Collection and recording of biological specimens in a biochemistry lab

Arvind Kumar

The collection and recording of biological specimens in a biochemistry lab require meticulous attention to detail to ensure accurate and reliable results. Proper techniques, thorough documentation, and adherence to ethical standards are essential to maintaining the integrity of the specimens and ensuring the validity of biochemical analyses.

Types of Biological Specimens

Understanding the specific types of specimens is essential for selecting appropriate collection and handling methods.

  • Blood Samples:
    • Plasma: Contains clotting factors and is used in various assays, including hormone levels, electrolytes, and coagulation studies.
    • Serum: Obtained after blood clotting; used for biochemical tests, antibody detection, and metabolic panels.
  • Urine Samples:
    • Random Urine: Collected at any time; useful for routine screening.
    • Midstream Urine: Collected after cleaning the genital area; reduces contamination.
    • 24-hour Urine: Collected over a full day; useful for comprehensive analysis of kidney function and metabolism.
  • Tissue Samples:
    • Obtained from biopsies or surgical procedures; used for histological examination and biochemical assays.
  • Saliva Samples:
    • Used for hormone testing (like cortisol), enzymes, and microbiome studies.
  • Other Fluids:
    • Cerebrospinal Fluid (CSF): Collected via lumbar puncture; used for diagnosing infections, haemorrhages, and neurological disorders.
    • Synovial Fluid: Obtained from joint spaces; analyzed for conditions like arthritis.

Collection Procedures

  1. Preparation for Collection

  • PPE: Always wear gloves, masks, and lab coats. Eye protection may be necessary, especially when collecting CSF or other fluids.
  • Sterile Equipment: Ensure all collection materials (needles, tubes, containers) are sterile and specific to the specimen type.
  • Patient Preparation: Instruct patients on necessary preparations, such as fasting for blood tests or dietary restrictions for urine collection.

  1. Collection Techniques

1. Blood Collection:

    • Types of Tubes:
      • EDTA Tubes: For complete blood counts and blood smears.
      • Serum Separator Tubes (SST): For serum assays, contain a gel that separates serum from cells.
      • Citrate Tubes: For coagulation studies.
  1. Urine Collection:
    • Types of Samples:
      • Midstream Collection: Provides a cleaner sample by reducing contamination.
    • Procedure:
      • Instruct the patient to clean the genital area with provided wipes.
      • Collect the midstream portion directly into the sterile container without touching the inside.
      • Label the container immediately after collection with the patient’s details.
  1. Tissue Collection:
    • Procedure:
      • Ensure the use of sterile instruments (scalpel, forceps).
      • Collect the tissue sample aseptically and place it in the appropriate fixative (like formalin) or preservation medium immediately.
      • Label the sample with site, date, and other relevant details.
  1. Saliva Collection:
    • Procedure:
      • Advise the patient to avoid eating, drinking, or smoking for 30 minutes prior to collection.
      • Collect saliva in a sterile container by having the patient spit or drool into the container.
  1. Cerebrospinal Fluid (CSF) Collection:
    • Materials: Sterile lumbar puncture kit.
    • Procedure:
      • Position the patient correctly and identify the lumbar puncture site.
      • Clean the area thoroughly and use sterile technique to insert the needle.
      • Collect CSF into sterile tubes; label each tube as per the collection order (e.g., for chemistry and microbiology).

Recording Procedures

  1. Labelling Samples

  • Use waterproof, smudge-proof labels or write directly on the container with indelible ink.
  • Essential information includes:
    • Patient name and ID number
    • Date and time of collection
    • Type of specimen
    • Collector’s initials and any relevant clinical information.

  1. Documentation

  • Sample Collection Log: Maintain a digital or physical logbook with entries that include:
    • Specimen type
    • Collection method (including specific techniques)
    • Collection site (for tissues)
    • Collector’s name and signature
    • Patient history (e.g., medications, symptoms)
    • Any observations made during collection (e.g., unusual appearance).

Storage and Transport

  1. Storage Conditions:

    • Blood Samples: Store at room temperature for immediate tests; refrigerate or freeze based on the analysis requirements.
    • Urine Samples: Typically refrigerated; should be analyzed within 24 hours to avoid degradation.
    • Tissue Samples: Store in formalin for histological analysis; freeze if specific biochemical assays are planned.
    • Saliva Samples: Refrigerate until analysis.

  2. Transport:

    • Use insulated containers to maintain temperature (e.g., ice packs for temperature-sensitive specimens).
    • Ensure specimens are securely packed to prevent breakage or contamination during transport.
    • Follow institutional guidelines for the transport of potentially infectious materials.

Separation Process

Plasma Separation:

  1. Immediate Processing:
    • After blood collection in a tube with an anticoagulant, gently invert the tube 5-10 times to mix the blood with the anticoagulant.
  2. Centrifugation:
    • Place the tube in a centrifuge and spin at appropriate speeds (usually 1500-3000 RPM) for 10-15 minutes, depending on the protocol.
    • Centrifugation causes the blood cells to settle at the bottom, while the plasma remains as the upper layer.
  3. Separation:
    • Carefully remove the tube from the centrifuge.
    • Using a pipette, extract the plasma layer without disturbing the cellular layer.
    • Transfer the plasma into a new sterile container and label it appropriately.

Serum Separation:

  1. Clotting:
    • After blood collection in a serum tube, allow the sample to sit at room temperature for 30 minutes to 1 hour to facilitate clotting.
    • This step is crucial for obtaining clear serum.
  2. Centrifugation:
    • Similar to plasma separation, centrifuge the clotting blood at 1500-3000 RPM for 10-15 minutes.
    • The clot will form a solid mass at the bottom, with serum above.
  3. Separation:
    • Carefully pipette the serum from the top layer without disturbing the clot.
    • Transfer the serum into a sterile container and label it appropriately.

Preservation and Disposal of Biological Samples

  1. General Principles of Preservation

  • Minimize Degradation: Use techniques that slow or prevent biochemical reactions, microbial growth, and chemical breakdown.
  • Temperature Control: Adjust temperatures to inhibit enzyme activity and microbial growth.

  1. Methods of Preservation

  1. Refrigeration:
    • Temperature Range: Typically between 2°C and 8°C.
    • Use Cases: Suitable for urine, plasma, serum, and certain tissue samples for short-term storage (up to 24 hours).
    • Considerations: Ensure samples are in tightly sealed containers to prevent contamination and evaporation.
  2. Freezing:
    • Temperature Range: -20°C for long-term storage; -80°C for more sensitive samples.
    • Use Cases: Blood, plasma, serum, and certain biological tissues. Freezing preserves DNA, RNA, and proteins.
    • Considerations: Cryoprotectants (e.g., glycerol, DMSO) are used for cell suspensions to prevent ice crystal formation.
  3. Lyophilization (Freeze-Drying):
    • Process: Removal of water under low temperature and pressure.
    • Use Cases: Long-term storage of samples like bacterial cultures, enzymes, and some types of biological drugs.
    • Considerations: Requires specialized equipment and prior stabilization of samples.
  4. Chemical Preservation:
    • Use of Preservatives: Chemicals such as formaldehyde, ethanol, or glutaraldehyde can be used for tissue samples.
    • Use Cases: Histological samples and biological specimens for microscopy.
    • Considerations: Ensure compliance with safety regulations when using hazardous chemicals.
  5. Storage in Transport Media:
    • Types of Media: Specialized media (e.g., Amie’s medium, Stuart’s medium) for microbiological samples.
    • Use Cases: Maintain viability of microorganisms during transport to the lab.
    • Considerations: Use appropriate media based on the type of microorganism being transported.

  1. General Principles of Disposal

  • Safety Compliance: Follow local and national regulations regarding hazardous waste disposal.
  • Risk Assessment: Assess the biohazard risk of samples before disposal.

  1. Methods of Disposal

  1. Incineration:
    • Description: High-temperature destruction of biological waste.
    • Use Cases: Suitable for contaminated samples, used needles, and other sharps.
    • Considerations: Requires specialized facilities and compliance with emissions regulations.
  2. Autoclaving:
    • Description: Sterilization through steam under pressure.
    • Use Cases: Effective for glassware, culture media, and non-sharp biological waste.
    • Considerations: Ensure appropriate cycles (temperature and time) for effective sterilization.
  3. Chemical Disinfection:
    • Chemicals Used: Sodium hypochlorite (bleach), formalin, or other approved disinfectants.
    • Use Cases: Surface disinfection and treatment of liquid biological waste.
    • Considerations: Follow manufacturer instructions for dilution and contact time to ensure effectiveness.
  4. Biohazard Waste Containers:
    • Description: Use clearly labelled, puncture-proof containers for sharps and other biohazardous waste.
    • Use Cases: Ensure safe collection and disposal of used needles, glass, and other hazardous materials.
    • Considerations: Never overfill containers; follow disposal guidelines for biohazard waste.
  5. Landfill Disposal:
    • Conditions: Non-hazardous, non-contaminated materials can be disposed of in regular waste.
    • Use Cases: Laboratory supplies and packaging that are not biohazardous.
    • Considerations: Ensure compliance with local waste management regulations.

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