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Cytogenetics

Culture or Probe Failures

In a Cytogenetics laboratory, a failure to obtain results is considered a significant “adverse event” because it directly impacts patient care, potentially necessitating a repeat invasive procedure (like a bone marrow biopsy or amniocentesis). Documenting these failures is not merely a clerical task; it is a regulatory requirement (CLIA/CAP) and a critical component of Continuous Quality Improvement (CQI). Systematic documentation allows the laboratory to distinguish between random, unavoidable failures (due to specimen quality) and systemic operational issues (reagent or equipment failure)

Identification & Classification of Failure

The first step in documentation is accurately classifying the type and extent of the failure. This classification dictates the subsequent corrective actions

  • Culture Failure
    • No Growth/Low Mitotic Index: The cells failed to divide. This is common in patients on heavy chemotherapy or with hypocellular bone marrows
    • Contamination: Bacterial, fungal, or yeast overgrowth that destroys the human cells. This is a critical quality event
    • Incubator Failure: Mechanical failure leading to cell death (temperature/CO2 excursion)
  • Probe (FISH) Failure
    • Hybridization Failure: No signals visible
    • High Background: Excessive “noise” or non-specific binding that makes scoring impossible
    • Cross-Hybridization: The probe binds to the wrong chromosomes

The Documentation Workflow (Incident Reporting)

When a failure occurs, it must be recorded in the Laboratory Information System (LIS) and often in a separate Quality Management log

  • The Variance/Exception Report: A formal internal document must be created detailing:
    • Patient Identifiers: Name, MRN, Accession Number
    • Specimen Type: (e.g., Bone Marrow, Peripheral Blood)
    • Nature of Defect: (e.g., “Culture B contaminated with fungus on Day 3”)
    • Laboratory scientist ID: Who discovered the issue?
    • Immediate Action: (e.g., “Culture discarded,” “Attempted rescue with antibiotics,” “Re-hybridized slide”)
  • Root Cause Analysis (RCA): The documentation must include an investigation into why the failure occurred
    • Specimen Factors: Was the sample clotted, hemolyzed, too old (>48 hours), or low volume?
    • Process Factors: Was the incubator temperature out of range? Was the media expired? Did the laboratory scientist forget to add mitogen (PHA)?
    • Reagent Factors: Did a specific lot of probe fail across multiple patients?

Corrective Actions & “Rescue” Attempts

Documentation must track what was done to try to salvage the result. This proves that the laboratory made every reasonable effort to obtain a diagnosis

  • FISH Troubleshooting
    • If a FISH slide fails, the lab might attempt to “re-hyb” (wash off the probe and re-apply) or adjust the stringency (temperature/salt concentration) of the wash steps. These attempts must be logged
  • Culture Troubleshooting
    • If a culture is growing slowly, the lab might add “conditioned media” (growth factors) or extend the incubation time
  • Reflex Testing
    • If cytogenetics fails, the documentation should note if the sample was reflexed to another method, such as Chromosomal Microarray (CMA), which can work on non-dividing DNA, provided there is enough sample volume

The Final Report & Physician Notification

If the failure is total and no result can be generated, the final report must clearly communicate this to the clinician

  • “QNS” or “Test Cancelled”
    • The report typically states: “Analysis attempted but failed due to [reason, e.g., lack of dividing cells].”
    • Disclaimer: It is crucial to state that a failure to obtain results does not rule out a chromosomal abnormality
  • Physician Notification
    • For urgent cases (e.g., prenatal or acute leukemia), the physician should be notified verbally by phone before the final written report is released. This call must be documented in the LIS (Who was called, Time, Date, Read-back confirmed)
  • Request for Redraw
    • The report should explicitly state if a new specimen is required