eLetters

60 e-Letters

published between 2017 and 2020

  • Understanding NNTs

    Roe et al have written a useful article on the continuing misuse of relative risk, and the importance of understanding relative risk and absolute risk difference in injury risk outcomes in randomised controlled trials. In describing the Number Needed to Treat (NNT) they miss out an important word- the NNT is the number needed to treat to prevent one _extra_ adverse event, not to prevent a single adverse event. To see thus suppose the NNT was m. In their notation the risk in the intervention group is IG and the Control group is CG. The number of events expected in the intervention group if we treated m of them is mIG. To prevent one event we have mIG=1 and so we have to treat m=1/IG subjects to prevent one event. However we would expect mCG events in the control group. To prevent one _extra_ event in the intervention group we would require mCG-mIG =1 (assuming CG>IG) . Thus m=1/(CG-IG) which is the definition of the NNT. They could also, perhaps, have mentioned the problems in using the NNT, such as differing baselines leading to it being uninterpretable as described, for example by Stang, A., Poole, C., & Bender, R. (2010). Common problems related to the use of number needed to treat. Journal of Clinical Epidemiology, 63(8), 820–825

  • RE: Does leisure time physical activity protect against low back pain? Systematic review and meta-analysis of 36 prospective cohort studies

    Shiri et al. conducted a meta-analysis to examine the effect of leisure time physical activity on non-specific low back pain (LBP) (1). Adjusted risk ratio (RR) (95% confidence interval) of moderately/highly active individuals, moderately active individuals and highly active individuals against individuals without regular physical activity for frequent/chronic LBP was 0.89 (0.82 to 0.97), 0.86 (0.79 to 0.94) and 0.84 (0.75 to 0.93), respectively. For LBP in the past 1-12 months, adjusted RR did not reach the level of significance in any levels of physical activity. The authors concluded that leisure time physical activity might reduce the risk of chronic LBP by 11%-16%. I have some concerns about their study by presenting negative information regarding protection of LBP by physical activity.

    First, Saragiotto et al. conducted a meta-analysis on the effectiveness of motor control exercise (MCE) in patients with nonspecific LBP (2). MCE focuses on the activation of the deep trunk muscles and targets the restoration of control and coordination of these muscles. They concluded that MCE was probably more effective than a minimal intervention for reducing pain, but did not have an important effect on disability, in patients with chronic LBP. In addition, there was no clear difference between MCE and other forms of exercises or manual therapy for acute and chronic LBP. Although there is no definite information to recommend MCE for non-specific LBP, further studies are need...

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  • International Olympic Committee consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020 (including STROBE Extension for Sport Injury and Illness Surveillance (STROBE-SIIS))

    Allow me to make use of the opportunity to extend my appreciation to the BJSM for being a publication of high standing, bringing cutting edge information to the sports medical fraternity.
    Thank you for the consensus statement of the International Olympic Committee describing the methods for recording and reporting of epidemiological data on injury and illness in sport 2020 (including STROBE Extension for Sport Injury and Illness Surveillance (STROBE-SIIS))”.[1] I found it both informative and useful.
    I have a comment about the use of the word “Nervous” in the first column of Table 5. It is an adjective whereas the rest of the words in the column are nouns that more accurately describe the tissue type under discussion. It is possibly only a linguistic error, but I am of the opinion that it should be “Nerve” or “Neural tissue”.

    Reference
    1. Bahr R, Clarsen B, Derman W, et al. International Olympic Committee consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020 (including STROBE Extension for Sport Injury and Illness Surveillance (STROBE-SIIS)). Br J Sports Med Published Online First: 18 February 2020. doi: 10.1136/bjsports-2019-101969

  • Response to “International Olympic Committee consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020 (including STROBE Extension for Sport Injury and Illness Surveillance (STROBE-SIIS))

    We read with interest the recent International Olympic Committee consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020 (including STROBE Extension for Sport Injury and Illness Surveillance (STROBE-SIIS))”.[1] While helping to clarify aspects associated with recording and reporting epidemiological data, based on the definitions included in the statement, we believe that some of the examples in Table 10 require clarification with regards to the recording of injuries and calculation of time loss.

    Consider the example for ‘Delayed’ time loss: Sunday injury, thigh contusion, able to train on Monday and Tuesday but unable to train on Wednesday and returns on Sunday (time loss starts on Wednesday even though the injury was on Sunday). Time loss (days) 3. Given the recommended reported time loss of 3-days, and definition provided whereby “time-loss days should be counted from the day after the onset that the athlete is unable to participate”, we assume Wednesday is considered as the day of onset (day 0), with subsequent impact on Thursday, Friday and Saturday resulting in a 3-day time-loss (days). When considering this example, we were then somewhat confused by the example for, ‘Intermittent’ time loss: boy with Osgood-Schlatter disease that gets reported at the start of a training camp on Monday. The player may train fully on Monday, Tuesday and Thursday, but miss training on Wednesday and Friday (time loss co...

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  • Comment on "Three steps to changing the narrative about knee osteoarthritis: a call to action."

    Whilst its principal message is clear, I wish to draw attention to three problems arising from the editorial authored by Caneiro et al.:

    1. They say, “… pain is described as an altered state of a person’s knee health influenced by biopsychosocial factors, of which many can be modified.”

    How is “knee health” different from “whole person health”?

    Just how many biopsychosocial factors can be modified?

    2. Contemporary evidence is said to support the proposition that “knee health” is “influenced by the interaction of different biopsychosocial factors” that have the property of “modulating inflammatory processes and tissue sensitivity”.

    Is there any evidence that such an interaction actually takes place?

    And furthermore, what are the postulated mechanisms for such interaction?

    3. Their Infographic (“What should you know about knee osteoarthritis?”) contains the statement “rest and avoidance makes pain worse.” Presumably they are referring to avoidance of graded exercise. But even so, how do the authors justify their conclusion that avoidance of exercise or rest "per se" can “make pain worse”?

  • ASDMAC and DFSNZ support the call for TUE Committee peer review process

    The Australian Sports Drug Medical Advisory Committee (ASDMAC) and Drug Free Sport New Zealand (DFSNZ) Therapeutic Use Exemption (TUE) committees welcome the recent discussion paper by our esteemed colleague Dr Ken Fitch entitled "Therapeutic Use Exemptions (TUEs) are essential in sport: but there is room for improvement." As the national bodies responsible for TUE assessment and processing in our respective nations, ASDMAC and DFSNZ agree that the integrity of the TUE process is sound and essential, but could be improved through a peer review process.

    Although the World Anti-Doping Agency (WADA) does screen TUEs entered in Anti-Doping Administration and Managements System (ADAMS), the supplementary screening of TUE Committees themselves, including the members, their TUE processes and procedures, as suggested by Dr Fitch would improve the reliability and standardisation of TUEs. In 2018 and 2019, ASDMAC and DFSNZ with the support of the World Anti-Doping Agency (WADA) TUE expert group designed and conducted a TUE Peer Review Audit. This process included the documentation of the proposed audit process, followed by the respective visits of each Chair to the others TUEC meeting. During the visits the Chairs assessed a number of TUE applications and outcomes to ensure that those granted were done so in accordance with the WADA ISTUE and that the WADA Medical Information to Support TUEC decisions had been appropriately interpreted. These visits also includ...

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  • Departmental Infographic Needed!

    As part of this excellent summary editorial, you mentioned how important it is to tailor your education to the needs and preferences of the patient. Therapists also have these diverse needs so it would be an excellent resource to have this in a graphical format that could be displayed openly in any department, whether it be in Outpatients or in physiotherapy for example as a visual reminder to clinicians but also visible for patients to interrogate so that they can have an understanding of what is to be expected in their consultation and by creating these expectations, will help to drive forward better, more holistic assessment and care of patients.

  • Concerns About As-Treated Analysis

    Dear Dr. McGuine et al,

    I'd like to commend you on running a large RCT on such an important topic (assessing the purported effectiveness of concussion-reduction technologies). Unfortunately I have some concerns about some aspects of your data and analysis, particularly the as-treated analysis in Table 4and your reported adherence numbers. I am hoping you can clarify these concerns and re-do parts of your analysis.

    1. In the as-treated analysis you have a very strange result. Your multivariate risk ratio (which is actually a rate ratio) is 0.63 for everyone overall, 0.64 for females, and 0.93 for males. The result for everyone should be between the results for males and females. Can you please clarify how you got these results, including the exact model(s) you used and how you calculated the rate ratios? Did you use a group*sex interaction term to get the sex-specific results?

    2. How you defined the as-treated group is concerning. You state that you only re-classified a subject if they spent >50% of their time in their non-assigned group OR if they were concussed while in their non-assigned group. This approach will bias the results of your as-treated analysis as you are deliberately misclassifying the AEs of people who do not get hurt and the non-concussed AEs of those who do. You need to classify every AE, rather than each athlete, as headgear or no headgear and repeat the as-treated analysis. Otherwise this analysis is highly questionable and...

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  • Response to the comments for the paper: Does soccer headgear reduce the incidence of sport-related concussion? A cluster, randomised controlled trial of adolescent athletes.

    To: The British Journal Sports Medicine

    We are grateful for Dr. Binney’s interest in our study and his consideration of a portion of the results presented in the manuscript.

    Listed below are our responses to each of the concerns raised in the letter.

    1. In the as-treated analysis you have a very strange result. Your multivariate risk ratio (which is actually a rate ratio) is 0.63 for everyone overall, 0.64 for females, and 0.93 for males. The result for everyone should be between the results for males and females. Can you please clarify how you got these results, including the exact model(s) you used and how you calculated the rate ratios? Did you use a group*sex interaction term to get the sex-specific results?

    Response: We thank you for noticing the mathematical inconsistency in Table 4 rate ratio results for the as-treated analyses. You are correct that if these results were from one model, the overall rate ratio estimate would need to be in-between the male/female estimates. We should note that these were actually 3 separate mixed-effects models: (1) the overall model adjusting for all variables including sex, (2) female sub-group model adjusting for all variables –excluding sex, and (3) male sub-group model adjusting for all variables –excluding sex. We apologize that the footnote in the table is unclear in this regard. We did attempt to use interaction models for this analyses, but did not achieve consistent convergence. As such, we opt...

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  • Continued Question About As-Treated Analysis

    Dear Drs. McGuine, Hetzel, and Kliethermes,

    Thank you for your thorough response to my initial comment.

    I am wondering if you could help me understand the new AE-level as-treated analysis you have done in response to Point 2. This accounts for all non-compliant AEs among all athletes, correct? If I understood you correctly, there were somewhat more than the 711 non-compliant AEs reported in the paper and which you reported in your response to Point 4, correct?

    What would be very helpful to see is a.) the number of AEs and b.) the number of SRCs that occurred during those AEs for each of the following groups when considering any non-compliant AE, not just ones from athletes who suffered an SRC while non-compliant or were non-compliant >50% of the time:

    Assigned HG/Did Not Wear:
    Assigned HG/Did Wear:
    Assigned No HG/Did Not Wear:
    Assigned No HG/Did Wear:

    Thank you again for your thorough response.

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