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Cytogenetics

Label Cultures

In the high-stakes environment of a clinical laboratory, the physical vessel containing the patient’s cells is the only link between the biological specimen and the diagnostic report. Labeling is not merely an administrative task; it is a fundamental patient safety control. A mix-up at the culture stage is particularly dangerous because the cells will grow and produce a perfect, analyzable karyotype that belongs to the wrong person. Therefore, rigorous labeling protocols must be enforced at the time of culture initiation

The Two-Identifier Rule (Culture Level)

Just as with the primary specimen tube, every culture vessel (flask, tube, petri dish, slide chamber) must be labeled with two unique identifiers. This ensures traceability throughout the weeks-long culture process

  • Primary Identifier: The Laboratory Accession Number (e.g., “24-1234”). This number is unique to that specific specimen event and links the physical object to the patient’s data in the Laboratory Information System (LIS)
  • Secondary Identifier: The Patient’s Name (Last, First) or Date of Birth
    • Constraint: Due to the small surface area of some culture vessels (like 15 mL tubes or 35 mm dishes), writing the full name can be difficult. The Accession Number is non-negotiable; the secondary identifier is required unless physical space makes it impossible, in which case a truncated identifier (e.g., Last Name) may be permissible per institutional policy, provided the Accession Number is prominent

Sub-Labeling: Culture Distinction

Beyond patient identity, the label must communicate the nature of the specific culture within that vessel. Since multiple cultures are set up for a single patient, the label must distinguish them to allow for troubleshooting and mosaicism analysis

  • Culture Letter/Number: (e.g., “A”, “B”, “C”). This differentiates the replicate tubes
  • Condition/Time: (e.g., “72h”, “48h”, “Unstim”, “PHA”). This prevents processing errors during harvest. For example, knowing which tube is the “24-hour” culture ensures it is harvested the next day, while the “72-hour” tube is returned to the incubator
  • Harvest Date: Writing the intended harvest date on the tube/flask (e.g., “Harv: 10/24”) acts as a visual cue to the laboratory scientist , preventing cultures from being overgrown or harvested prematurely

Labeling Durability & Placement

The culture environment is hostile to standard office supplies. Labels must withstand specific conditions

  • Ink Stability: Markers must be permanent, waterproof, and resistant to alcohol. Standard Sharpies may bleed or fade when wiped with ethanol during sterile hood work. Laboratory-grade markers (e.g., VWR, Fisherbrand) or cryo-resistant labels are required
  • Environment Resistance
    • Heat & Humidity: Incubators run at \(37^\circ\text{C}\) with \(>90\%\) humidity. Paper labels without adhesive backing will peel off. Ink can smudge
    • Water Bath: Harvest often involves dipping tubes in a \(37^\circ\text{C}\) water bath. Labels must remain legible when wet
    • Solvents: Fixative (3:1 Methanol:Acetic Acid) is a powerful organic solvent used during harvest. It will strip the ink off many labels instantly. Writing directly on the frosted area of a tube/slide is often safer than relying on a sticker
  • Placement
    • Flasks: Label the side or top, never the bottom (viewing area). Do not obscure the microscopic view of the cell monolayer
    • Petri Dishes: Always label the Base, not the Lid. Lids can be accidentally swapped during feeding or harvesting. If the ID is on the lid and the lid is moved to a neighbor’s dish, a sample mix-up occurs
    • Slides: Label the frosted end using pencil (graphite is resistant to fixative/stains) or a chemical-resistant printed label. Never use wax pencil or standard ink on slides destined for fixative

Chain of Custody (The “Setup Log”)

The physical label is supported by documentation. At the time of setup, a “Culture Worksheet” or LIS Log is created

  • Verification: The laboratory scientist records the number of vessels established (e.g., “Setup 2 flasks: A and B”). This tells the harvesting laboratory scientist exactly what to look for weeks later
  • Tech ID: The initials/ID of the person who labeled the tubes are recorded. This accountability encourages diligence and allows for error tracking if a labeling issue is discovered later