A Cross-Sectional Observational Study Testing Reliability and Validity for Tactile Acuity with Grid Localization in Healthy Patients

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Molly Horning, SPT, Luke Laycock, SPT, & Leslie Terwilliger, SPT

24 Comments on “A Cross-Sectional Observational Study Testing Reliability and Validity for Tactile Acuity with Grid Localization in Healthy Patients

  1. First of all, great project guys! I had a question considering gender and your study as I saw a big percentage of your population was female. Did you guys see any difference from male to female? Or do you think having more male participants would have changed your results at all? Thanks!

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    • Hi Miranda! Since 75% of our participants were female it does make you wonder if results would have been different had the ratio been more evenly split. Based solely on the grid localization testing I calculated that female mean percent correct was 77% and male mean percent correct was 82%. These numbers tell me that the grid reliability results probably would not have changed substantially. Also, I looked into inter-rater reliability and on the surface it appears males demonstrated better consistency between raters with 44% having exact same scores vs 18% of females having exact same scores between researchers. Overall these trends suggest that had our study included more males, our results may have indicated an even better inter-rater reliability for grid localization testing. However, our sample size is so small that it is hard to say for sure. More advanced statistical analysis would be needed to confirm these trends and to look into the correlation to TPD. Thanks for your question!

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  2. Hey guys! Awesome presentation. My CI for this upcoming clinical is also collecting data on grid localization on the lumbar spine for Dr. Zimney so I think that’s pretty cool! My question for you is are there other ways that tactile acuity be measured besides grid localization? Thank you!

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    • Hey Erica! That is really cool that your CI is also participating in Dr. Zimney’s research! It is a very interesting topic. There are many ways to measure tactile acuity. The ones I am most familiar with include, two-point discrimination, point to point discrimination, and graphesthesia. Two-point discrimination is the ability to discern when two nearby objects touching the skin are truly two points rather than one. Point to point discrimination assesses the precision in pointing to a location on the patient’s skin that was previously touched by the tester. Graphesthesia is assessing the accuracy of recognizing a letter that was drawn on the patient’s skin. All of these are great ways to clinically assess tactile acuity. Thanks for the question! Let me know if you have any others! 🙂

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  3. Great presentation guys! Given what you found in your study, were there any future research ideas you had that stemmed from your results that future cohorts could potentially tackle with Dr. Zimney? Thank you!

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  4. Thank you, Ashley! Right now the next step has already been taken as Dr. Zimney is currently collecting data on patients in the general public to see what their values are with the grid localization testing procedure. This is going to provide more generalizable data than what we found because a small sample size of healthy 20-30-year-old patients was our participant make-up. It seems Erica Thyen’s CI is helping collect data out in the field!

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  5. Wow, good work everybody! It is super interesting to see the development of a new assessment technique and to see researchers try to establish normative data. In regards to how the patient was familiarized with the grid, how exactly was that done? I know it said that they were given a reference grid and familiarized with the grid, but maybe more info about how that process worked may be helpful. Also, do you think that different processes of familiarizing the patient with grid localization may be beneficial or detrimental to results? Again, great job, and it’s super exciting to see new procedures be developed!

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    • Thanks Kristi for the question! To familiarize the participant with the grid, first we gave them a picture of the grid that was labeled with numbers to have in front of them during the assessment. Second, we tested, or “poked’, each quadrant in the gird while stating the corresponding number associated with it. This was done once before each assessment of grid localization. That way the patient was able to feel the stimuli corresponding with the grid along visual assistance of the labeled picture of the grid. It seems like we went to a high measure to make sure the participant would report accuracy with the grid localization, but we had decided our goal was not to trick the participant but to give them the resources to state where they think they felt the stimulus in order to truly test tactile acuity and avoid a guessing game. With the resources we had, I feel this may have been the best way to familiarize the participants with the grid. Another study by Harvie, et al. actually took a picture of each participant’s body part, this study assessed tactile acuity at the back of the neck, to set it as the background on a tablet for their localization assessment. Seeing the grid on the participants back might have helped the participant to visualize and accurately report where the stimulus was coming from. This may have been a good alternative way to help familiarize the participant but is a little more high tech than what we had available and we were aiming to use a tool that is cost effective to improve the availability of the tool to all clinics. I hope that answers everything! Thanks again!

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  6. Great presentation guys! In my current clinical rotation, we have a patient with Complex Regional Pain Syndrome whose main complaint low back pain. Looking at the reliability results that your found for inter-rater reliability, would you recommend the protocol you used for the grid localization test as a potential outcome measure for this patient? (Especially since the patient will likely be placed on multiple therapists’ schedules.)

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    • Good question, Brooke. As it sits right now, the grid localization testing has only been tested on healthy individuals in a young adult population. The next step is to test a larger variety of participants and/or patients with a certain diagnosis (CLBP, CRPS, etc.). It would be a fine measure to use in evaluations of non-healthy patients but more information is needed with this group in order to be fully backed by the current best evidence. Interestingly enough, Dr. Zimney has been collecting data on patients and the general public, so the wheels are turning to get that information! It would be interesting to assess your patient’s fluctuating CRPS presentation and how that would change their grid localization accuracy and scores. Thanks for your question!

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  7. This is a super interesting topic and I enjoyed your presentation! If you went back and asked your subjects if they have chronic low back pain do you think you would see a noticeable relationship with their tactile acuity scores? Also, I was wondering if you guys had a truly random sequence or if you had the same “random” sequence for each participant? Thanks!

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    • Hey Alyssa! As of right now the grid localization has only been tested on healthy individuals to get normative values. The next step is using the grid on patients who have low back pain or other chronic pain. My hypothesis would be that patients with chronic low back pain would have lower scores corresponding with impaired somatosensory processing or decreased tactile acuity. To answer your second question, there were 5 sets of number orders that were created with a random number generator and out of these 5 sets it was randomized what set the researcher would perform on the participant. So sometimes the participant would get the same set of numbers by both researchers and other times they wouldn’t. Hope that makes sense!

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  8. Great work everyone! It was cool to see the results of your study knowing that I participated. My question for you all is similar to Brooke’s question, what interventions would you recommend to specifically improve a patient’s score on the grid localization test if you did decide to use it as an outcome measure? Thanks!

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    • Hey Chris, good question! Like many other tests, the grid localization test can actually be the intervention. For an example, a therapist would be able to use grid localization as an intervention with a similar protocol to our study to the test but giving the patient feedback after every “poke” (correct or incorrect). The therapist could also give a longer (5 seconds) pokes. As the patient improves the therapist could give shorter (1-2 seconds) pokes. Similar to the length of the poke, the therapist could use different tools to poke the patient such as a hard object such as a unrolled pin to a soft object such as a cotton ball. This helps the brain to process the stimulus. Just a few ideas our group has talked about! Thanks!

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  9. Hey guys, great presentation! I had a few questions after watching the video and reading the poster, but it looks like they were common questions as they have already been answered! Here is a more broad question; it was mentioned that there is a weak negative correlation between two point discrimination and the grid localization indicating two different aspects of somatosensation. Did your literature review or research suggest which may be more affected in chronic pain populations?

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    • Hey Hannah, interesting question. Right now, there is not a lot of research on grid localization as this formal assessment is quite new to sensory testing. As you’ve read in the previous comments, Dr. Zimney is implementing more research on the general population! So to answer your question, research supports TPD, but that is because it is well established. It would be safe to say that if the patient’s TPD assessment is poor, then TPD as an intervention would help and if grid localization testing is poor then grid localization as an intervention would be best. I hope that answers your question, Hannah!

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  10. Great job! It was interesting to see the results of a study that I participated in. Your group did a very good job of presenting the material in a clear and concise way. In the discussion you listed many patient limiting factors. In further research, how could you prevent or minimize the influence of these limitations?

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    • Hey, thanks for the question, Morgan. With some limitations that I gave, it is tough to account for because your general population is going to have varying characteristics. It would be difficult to assess the amount of body hair, participant fatigue, epidermis thickness, and how much a participant is truthfully testing. We did find that BMI had no correlation, so that was nice to not include as a limitation to this study. We also had young (22-30 years old) participants who were primarily female (n=27/36). We would ask that the age range account for all of the adult population with a more even split in terms of gender in future studies.

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  11. Great job everyone! This was a fun study to participate in and it is exciting to see the results of this study. I think everyone did an incredible job of presenting. My question is do you think there would be any difference with a patient’s ability to successfully recognize the targeted grid based on body size? For instance, someone who is thinner would have the outer grid blocks towards the peripheral edges of a patient’s back whereas a larger individual the outer grid blocks would be more centralized on the patient’s back. This may need further testing and even different sizes of grids to target smaller or larger individuals. Once again, great presentation.

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    • Hey Ty, thanks for the question! I also noticed this while we were performing the tests and we did actually look into a correlation between BMI and accuracy of grid localization, but there was no significant correlation between the two. The threshold of the lumbar spine of two point discrimination, that has been previously developed, is 5 cm, so this is why the squares of the grid are 5 cm by 5cm. If the squares were smaller, it may be more difficult for the patient to determine what square was tested. In contrast, if the squares were bigger, it would then be too easy. Also, the provider completing the assessment could use the grid in 3 x 3 squares rather than 3×4 squares if that is more applicable to the patient. Prior to starting the testing, the original grid we had was 3×5 squares, we decided this may be too big for the majority of the participants in this study. But further down the road, it would be a good idea to have more than one size. The grid is mostly used for a reference point for the provider to keep track of the squares that were tested and to assure repeated squares tested are truly the same square or area. Hope that make sense! Thanks again!

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  12. Great presentation guys! It is interesting to hear about how new tests and measures become validated and this is a great example. My question for you is would you expect grid localization to be beneficial over other areas of the body? This may need different sized grids as well. Thanks!

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    • Hey Tyler! I think just like any other tactile discrimination tool, it would be possible and useful to use the grid localization technique over other areas of the body. As Leslie stated earlier, we decided square size based on two-point discrimination threshold for the low back. So when testing another body area we would need smaller grids not only because of a decrease in surface area, but also due to different two-point discrimination thresholds. Overall, depending where a patient is having pain, I see training tactile acuity as a good tool to have in the tool box to combat the smudging in the brain’s sensory cortex!

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  13. Hey everyone, great presentation. I really liked the distinction between the grid localization and two point discrimination. I’m curious if level of physical activity might have some influence on results in future studies. Thanks!

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    • Amy, that would definitely be something to look into! Our research included “healthy” individuals but this is skeptical as we didn’t ask questions about activity level, diet, etc. We labeled them “healthy” based on the sole criteria of absence of low back pain. Since activity level and low back pain aren’t necessarily correlated (despite what some may think), I’m not sure physical activity levels would have a major impact on grid localization scores. Of course to know for sure we would have to conduct research! Thanks!

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