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PHYS THER
Vol. 88, No. 4, April 2008, p. 536
DOI: 10.2522/ptj.2008.88.4.536.1
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Letters and Responses

On "Intertester reliability and validity of motion assessments..." Landel et al. Phys Ther. 2008;88:43–49.


The validity of a test or measure is the extent to which that test or measure actually assesses what it is intended to assess. The research design for investigating the validity of a test or measure requires that all subjects undergo both the clinical test or measure as well as a reference standard assessment that reflects, as closely as possible, the true state of what the clinical test or measure being studied is intended to assess. The key word in both of these statements is "intend." In order for the research design to have internal validity, it is crucial that there is a match between intent of the clinical test or measure and what the reference standard can measure. No match—the research design is faulty and the result is meaningless.

In this study by Landel et al,1 the clinical test under investigation is the postero-anterior intervertebral motion test (PAIVM). So far so good. What is the PAIVM test intended to measure? Recent research informs us that clinicians use it primarily to assess pain response, but in terms of biomechanical parameters, clinicians primarily assess quality of resistance (stiffness, greater or lesser resistance to therapist-applied pressure), quantity of sagittal translation, and quality of the path of vertebral motion.2

The reference standard chosen in the present study is not appropriate because it measures quantity of intervertebral sagittal rotation. Clinicians do not intend to assess quantity of sagittal rotation with the PAIVM test. Barely 2% of the members of 2 national manual therapy organizations who responded to our "intent of assessment" survey ranked quantity of rotation as an important assessment using the PAIVM test.2 Of all the biomechanical parameters measurable, rotation was reported by clinicians as the one that they had the least intention of assessing.2 The reference standard chosen by the researchers is not a match to the intent of the clinical test. No match—the research design is faulty and the result is meaningless.

What biomechanical parameters should the researchers have used as the reference standard? According to the clinicians who use these assessments, they intend to assess stiffness, translation, and the path of the vertebrae during motion2; therefore, I suggest that the researchers should include both force and displacement to measure stiffness, and that they should measure sagittal translation and the finite center of rotation.

J Haxby Abbott

JH Abbott, PhD, MScPT, DipGrad, FNZCP, is Senior Research Fellow, University of Otago


  Footnotes
 
This letter was posted as a Rapid Response on February 11, 2008, at www.ptjournal.org.

Referenes

  1. Landel R, Kulig K, Fredericson M, et al. Intertester reliability and validity of motion assessments during lumbar spine accessory motion testing. Phys Ther. 2008;88:43–49.[Abstract/Free Full Text]
  2. Abbott JH, Flynn TW, Fritz JM, et al. Manual physical assessment of spinal segmental motion: intent and validity. Man Ther. doi:10.1016/j.math.2007.09.011.

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This Article
Right arrow Extract Freely available
Right arrow Full Text (PDF)
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when Rapid Responses are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Abbott, J H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Abbott, J H.
Related Collections
Right arrow Injuries and Conditions: Spine
Right arrow Tests and Measurements
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
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