How do you know that when you measure 1 gram of something such as NaCl, you’ll get the same amount of salt as someone else who is also weighing 1 gram of NaCl? Or that one liter of gas delivered by a metered pump into a car in Mexico City is the same one liter volume that was part of a shipment placed into an oil tanker in New Orleans?
You know because an 1875 treaty makes it so.
On the surface, it may seem like a mundane problem—ensuring that two measurements, made by different people using different instruments, are the same. But when not only commerce but lives depend on accurate measurement, such as in drug discovery and development or food safety, the problem becomes more critical and complicated.
Which is why representatives from seventeen nations got together in Paris back in 1875, and signed a treaty organizing how countries could work together to ensure measurement uniformity and concordance. This treaty—amended slightly in 1921 and expanded to presently include fifty-five member countries—not only provides assurances that measurements across borders are the same, but also ensures that measurements within a country are the same –within certain pre-defined acceptable tolerances.
The main concept at the heart of the treaty is one of connection, although it’s commonly referred to in the industry as traceability. The story begins with the one meter (or metre) platinum bar housed in Paris that defined the length of the meter. To ensure that one meter is the same everywhere, a system of certifications was put in place so that anyone doing a measurement of length could follow a chain of connections that ultimately led to the one-meter bar in Paris. It looks something like this:
This system of connection and traceability back to a single accurate measurement standard is part of what ensures measurement uniformity. These days, however, most measurements are traced back to universal physical constants (for instance the speed of light which together with the vibration frequency of an atom of Cesium 133 defines the length of a meter) rather than physical objects such as the one meter bar in Paris. The lone exception is the definition of mass, which is still traced back to a physical artifact, the “prototype” kilogram in Paris. Effective in 2018 all base quantities will be traceable to universal physical constants.
Beyond comparison to a uniform measurement standard, in the years after the treaty there was growing recognition that how you make your measurements is also critical to achieving measurement uniformity. This recognition led to the development of documentary standards which provide technical information covering the range of factors which contribute to measurement traceability
And thus, ISO, the International Standards Organization, came to be, in London in 1946. Now with members from over 163 countries, ISO produces documentary standards for many products and services. Among these are standards on how to know that you have a good system for ensuring measurement quality—including how to ensure proper training of people making measurements, as well as which type of instrument is appropriate for making the measurements.
The connection between ISO documentary standards and measurement traceability lies in what happens at each step of the traceability chain. Is each link of the chain strong and unbroken, all the way back to the national standards body (e.g., the National Institute of Standards and Technology- NIST, for those in the US)? Are the appropriate measuring instruments at each step used and calibrated correctly? (In this context any comparison between measuring instruments and measurement standards is considered a calibration, regardless of whether the instruments are actually adjusted.) If we can answer “yes”, then we have the happy situation wherein calibration, traceability and compliance with quality standards all work together to keep everyone’s measurements marching in step.
There are three ISO documentary standards that are particularly relevant to the life science industry:
This standard is becoming more and more newsworthy, so let’s review it in a little more depth. Within ISO 17025, clause 5.1.2 mentions essential factors included in the standard, directing laboratories to “take account of these factors in developing test and calibration methods and procedures, in the training and qualification of personnel and in the selection and calibration of the equipment it uses.” In other words – good laboratory practices, regardless of the particular standard or quality system, require you to consider these nine key technical elements:
These nine technical elements found in ISO 17025 are also included in some form in the various clauses of ISO 15189 and ISO 15195. This reference to table is a cross-check, showing where to find the corresponding clauses in ISO 15189 and ISO 15195.
Lina Genovesi, PhD, JD
Lina Genovesi is an engineer, scientist and attorney. In addition to maintaining her private practice as a corporate, regulatory and intellectual attorney, she is engaged in developing investigative articles, technical product reviews, regulatory and research summaries, clinical protocols, clinical regulatory submissions, and healthcare and regulatory policy analyses.
Her education encompasses a Juris Doctor from Temple University, a PhD in Chemical and Biochemical Engineering from Rutgers University and an MS in Chemistry from Oregon State University.