Intra-Rater and Inter-Rater Reliability of Pressure Pain Algometry of the Sural and Tibial Nerves in Asymptomatic Elite Youth Footballers

Comments

Authors Response

Reviewer: 1

I would like to congratulate the authors for a well structured and written manuscript.

The authors would like to thank reviewer 1 for their positive comments.            

2.2. Participants: the procedure to recruit participants is well described, but standard information on whether the participants read and signed an informed consent is not included. Also, and since the sample included U16-18 players, it should be stated if their parents or legal tutors did also authorize their participation in the study.

The authors thank reviewer 1 for their comment. The following detail has been added. ‘All participants read the participant information sheet and signed the informed consent form prior to participating in the study. Where players were under the age of 18 at the time of recruitment, their parents or legal guardians provided this authorisation.’ This appears on lines 85-89 in the resubmitted manuscript with track changes

2.2. Participants: "a convenience sample of elite youth players". Were they male, female or coed? This is clear in the rest of the manuscript, but not in the sample description.

The authors thank reviewer 1 for their comment. The following term ‘male’ has been added to page 78, line to denote this

Line 77: Table 1, with the description of the eligibility criteria is missing from the manuscript.

The authors thank reviewer 1 for their comment. Table 1 has been added and can be found in the methods section.

Line 118: Avoid starting a sentence with a numeral "30 kPa/s was chosen to give...."

The authors thank reviewer 1 for their comment. The term beginning of the sentence has been changed to ‘thirty’ as suggested. This appears on line 127 in the resubmitted manuscript with track changes

Line 123: I suggest changing "plinth" to "medical plinth" or some other synonym. When I read plinth I imediatlly recalled the structure to hold a vase or sculpture (pedestal). Indeed, this was what a quick google search retrieved, and may cause confusion on readers whose first language is not english.

The authors thank reviewer 1 for their comment. The following detail has been added. The term has been changed to ‘medical plinth’ as suggested in each reference.

Line 158: the country of origin of the SPSS software is missing from the decription. It ends with New York, and should include also "USA", in similar fashion to the way authors described the algometer in Line 113).

The authors thank reviewer 1 for their comment. This detail has been added as suggested. This appears on line 182 in the resubmitted manuscript with track changes

Line 167-168: the following sentence is odd, and appears to be incomplete or, at least, not articulated with the surrounding text: "Intraclass correlation coefficients (ICCs) with 95% confidence intervals (CI) calculated to assess intra-rater and inter-rater reliability. "

The authors thank reviewer 1 for their comment and attention to detail here. The  word ‘were’ has been added to clarify the sentence. It now reads ‘Intraclass correlation coefficients (ICCs) with 95% confidence intervals (CI) were calculated to assess intra-rater and inter-rater reliability.’ This appears on line 193 in the resubmitted manuscript with track changes

Line 169: please improve the description of the quality ranges for the ICC. Currently is "excellent 0.75>", but it would be more readable if something similiar to "excellent: >0.75" or "excellent (>0.75)".

The authors thank reviewer 1 for their comment. The description of the ICC quality ranges have been changed as suggested. This appears on lines 194-5 in the resubmitted manuscript with track changes

Line 174-176: the authors forgot to delete the template instructions.

The authors thank reviewer 1 for their comment. The template instructions have been deleted as suggested.

Line 178: please avoid starting a sentence with a numeral.

The authors thank reviewer 1 for their comment. The numerical value has been changed to Thirty-nine. This appears on line 208 in the resubmitted manuscript with track changes

3.2 Mean and range of PPT values: while the range of pressure for each nerve is described, it is not clear if this range is the result of the pooled values from each rater. It would be more interesting to find in this section a table with some descriptive statistics (mean, standard deviation, range) for each rater, and for each nerve. This would also be more transparent to the reader when analysing the statistical results.

The authors thank reviewer 1 for their comment. As suggested, an additional Table has been included (please see Table 3). This provides the mean, standard deviation and minimum and maximum PPT values for each nerve as assessed by each rater. This appears on line 219-220 in the resubmitted manuscript with track changes

Line 204: there seems to be a missing round bracket in this sequence of results. Please consider using square brackets, in addition to the round ones, when adding a second layer of parentheses.

The authors thank reviewer 1 for their comment. The additional brackets have been added and square ones have been added when using a second layer of parentheses as suggested in the surrounding section.

Table 3: the unit of SEM and MDC should be included. I believe in this case, that should be kPa.

The authors thank reviewer 1 for their comment. The detail has been added to the legend of Table 3 (now Table 4). This appears on line 249 in the resubmitted manuscript with track changes

Line 207: the authors suggest some possibilities to the lowe ICC for the inter-rater reliability being caused by algometer application differences, and points of application variations. One other hypothesis forwarded by the authors is that this may be the result of the "rate of force application". However,, in the Methods, the authors state that the rate of pressure application was constant at 30 kPa/s. Are the authors refering to force exerted by the researcher with the algometer against the skin, and not by the algometer itself? Is the algometer not able to compensate this?

The authors thank reviewer 1 for their comment and appreciate them drawing attention to this important point. The reference to rate of force application has been replaced by ‘the force exerted by each researcher with the algometer against each participants’ skin’ which the authors agree is a more accurate statement. This appears on lines 260-261 in the resubmitted manuscript with track changes

Line 207: still related to the previous comment, the authors state that the inter-rater reliabiliity may be affected by the "variation in point application". This suggestion deserves a little more discussion, since the point of application was not selected by the rater, but by the 4th researcher (non-rater). In essence, this study presents the inter-rater reliability of handeling the algometer, since the detection of the point of measurement was not performed by the raters. The reliability of this identification by the 4th researcher is another issue, but it should be recognized and discussed, perhaps in the Limitations section.

The authors thank reviewer 1 for their comment. A statement has been added to the limitations section addressing this. It reads ‘The identification of testing points in our study was made by a non-testing 4^th researcher. Although this was done to enhance the accuracy of point location across participants, the reliability of this method was not assessed. Therefore, the results only reflect the inter-rater reliability of handling of the algometer and not point location which may further limit the algometers clinical value.’ This appears on line 344-348 in the resubmitted manuscript with track changes

Line 208-210: the form in which the sentence ends after the comparison with other authors seems odd. Please re-read and correct if necessary.

The authors thank reviewer 1 for their comment. The sentences have been separated and reworded to aid clarity. They now read: ‘Our inter-rater ICC values and 95% confidence interval ranges were comparable to Fingleton et al., (2014) (0.56-0.90)[11]. However, Walsh and Hall (2009)[12] (0.85-0.96) and Sterling et al., (2000) (0.92-0.97) demonstrated higher values.’ This appears on line 261-263 in the resubmitted manuscript with track changes

Line 219: repetition on "the first dorsal first dorsal interossei".

The authors thank reviewer 1 for their comment. The repetition has been deleted.

Line 238-240: when reading this paragraph, I got the idea that the authors were comparing their results to other authors performing similiar measurement. However, the authors have previously stated that ankle nerves have not yet been tested. Only after consulting the cited references was I able to understand it was a comparison to avaialable research on other nerves. Please clarifiy in this paragraph that the comparison is with nerves from other body segments. Even the the remaining text of the paragraph (line 240-242) may not be enough for an inattentive reader.

The authors thank author 1 for their point here. The comparison with other studies assessing the ICCs of nervous tissue in other body parts has been added to the beginning of the paragraph.

This reads ‘The lower ICC values found in inter-rater compared with intra-rater reliability is consistent with other studies that have examined PPTs of the nervous tissue in other body segments [11, 15]’

This point has been reinforced mid paragraph by altering a sentence to read

‘Walsh and Hall (2009)[12] (0.85-0.96) and Sterling et al., (2000) (0.92-0.97) demonstrated higher ICC values when testing nervous tissue at the hip/knee [12] and median/radial/ulnar nerve trunks [13] respectively.’

Line 244-247: the comparison is interesting. However, the authors do not state for the readers' convenience that the Sterling sample was >18. Actually, it was a sample with three age groups, whose results were not reported by group and therefore we cannot have an idea if age indeed hinders pain sensation.

The authors thank reviewer one for their comment. This point has been clarified and now reads.

‘The study populations of Fingleton et al., (2014)[11], Walsh & Hall et al., (2009)[12] and Sterling et al., (2000)[28] were all ≥ 18 years of age. Although no study provided sufficient detail to relate specific age profiles to PPT values, adolescents have been reported to have reduced pain thresholds related to ‘growing pain’ [29]. Therefore, it is possible that our lower PPT values were also related to our study populations age.’ This appears on lines 325-329 in the resubmitted manuscript with track changes

Line 244-247: However, and more concerning, is the fact the authors state that Sterling reported ulnar and median nerves thresholds between 240-380 kPa. The article only presents results in the form of a graph (Figure 2). How did the authors obtained this values? By eye, or using some measuring software? Also, did the authors retrivied this values from the "male" of "female" data line? The females are the only going as low as 240 kPa, but this article is based on male football players.

The authors thank Reviewer 1 for their comment here and acknowledge their point. The values were based on visual inspection of the graphs in Sterling et al., (2000).

These points have been explained in further detail and now reads

Conversely, Sterling et al., [28] found comparatively higher PPT values at the nervous tissue around the elbow. Although exact values were not reported, visual inspection of graphs in Sterling et al., (2000) suggested that PPT ranges were between > 200 to approximately 400 kPa across the median, radial and ulna nerves respectively. Even while acknowledging some error from visually inspecting the graphs, these figures are substantially higher than the PPT values found in our study.

The study populations of Fingleton et al., (2014)[11], Walsh & Hall et al., (2009)[12] and Sterling et al., (2000)[28] were all ≥ 18 years of age. Although no study provided sufficient detail to relate specific age profiles to PPT values, adolescents have been reported to have reduced pain thresholds related to ‘growing pain’ [29]. Therefore, it is possible that our lower PPT values were related to our studies populations age. ‘

This appears on line 319-329 in the resubmitted manuscript with track changes

Line 247: I believe that instead "are related to our studies population" it should be "are related to our study population"

The authors thank reviewer 1 for their comment. The alterations have been made with the end to the sentence reading ‘are related to our study population’ as suggested. This appears on line 329 in the resubmitted manuscript with track changes

Institutional Review Board Statement: please review the writing, as a parentheses is missing, as is a dot at the end of the statement.

The authors thank reviewer 1 for their comment. The parentheses and full stop have been added as suggested

Informed Consent: please clarify if in addition to the participant's consent, authorization from a parent or legal guardian was obtained.

The authors thank reviewer 1 for their comment. This detail has been added to the methods section and under the informed consent heading

Data Availability Statement: please insert the appropriate statement, as the current content are the instructions from the template.

The authors thank review 1 for their comment. This detail has been added.

Acknowledgments: a dot is missing in the end of the sentence

The authors thank reviewer 1 for their comment. This has been added as suggested.

References: please carefully review the reference list and format them according to the journal style. Also, review the books references, as they are missing basic information (ref. 1, 16) 

The references have been reviewed by two authors independently against the guidance.

Reviewer 2

authors must tell about bias and proportional error between raters

The authors thank Reviewer 2 for their comment. Linear regression was included to test each Bland-Altman for proportional bias. This detail has been added to the Methods and results section and has been outlined in the discussion. This appears on lines 197-198, 229-232, and 287-289 respectively in the resubmitted manuscript with track changes                                                                      

probably the results and conclusions must be changed

The authors thank reviewer 2 for their comment.

Although it is not clear to the precise detail that the reviewer is referring to the results and conclusions have been altered in the following way:

An additional Table has been added to the results section which outlines the PPT values found by each rater. This includes detail on the mean, standard deviation, minimum and maximum values which enhance transparency. This appears on line 219-220 in the resubmitted manuscript with track changes

As previously mentioned linear regression was included in the methods and results. This appears on lines 197-198, 229-232, and 287-289 respectively in the resubmitted manuscript with track changes

Regarding the conclusions, an additional recommendation has been made of greater sample size.

This work is of interest because it aims to validate a procedure for detecting conditions favoring ankle tendon injuries.

The authors would like to thank reviewer 3 for their positive comments.            

The study was designed in a relevant way and carried out a priori with the necessary rigor.

The authors would like to thank reviewer 3 for their positive comments.

We can only regret that the ethics opinion was issued by the ethics committee of the University of Birmingham to which the authors belong and not by an independent committee. The references of the advice must be mentioned in the text as well as those of the insurance contract protecting the persons who have been the subject of the investigations.

The authors thank reviewer 3 for their comment. While the authors understand the reviewers concern, the University of Birmingham is a research-led institution with a robust ethical process. As requested, additional detail about the insurance utilised by club professionals and protecting the players has been added to the methods section. This appears on lines 71-73 in the resubmitted manuscript with track changes

Statistically, given the small size of the sample, the authors should provide proof of the "normal" nature of the population allowing the tests to be used.

The authors thank reviewer 3 for their comment. Currently no normative data exists for PPT values in this population. This point, along with the small sample size, has been acknowledged in the limitations section of the paper. This appears on lines 349-352 in the resubmitted manuscript with track changes

A further statement has been integrated with the conclusion that suggests future studies require greater sample sizes to verify these results.

This appears on lines 357-358 in the resubmitted manuscript with track changes

An anatomical drawing would be enlightening on the topographical situation of the sural, tibial and peroneal nerves, supplementing the less precise information of the photographic images presented in the article.

The authors thank reviewer 3 for their comment. An additional figure (Figure 1) has been added to outline the anatomy of the peripheral nervous  tissue at the ankle.