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Fit for Purpose: Using the Right Method to Answer Scientific Questions

By Pam Jensen, Ph.D.
Senior Research Scientist, Monsanto

Analytical methods are used to measure things with adequate accuracy and precision to make conclusions. Some methods can be simple and others more complex, but they all need to be reliable.

Analytical methods are developed with a purpose in mind. They are designed to answer a specific scientific question. Analytical methods define the type of equipment needed and the steps that must take place in order to determine the desired information. No method is perfect or universally applicable; they all have limits. Part of developing the method is identifying these limits and then defining the scope within which that method should be applied. Once developed, it is important to demonstrate the method can meet the intended purpose. Scientists use method validation as a way to ensure the method can consistently deliver accurate results when used as intended. In other words, method validation shows the method is “fit for purpose.”

What does “fit for purpose” mean? It means the method is appropriate and accurate to use to answer that specific scientific question. Rigorous testing has demonstrated that the method is “fit” to accurately and reproducibly deliver the results intended for its “purpose” when used within the limits defined by the method. If a method is not validated for a particular purpose, it is unknown if the data generated will be accurate.

The concept of “fit for purpose” also applies to the decision to use a method to generate data. When deciding to use a method, it is important to understand how that method was intended to be used. A scientist must understand what the purpose is, as well as the limitations of a method. For instance, would you use an oral thermometer to test the temperature of your Thanksgiving turkey? No, because the temperature range of a thermometer intended for use by people wouldn’t cover the high temperatures reached in an oven. I also doubt you would trust the results from a home pregnancy test if you took it using your saliva, since we know these tests were developed and tested only for use with urine. These may seem like obvious examples, but the same goes for analytical methods. A good scientist will ensure they are using the right method for the right purpose. Is the method being used for the type of samples it was validated to analyze? Does the validated range cover what is being measured? It is the scientist’s responsibility to ensure that the method they are using to generate data, to answer a specific question, has been demonstrated to be fit for that purpose. Generation of unreliable data can result in “false positives” and “false negatives,” causing people to draw incorrect conclusions which can have far reaching implications.

I recently was presented with this challenge when I was approached about measuring glyphosate in breast milk. I had many methods at my disposal to measure glyphosate, but not one of them had been validated for use in breast milk. That left me with what I felt was the only option for a good scientist, to develop and validate a method myself that was fit for this purpose. So I developed and validated a method that had the sensitivity and selectivity that was needed to produce reliable results using breast milk and at the levels that might occur, had this method validated by a third party lab, and published the results in a peer-reviewed journal. As scientists it is our responsibility when addressing the scientific question at hand to ensure we are producing accurate and reproducible results by choosing methods that have been demonstrated to be fit for purpose.

Meanwhile, there has been some coverage in the media and in online forums regarding claims that another analytical method, known as the ELISA method, has detected glyphosate in breast milk samples. Again, the key question that must be asked is whether the ELISA method is “fit for purpose” when it comes to breast milk. And the answer to that question is “no.”

In fact, many of the claims that are appearing these days, about traces of glyphosate in breast milk, beer, wine and urine, are all based on ELISA results. It’s important to note that the ELISA has not been validated on any of these substances.

When you need to measure something, or evaluate when someone else measured something, it is important that you consider “fit for purpose.” Otherwise, your conclusions may not be so accurate. Glyphosate is just a case in point.

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