Sample Collection Techniques in Laboratory

Sample Collection and Handling

• Sample collection is vital for accurate lab results. Improper collection can lead to inaccurate results, costly errors and safety risks.
• Sample collection involves obtaining a specimen from a person, animal, environment, or substance for analysis.

Types of Laboratory Samples

• Clinical Samples: Blood (venous, arterial, capillary), urine, sputum, tissue biopsies, saliva, feces.
• Environmental Samples: Air, water, soil, food, surfaces (for contamination or quality testing).
• Microbiological Samples: Swabs, cultures, stool, sputum, blood cultures.

Sample Collection Techniques

• Blood Collection:
  • Venous: From veins using needles or vacutainer tubes (e.g., antecubital fossa).
  • Capillary: From fingers or heel sticks (e.g., glucose tests, pediatric blood tests).
  • Arterial: From arteries for blood gas analysis (e.g., radial artery).
• Urine Collection:
  • Midstream: Avoids contamination from urethra.
  • 24-Hour Urine: Measures kidney function/protein excretion.
  • Catheterized Urine: For patients unable to provide samples independently.
• Sputum Collection:
  • Induced Sputum: For respiratory infections (e.g., tuberculosis), deep coughing.
  • Natural Coughing: Natural method for collecting sputum.
• Tissue Biopsy:
  • Needle Biopsy: Small tissue samples (e.g., tumors, lymph nodes).
  • Surgical Excision: Larger tissue samples.

Proper Labeling and Documentation

• Label samples with patient information (name, age, sex, medical record number), sample details (type, collection date/time, test required), and collection method.
• Use tracking sheets to ensure traceability and avoid mix-ups.

Preventing Contamination

• Aseptic Techniques: Use sterile containers and equipment.
• Personal Protective Equipment (PPE): Gloves, lab coats, face shields (as necessary).
• Sterile Swabs: For microbiological samples.

Temperature Control and Sample Preservation

• Refrigeration: Keep some samples (e.g., blood, urine) at 4°C to slow microbial growth.

• Freezing: Preserve plasma/serum samples for long-term storage.

• Room Temperature: Some samples (e.g., coagulation tests) need immediate processing at room temperature.

• Preservation: Use preservatives (e.g., formalin) for preservation of biological samples, and chemical preservatives.

Sample Transport and Handling

• Use secure containers (e.g., biohazard bags for infectious samples, leak-proof containers for fluids).
• Maintain temperature control during transport with insulated coolers, ice packs, or thermostatic containers for temperature-sensitive samples.

Special Handling

• Infectious Samples: Use biohazard symbols and proper packaging for transport.
• Radioactive Materials: Use specialized containers with shielding.

Sample Preparation

• Blood Samples: Centrifugation to separate serum/plasma from blood cells; aliquoting for different tests.
• Microbiological Samples: Cultures and smears to grow bacteria/viruses and prepare microscopic slides (e.g., Gram staining).
• Tissue Samples: Fixation and embedding in paraffin followed by sectioning for histopathology.

Common Challenges in Sample Handling

• Contamination: Proper sterilization and PPE (personal protective equipment) are crucial.
• Degradation: Improper storage or transport can degrade sensitive samples (e.g., blood, DNA).
• Volume Limitations: Small sample sizes may require multiple aliquots or pooling for testing.

Time Constraints and Best Practices

• Time Constraints: Some tests need immediate processing, requiring rapid transport.
• Best Practices:
• Before collection, properly prepare materials & lab personnel with appropriate PPE (personal protective equipment).
• During collection, observe aseptic techniques, label immediately, and document all details.
• After collection, carefully handle the samples, ensuring correct storage and transport conditions.
• During transport, prioritize temperature control.