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Safety

Risk Assessment

In the context of the clinical laboratory, biological risk assessment is the systematic process of evaluating the risks associated with handling biological agents and toxins. It is the cornerstone of Infection Control and Biosafety. Unlike chemical safety, where hazards are often fixed and well-defined by a Safety Data Sheet (SDS), biological hazards are dynamic; the risk changes depending on the procedure being performed, the concentration of the pathogen, and the immune status of the laboratory scientist. A robust risk assessment determines the appropriate Biosafety Level (BSL), the necessary Personal Protective Equipment (PPE), and the engineering controls required to prevent Laboratory Acquired Infections (LAIs)

The Risk Assessment Framework

The risk assessment process is a qualitative and quantitative evaluation that answers three fundamental questions: What can go wrong? How likely is it to happen? What are the consequences? In the clinical laboratory, this process follows a structured path, moving from identifying the agent to evaluating the procedure and finally determining the mitigation strategies

Agent Hazard Identification (Intrinsic Properties)

The first step is understanding the enemy. The laboratory scientist must evaluate the specific characteristics of the suspected or known pathogen. While an SDS exists for chemicals, the biological equivalent is the Pathogen Safety Data Sheet (PSDS). Key factors include:

  • Pathogenicity and Virulence: Does the organism cause disease in healthy humans? How severe is the disease? (e.g., Staphylococcus epidermidis vs. Yersinia pestis)
  • Infectious Dose: How many organisms are required to cause infection? Agents with a low infectious dose (e.g., Francisella tularensis or Shigella) pose a significantly higher risk than those requiring a high dose (e.g., Salmonella)
  • Route of Transmission: How does the agent enter the body?
    • Inhalation (Aerosols): The most difficult route to control (e.g., Mycobacterium tuberculosis, Brucella spp., Neisseria meningitidis)
    • Percutaneous (Inoculation): Needlesticks or broken glass (e.g., Hepatitis B, HIV)
    • Ingestion: Hand-to-mouth contamination (e.g., Enteric pathogens)
    • Mucous Membrane Contact: Splashes to eyes or nose
  • Stability: How long can the organism survive on bench surfaces or in dried blood? Spore-formers (like C. difficile or B. anthracis) are highly persistent
  • Availability of Prophylaxis/Treatment: Is there a vaccine available (e.g., Hepatitis B)? Is the organism susceptible to standard antibiotics, or is it a Multi-Drug Resistant (MDR) organism?

Procedural Hazard Evaluation (The Activity)

The agent itself is only half the equation; what the laboratory scientist does with the agent drives the risk. A standard blood draw (venipuncture) carries a different risk profile than culturing the same blood in a bottle

  • Aerosol Generation: This is the primary hidden danger in the microbiology and hematology laboratory. Many routine procedures generate invisible respirable droplets that can remain suspended in the air. High-risk activities include:
    • Centrifuging (without safety cups)
    • Vortexing or vigorous mixing
    • Pipetting (blowing out the last drop)
    • Opening snap-top tubes or lyophilized ampoules
    • Catalase testing on an open bench (bubbling creates aerosols)
  • Concentration and Volume
    • Direct Specimen: Working with a primary patient sample (sputum, blood) usually involves a lower concentration of organisms. This is generally lower risk
    • Culture/Amplification: Once an organism is grown on a Petri dish or in a blood culture bottle, the concentration increases by orders of magnitude. A colony on a plate is pure, concentrated pathogen. Sniffing a culture plate (a forbidden practice) or working with cultures outside a Biological Safety Cabinet (BSC) drastically increases risk
  • Use of Sharps: Any procedure involving needles, scalpels, or glass slides increases the risk of percutaneous injection, bypassing the skin’s natural defense barriers

Host Factors (The Laboratory Scientist)

The risk assessment must consider the person performing the work. A pathogen that is a minor nuisance to a healthy worker can be fatal to another

  • Immune Status: Staff who are immunocompromised (due to medication, chemotherapy, or HIV), pregnant, or have underlying medical conditions are at higher risk for opportunistic infections or severe outcomes from standard pathogens (e.g., Listeria or CMV in pregnancy)
  • Vaccination Status: Personnel handling blood must be vaccinated against Hepatitis B. Personnel in specialized labs may require vaccines for Meningococcal disease, Typhoid, or Rabies
  • Competency and Training: An experienced microbiologist creates fewer aerosols and spills than a student or trainee. The level of supervision required is a factor in the risk calculation

Determination of Control Measures

Once the hazards are identified, the risk assessment dictates the control measures. This leads to the assignment of a Biosafety Level (BSL). In clinical laboratories, work is primarily divided between BSL-2 and BSL-3

Biosafety Level 2 (BSL-2)

This is the standard for most routine clinical laboratory work (Hematology, Chemistry, routine Microbiology) involving moderate-risk agents present in the community (e.g., Staph, Strep, Salmonella, HIV, Hepatitis)

  • Risk Assessment Outcome: Percutaneous injury, mucous membrane exposure, or ingestion are the primary concerns. Aerosol transmission is not the primary route, but precautions are taken
  • Controls Required
    • Access is restricted
    • Standard Microbiological Practices are followed (no eating, drinking, or mouth pipetting)
    • Engineering: Class II Biological Safety Cabinets (BSC) are used for procedures likely to create aerosols. Centrifuges have safety cups
    • PPE: Lab coats, gloves, and face protection (if splashes are anticipated)

Biosafety Level 3 (BSL-3)

Required for agents that can cause serious or lethal disease through inhalation (aerosol transmission). In a clinical setting, this applies to the Mycobacteriology (TB) suite and the manipulation of specific systemic fungi or potential bioterrorism agents (e.g., Brucella, Francisella)

  • Risk Assessment Outcome: The primary risk is breathing in the pathogen. The infectious dose is often very low
  • Controls Required
    • Containment: All work is performed strictly inside a Class II or Class III BSC. No open-bench work is permitted
    • Ventilation: Solid-wall separation from the rest of the lab, negative air pressure (air flows in, not out), and exhausted air is not recirculated (often HEPA filtered)
    • PPE: Respiratory protection (N95 or PAPR) is mandatory, along with solid-front gowns (wraparound) to prevent contact with street clothes

Trigger Events for Risk Assessment

Risk assessment is not a one-time “fill and file” document. It is a continuous cycle that must be revisited under specific circumstances:

  • New Procedures: Before validating a new test platform or bringing a new instrument online
  • New Pathogens: If the lab begins testing for a new organism (e.g., setting up testing for Ebola or a novel strain of Influenza)
  • Emerging Resistance: The identification of Multi-Drug Resistant organisms (like CRE or Candida auris) may require heightened contact precautions
  • Accidents/Near Misses: If a spill occurs or an employee is exposed, a risk assessment (Root Cause Analysis) determines why the current controls failed
  • Renovations: Construction activities can disrupt ventilation and airflow, necessitating a reassessment of containment

The “Hierarchy of Controls” in Bio-Risk

The final output of the risk assessment is the implementation of controls, prioritized by effectiveness:

  1. Elimination/Substitution: (Most Effective) Replacing a dangerous pathogen with a surrogate strain for QC purposes (e.g., using an attenuated strain of Yersinia rather than the virulent wild type)
  2. Engineering Controls: Isolating the hazard from the worker. (e.g., Biological Safety Cabinets, sealed centrifuge rotors, self-sheathing needles)
  3. Administrative Controls: Changing the way people work. (e.g., prohibiting recapping of needles, mandating Hepatitis B vaccination, restricting access to the lab)
  4. Personal Protective Equipment (PPE): (Least Effective) Gloves, gowns, masks, and eye protection. PPE is the last line of defense; if PPE is the only thing preventing infection, the risk assessment implies the process is inherently unsafe