results.

Chapter 15: Special Tests

Urinalysis and Stool Specimens

Urinalysis Procedures
  • Random Specimen: To check for basic abnormalities.
  • First-Morning Urine: Concentrated affects hormone levels which may be detected (e.g., hCG for pregnancy).
  • 24-hour Creatinine Clearance:
      - The patient voids the first urine, then collects all urine for 24 hours to assess kidney function.
  • Midstream Clean Catch:
      - Patients clean the area, urinate briefly into toilet then collect midstream urine to minimize contamination.
Stool Sample Procedures
  • Stool Culture:
      - Used to grow bacteria from a stool sample.
  • Ova and Parasite Testing:
      - Identifies eggs (ova) and parasites in stool.
  • C. Diff Testing:
      - Diagnoses Clostridium difficile infections, typically from antibiotic use.
  • Occult Blood Testing:
      - Detects hidden blood in stool, used to check for gastrointestinal bleeding.
Sample Collection Considerations
  • Pediatric Specimen Collection:
      - Pediatric urine collection bags are used due to difficulty in instructing young children.
  • Catheterized Specimens:
      - Collected directly from the bladder, allows for contamination-free cultures.
  • Suprapubic Aspiration:
      - Invasive method for collecting urine directly from the bladder, used when necessary to ensure sterile collection.

Important Terms and Techniques

  • Chain of Custody:
      - Legal documentation of the handling of specimens for forensic purposes.
  • Blood Cultures:
      - Two sets (anaerobic and aerobic) usually collected to diagnose infections; careful site preparation required.

Practical Evaluations and Final Exams

  • Upcoming Exam Structure:
      - Matching questions on tests and departments.
  • Demonstration of Skills:
      - Review of different techniques, such as venipuncture and urinalysis dipstick tests.
Important Dates
  • Quiz: Tomorrow
  • Exam 3: This Friday
  • Practical: Next Thursday
  • Open Book Assignment: Due by May 6

Review and Study Strategies

  • Cumulative Exam: Covers all material, utilizing resources from previous exams and open book reviews.
  • Target weak points in study materials for focused review.
Conclusion
  • As the semester concludes with these chapters, focus on practical procedures and testing protocols. Prepare for assessments through active review and practice of required skills, ensuring a thorough understanding of concepts and applications discussed.

*These comprehensive notes cover key aspects from Chapters 14 and 15 pertaining to laboratory procedures, testing protocols, and relevant considerations crucial for effective clinical practice in the healthcare setting.