Frequently Asked Questions

Interlaboratory testing can, among other things, be used to validate a test method or measurement technique, generate precision statements, investigate causes of systematic error, and assess lab performance through comparison with other labs’ results. Interlaboratory testing holds several advantages over internal and round robin testing, including increased efficiency, wider scopes and less biased results, and the option to use environmentally sensitive or destroyable samples.

CTS’ approach stems from our shared history with the National Institute of Standards and Technology (NIST), formerly known as the National Bureau of Standards (NBS). We go beyond a simple pass/fail analysis to provide a three-level evaluation of performance on individual samples, simultaneous analysis of the results of samples for consistency, and comparison to other labs in the industry. We accomplish this through a multivariate analysis, and we present the data to customers using trend charts, Comparative Performance Values (CPVs) and graphs, and data flags and comments.

CTS testing helps labs meet accreditation requirements for several bodies and provides additional organizational benefits to participants. Our testing allows for labs to evaluate both instrument calibration and operator technique and increase their reputations as reliable suppliers, and our reports provide data that can be used to diagnose inconsistencies, predict future trends, and act on potential issues. Additionally, because participants’ results are compared to other participants’, the accuracy of a lab’s performance is determined by others in the industry.

In keeping with the principles of quality assurance, we use a prepaid subscription model with consistent testing intervals to ensure that proficiency testing is a streamlined and simple process for our participants. Once a subscription is purchased, each cycle of testing in the subscription includes a shipment of samples, a data entry window for participants to submit their results on our full-service customer portal, and individualized reports that provide test-takers with detailed insight into their lab’s performance. 

For more information about enrollment, see our Subscription Terms and Policies. For more details on individual tests, visit our industry and forensic test listings. 

CTS is ANAB-accredited to ISO/IEC 17043:2023. You may view our scope of accreditation here.

We are also recognized by several organizations including A2LA, ASCLD/LAB (which is now merged with ANAB), NVLAP, NADCAP, the United Kingdom Accreditation Service, and the Standards Council of Canada; however, we encourage participants to reach out to their accrediting bodies to determine which CTS tests meet their specific accreditation or registration requirements.