Uncertainty About Evidence

By Pam Marshalla

Q: I still am uncertain about evidence in therapy. According to you, laboratory research is not the only place from which evidence comes. How can this be? I am confused. This is not what I was taught.

The originators of the term “evidence-based practice” wrote their whole book to say that health practitioners need evidence to support what they do; however, evidence could not come exclusively from laboratory research. They wrote:

“External clinical evidence [i.e., laboratory research] can inform, but can never replace, individual clinical expertise” (Sackett et al, 1997, p. 4).

Their entire book is devoted to the concept that a practicing clinician cannot rely solely upon laboratory evidence because there never is enough laboratory evidence to support what we do. We always need more than what the laboratories put out and what the journals publish.  We must rely upon our prior clinical experiences (they call this “individual clinical expertise”) as well as the needs, desires, wants, aims, goals, and preferences of the client himself (they call this “patient choice”).

When it comes down to it, very few techniques actually undergo the rigors of formal laboratory research. When we have laboratory research to back up our procedures, we use it. But when it doesn’t exist, we must rely upon our scientific and analytical minds, our intuition and creativity, our natural teaching ability, and the process of trial-and-error, to determine the best approach for each client with whom we work. That’s what the original authors said, that’s what ASHA says, and that’s what I mean when I say it.

But please don’t rely on what I say. When in doubt about a professional term, always return to the original authors.


  • ASHA/American Speech-Language-Hearing Association (2010) Evidence-Based Practice. www.asha.org
  • Sackett, D. L., & Richardson, W.S., & Rosenberg, W., & Haynes, R.B. (1997) Evidence-Based Medicine: How to Practice and Teach EBM. Edinburgh: Churchill Livingstone.
  • Sackett, D.L., Rosenberg, W.M.C., Gray, J.A.M., & Richardson, W.S. (1996) Evidence-based medicine: What it is and what it isn’t. British Medical Journal, 312, 71-72.

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