Frequently Asked Questions

• What does receiving documentation of proficiency mean?
    The Environmental Legionella Isolation Techniques Evaluation Program issues documentation of proficiency to laboratories that have demonstrated the ability to isolate Legionella from simulated environmental samples by culture. Successfully passing the proficiency test does not guarantee that a laboratory will be able to isolate Legionella from every sample where it is present.

• How do I enroll in the program?
    Interested laboratories can pay an annual fee and enroll in the program through the Wisconsin State Laboratory of Hygiene (WSLH). Any laboratory that cultures Legionella from environmental samples is encouraged to enroll.

• We have multiple laboratories in our organization. Does each lab need to enroll separately?
    Yes. Laboratories, not organizations, receive documentation of proficiency. Each location within an organization that tests environmental samples for Legionella should create its own account and participate individually.

• How do I access my laboratory’s proficiency results?

• What is in a test panel?
    A test panel consists of 6 lyophilized samples. Participating labs rehydrate and dilute the lyophilized samples in their laboratories to create test samples. Labs then process the test samples according to their own in-house protocols. The lyophilized format allows the sample to remain stable during transport and to be used for a variety of testing protocols. Each panel contains:
    • 1-2 positives, which contain either pure Legionella or Legionella in a high ratio to contaminating organisms
    • 2 negatives, which contain no viable Legionella but may contain other non-pathogenic organisms
    • 2-3 variables, which contain low concentrations of Legionella or Legionella strains with atypical morphologies or are heavily mixed with heterotrophic bacteria

• How are results scored?
    Laboratories must submit whether or not they isolated Legionella from each test sample. To receive a passing score, laboratories must correctly identify the positive and negative samples. Two passing scores per 12 months are necessary to maintain documentation of proficiency.

• My laboratory only tests for Legionella pneumophila. Can we participate?
    Laboratories that are capable of isolating all members of the genus but can only type a subset would qualify for the program. However, laboratories that use a test method that only detects a subset of the genus would not qualify for the program.

• May I use PCR or some other non-traditional method?
    No. Laboratories must use a traditional spread-plate culture method/protocol on test panels and report these results.

• How often will we receive panels?
    WSLH distributes test panels 2 times per year. Contact or 800-462-5261 for shipping schedules, results entry deadlines, and other administrative questions.

• What happens if we fail?
    A limited number of interim panels are available to make up failures. Contact or 800-462-5261 to schedule an interim panel. Two failures in 12 months may result in revocation of the proficiency documentation and removal from the program’s member list.

• What is the value to using a lab that has documentation of proficiency from the Environmental Legionella Isolation Techniques Evaluation Program?
    Documentation from passing a proficiency testing program is one consideration for selecting a laboratory to conduct environmental testing as part of an investigation into cases of disease. Other considerations include:
    • Is the laboratory accredited by a national program for environmental testing?
    • Does the laboratory routinely perform culture for Legionella?
    • What level of identification (species/serogroup) can the laboratory perform?
    • Is the laboratory willing to save samples and isolates and share them with public health laboratories if requested during an outbreak investigation?

• What does it mean if the lab I am using does not have documentation from a proficiency testing program?
    It depends on the reason for testing environmental samples for the presence of Legionella. If you need samples tested during an investigation into cases of disease, you should consider using a laboratory that has documentation from a proficiency testing program like the Environmental Legionella Isolation Techniques Evaluation Program. However, when testing is used to validate a water management program in the absence of disease, different performance criteria may apply. Regardless of the reasons for testing, assays should be conducted by a laboratory that is accredited by a regional, national, or international accrediting body. Also, the test method used for finding Legionella should be included in that laboratory’s scope of accreditation.

• Can program members provide Legionella water management programs and remediation services?
    Although some groups will provide water management consultation and other services in addition to water testing, these services are beyond the scope of the Environmental Legionella Isolation Techniques Evaluation Program. This program only assesses laboratories in their ability to isolate culturable Legionella from water samples. This program does not assess the ability to manage building water systems or eliminate Legionella from them. Testing for Legionella may be part of a site-specific, comprehensive building water system management program. See CDC’s Practical Guide to Implementing Industry Standards for more details.

• Why does CDC offer the Environmental Legionella Isolation Techniques Evaluation Program?
    Investigating cases and outbreaks of Legionnaires’ disease often requires comparing Legionella isolates grown from patient samples to Legionella from environmental (water) samples. However, finding Legionella among the many different microorganisms present in the environment can be difficult. Also, whoever is testing the samples may use different procedures for collection, transport, and storage of samples and isolates, which could affect the chances of finding Legionella in a sample. CDC created the Environmental Legionella Isolation Techniques Evaluation Program in order to identify laboratories that demonstrate proficiency in isolating Legionella from environmental samples. These laboratories can be helpful during public health investigations. As a service to the general public and public health partners, CDC maintains a publicly accessible Member’s List.

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Page last reviewed: 6/23/2022