Selecting the right analytical testing laboratory affects the quality of your data, the defensibility of your compliance records, and ultimately the safety of your products or environment. The laboratory you choose becomes a critical extension of your quality assurance program, and asking the right questions before you commit can save you time, money, and costly mistakes.

Here are the essential questions to ask when evaluating an analytical testing lab.

1. Is the Lab Accredited, and for Which Methods?

This is the single most important question you can ask, and it should be the first one. Accreditation is the formal recognition by an independent body that a laboratory is technically competent to perform specific tests. The gold standard for analytical testing laboratories is ISO/IEC 17025 accreditation, which is recognized internationally and required by many regulatory agencies.

Accreditation vs. Certification

It is important to understand the difference between accreditation and certification. Accreditation (such as ISO 17025) evaluates the technical competence of the laboratory, including its methods, equipment, and personnel qualifications. Certification (such as ISO 9001) evaluates management systems but does not assess technical competence for specific tests. A certified lab may have good processes on paper, but accreditation confirms that the lab can produce reliable results for the methods listed on its scope.

How to Verify a Lab’s Accreditation Scope

Ask for the lab’s accreditation certificate and its scope of accreditation. The scope lists every test method the lab has been approved to perform. A lab may be accredited for drinking water microbiology but not for soil chemistry. Make sure the methods you need fall within the lab’s accredited scope. You can verify accreditation status through the accrediting body’s website. Review the accreditations page of any lab you are evaluating.

State-Specific Licensing

In addition to ISO 17025 accreditation, many states require laboratories to hold specific state certifications or licenses for certain types of testing, particularly drinking water and environmental compliance testing. Ask whether the lab holds the state-level approvals relevant to your project. Using a lab without the proper state credentials can render your results inadmissible for regulatory reporting.

What It Means for Your Results

When you use an accredited laboratory, you can be confident that the results have been produced using validated methods, calibrated instruments, qualified analysts, and robust quality control procedures. Accredited results carry weight with regulators, auditors, courts, and clients. Unaccredited results may be questioned or rejected entirely.

2. What Are the Lab’s Turnaround Times and Expedite Options?

Turnaround time directly affects your project timelines, compliance deadlines, and operational decisions. Understanding how a lab defines and delivers on its turnaround commitments is essential.

Standard, Rush, and Emergency Turnaround

Most analytical laboratories offer tiered turnaround options:

• Standard turnaround: Typically 5 to 10 business days, depending on the complexity of the analysis.
• Rush turnaround: Usually 2 to 3 business days, often available for a surcharge.
• Emergency or same-day turnaround: Available at some labs for critical situations, typically at a premium fee.

At AATLS, standard turnaround is 3 to 5 business days for most analyses, which is faster than the industry average. Rush and priority options are available for time-sensitive projects.

How Turnaround Is Measured

An important clarification: turnaround time is measured from the date and time the laboratory receives your sample, not from the date you collect it. Shipping delays, incomplete chain-of-custody documentation, or samples that arrive outside of acceptable temperature ranges can all add time before the clock starts. Ask the lab how they handle these situations and what you can do to avoid delays.

Questions to Ask About Capacity

A lab that promises fast turnaround but is chronically over capacity will miss deadlines. Ask about the lab’s current workload, whether they have seasonal bottlenecks, and what percentage of results are delivered on time. A transparent lab will share this information readily.

When Faster Results Are Worth the Premium

In situations involving environmental spills, product recalls, real estate transactions, or regulatory deadlines, the cost of a rush fee is negligible compared to the cost of delayed information. Establish the lab’s expedite capabilities before you need them so you are not scrambling during a crisis.

3. How Does the Lab Handle Quality Control and Data Validation?

The reliability of your analytical results depends entirely on the rigor of the laboratory’s quality control (QC) program. A reputable lab will be transparent about its QC practices and willing to explain them in detail.

Method Blanks, Duplicates, and Spikes

Every analytical batch should include several types of quality control samples:

• Method blanks: Clean samples processed through the entire analytical procedure to verify that no contamination has been introduced by the lab.
• Laboratory duplicates: A sample analyzed twice to assess the precision and reproducibility of the method.
• Matrix spikes and matrix spike duplicates: Known quantities of target analytes added to a sample to measure accuracy and the effect of the sample matrix on recovery.
• Laboratory control samples: Standards of known concentration analyzed to verify that the method is performing within acceptable limits.

Ask the lab what QC samples are included in each batch and what their acceptance criteria are. If a lab cannot clearly articulate its QC protocols, that is a significant red flag.

Proficiency Testing Participation

Accredited laboratories participate in proficiency testing (PT) programs, analyzing blind samples provided by an external organization with results compared against known values and other laboratories. Ask whether the lab participates in PT studies for the methods you need and what their track record looks like.

Data Review and Validation

Before results leave the laboratory, they should undergo a multi-level review process. At a minimum, this includes review by the analyst, a senior analyst or supervisor, and a quality assurance officer. Ask about the lab’s data validation procedures and whether results are reviewed against QC acceptance criteria before they are reported to clients.

How QC Failures Are Handled

QC failures happen in every laboratory. What matters is how they are handled. A quality-focused lab will flag QC failures, investigate root causes, re-analyze affected samples when possible, and document the entire process. Ask the lab what happens when a QC sample fails acceptance criteria and how that affects your reported results. Transparency about QC failures is a hallmark of a trustworthy laboratory.

4. What Support Does the Lab Provide Beyond the Report?

An analytical report is only as valuable as your ability to understand and act on the results. The best laboratory partners go beyond delivering numbers and provide the context and support you need to make informed decisions.

Help Interpreting Results

Analytical data often requires interpretation in the context of regulatory standards, historical trends, or project-specific objectives. Does the lab offer consultation to help you understand what your results mean? Can they explain detection limits, compare your data against relevant regulatory thresholds, and help you identify trends or anomalies? A lab that delivers a report and disappears is providing a commodity. A lab that helps you understand and use your data is providing a service. Explore our full range of testing services to see how comprehensive support is built into our process.

Regulatory Compliance Guidance

Regulations change, and keeping up with evolving requirements for water quality, environmental monitoring, food safety, or workplace safety can be a full-time job. Ask whether the lab can provide guidance on which tests are required for your specific regulatory context, what standards apply, and how often you need to test. A knowledgeable lab can help you avoid both under-testing (which creates compliance risk) and over-testing (which wastes money).

Sampling Training and Support

Improper sampling is one of the most common sources of unreliable analytical data. Ask whether the lab provides sampling guidance, training for your field personnel, or pre-assembled sampling kits with the correct containers, preservatives, and instructions. These services can dramatically improve data quality from the very first step.

Chain of Custody and Legal Defensibility

For projects involving litigation, regulatory enforcement, or insurance claims, chain of custody (COC) documentation is as important as the results themselves. Ask the lab about their COC procedures and whether their documentation meets the standards required for legal proceedings.

Ongoing Partnership vs. Transactional Relationship

The best laboratory relationships are partnerships, not transactions. A lab that understands your business and regulatory environment can proactively identify issues and help you stay ahead of compliance requirements. Look for a lab that assigns a dedicated point of contact and treats your needs as a priority regardless of account size.

Why AATLS

AATLS is an ISO/IEC 17025 accredited, CDC ELITE certified analytical laboratory based in Tucson, Arizona. We are veteran-owned and committed to providing not just accurate results, but the guidance and support our clients need to act on those results with confidence. Our team is accessible, responsive, and genuinely invested in the success of every client we serve. Learn more about us and our commitment to quality and service.