June 12, 2019Mari Ishak Gabra, MS
A major concern for clinical laboratory employees is exposure to biological agents during sample collection, contact with patients, or during laboratory analysis. Minimizing exposure begins with the implementation of an exposure control plan (ECP), a mandated written document that 1) identifies sources of exposure, 2) communicates information to employees, 3) provides methods of compliance, and 4) records training/vaccinations/incidents. An ECP will also follow OSHA’s bloodborne pathogens (BBP, 29 CFR1910.10030) and PPE (29 CFR1910 Subpart 1) standards that require protection for workers who handle human blood or other potentially infectious materials (OPIMs), and the Cal/OSHA standard for airborne transmissible pathogens (Title 8, Section 5199). These standards are further discussed in this article.
Bloodborne pathogens and OPIMs
Bloodborne pathogens are infectious agents in blood samples that can transmit disease in humans. Clinical laboratory workers can be exposed to blood through needlestick/sharps injuries, and mucous membrane and skin exposures. The Centers for Disease Control and Prevention (CDC) identifies the following pathogens of primary concern:
Human immunodeficiency virus (HIV), which weakens the human immune system by attacking T cells. This impairs the body’s ability to fight off other infections and disease.
Viral hepatitis, which leads to the inflammation of the liver. The most common types of hepatitis viruses transmitted through blood or bodily fluids are hepatitis B (HBV) and hepatitis C (HCV). Vaccination against HBV is required for all health care workers. While there is no vaccine for HCV, new treatments are available.
OPIMs, which are carried by other bodily fluids that are analyzed in clinical laboratories including, but not limited, urine, fecal, saliva, and cerebrospinal fluid. For example, the CDC has identified potential sources of Ebola virus transmission through urine and saliva samples, and studies have shown that urine samples from individuals with Zika can contain high concentrations of infectious virus.
Precautions against bloodborne pathogens and OPIMs
OSHA recommends following universal and standard precautions in addition to following the training and guidelines in the BBP standard:
Universal precautions help to identify infectious agents in human samples through testing to implement necessary handling precautions and eliminate exposure.
Standard precautions include hand hygiene (washing hands after removing gloves) and use of appropriate PPE—such as lab coats, gloves, face mask and face shield—that does not permit infectious materials to pass through to employee’s clothes, skin, or mucous membranes during sample handling. PPE should always be removed when leaving the lab work area.
Other precautions include the use of appropriate disinfectants (e.g., 10 percent bleach solution) to clean surfaces before and after sample handling to eliminate accidental exposure. Contaminated lab coats or laundry should be transported in fluid-resistant containers/bags.
Airborne transmissible pathogens
Airborne or aerosol transmissible diseases (ATDs) can be transmitted by either inhaling particles/droplets or direct contact of particles/droplets and mucous membranes in the respiratory tract or eyes. The California/OSHA ATD standard lists several pathogens and aerosol generating procedures that are specific to clinical laboratory work. Here are some of the common ATDs:
Brucellosis can be transmitted by infectious aerosols or occupations exposures through infected samples when performing gram staining or blood tube inoculations. A case was reported in 2006, when a clinical laboratory worker contracted an infection when performing blood culture isolate on an open laboratory bench.
Tuberculosis (TB) can be transmitted in clinical laboratories that are part of health care facilities with patients that might have diagnosed or unsuspected TB disease. Testing or evaluating samples for patients with TB disease can also pose a risk.
Laboratory aerosol generating procedures include vigorous pipetting, mixing, centrifugation, inoculating cultures, vortexing, and homogenizing samples with ATD pathogens.
Precautions against ATDs
OSHA lists additional transmission-based precautions (TBP) to augment standard precautions, in order to interrupt any route of transmission that may not be completely interrupted using standard precautions alone. TBPs include:
Engineering controls and PPE that remove, reduce, or isolate infectious aerosols, such as the use of biosafety cabinets with HEPA filters and proper ventilation in the workspace. Some workers might be required to wear respirators, face shields, or masks depending on the suspected ATD.
Work practices that are required by all laboratory workers handling infectious samples. Workers must disinfect all surfaces before and after work using 10 percent bleach solution. Autoclaving of all tools and glassware on a daily basis is also recommended. Periodic examination and updated vaccinations should be offered by the employer.