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Letters to the Editor to:

Scientific Articles:
Dianne Bryant, Paul Stratford, Robert Marx, Stephen Walter, and Gordon Guyatt
Patients Can Provide a Valid Assessment of Quality of Life, Functional Status, and General Health on the Day They Undergo Knee Surgery
J Bone Joint Surg Am 2008; 90: 264-270 [Abstract] [Full text] [PDF]
*Letters to the Editor: Submit a response to this article

Electronic letters published:

[Read Letter to the Editor] An Additional Thought
Dorothea Z. Lack, Ph.D.   (23 April 2008)
[Read Letter to the Editor] Dr. Bryant et al. respond to Dr. Lack
Dianne M Bryant, Paul Stratford, Robert Marx, Stephen Walter, and Gordon Guyatt   (11 March 2008)
[Read Letter to the Editor] Confounding factors in the valid assessment of patients undergoing knee surgery
Benedict A Rogers, Meghana Dhamdhere, Nick J Little   (11 March 2008)
[Read Letter to the Editor] Demand Characteristics Affect Response
Dorothea Z. Lack, Ph.D.   (6 February 2008)

An Additional Thought 23 April 2008
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Dorothea Z. Lack, Ph.D.,
Psychologist
California Pacific Medical Center

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Re: An Additional Thought

dlack7{at}aol.com Dorothea Z. Lack, Ph.D.

To The Editor:

In their response to my original Letter to the Editor, Bryant et al. have supported their results with the following: "As always, empirical evidence trumps theoretical considerations. We demonstrate through three separately tested hypotheses that measures obtained on the day of surgery are similar to measures obtained 4 weeks preoperatively in this population. So, as it turns out, theoretical concerns have proved groundless for this particular population(1)."

I just reread the letter named above. Now that some time has passed, I realize that previous psychological research would predict that scores on the day of surgery should show increased anxiety over measures obtained 4 weeks earlier(2). Anxiety is transient and ebbs and flows, the curve for anxiety usually increases as the subject moves closer to the stressor. Therefore, if the results were valid, one would expect them to be higher on the day of surgery, not the same as they were 4 weeks earlier.

The author did not receive any outside funding or grants in support of her research for or preparation of this work. Neither she nor a member of her immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of her immediate family, is affiliated or associated.

References:

1. Bryant D, Stratford P, Marx R, Walter S, Guyatt G. Patients can provide a valid assessment of quality of life, functional status, and general health on the day they undergo knee surgery. J Bone Joint Surg Am. 2008;90:264-270. [Letter to The Editor] J Bone Joint Surg Am. epub 6 Feb 2008. http://www.ejbjs.org/cgi/eletters/90/2/264.

2. "Motivation and Emotion in Sport" Kerr, J.H. Psychology Press, 1997 UK
Dr. Bryant et al. respond to Dr. Lack 11 March 2008
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Dianne M Bryant,
Assistant Professor
University of Western Ontario,
Paul Stratford, Robert Marx, Stephen Walter, and Gordon Guyatt

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Re: Dr. Bryant et al. respond to Dr. Lack

dianne.bryant{at}uwo.ca Dianne M Bryant, et al.

Dr. Lack(1) and Professor Lingard(2) are both quite right that there is good reason to think that patients’ assessment of their status obtained on the day of surgery may be distorted by contextual factors. Indeed, it was concern about such effects that motivated our study(3). At the same time, it is possible that patients can, despite the stresses of the day, report their status accurately.

As always, empirical evidence trumps theoretical considerations. We demonstrate through three separately tested hypotheses that measures obtained on the day of surgery are similar to measures obtained 4 weeks preoperatively in this population. So, as it turns out, theoretical concerns have proved groundless for this particular population.

It is still possible that there is a small subpopulation – the very anxious, for instance – to whom our results do not apply. To test this interesting hypothesis that Professor Lingard has suggested, we repeated all analyses on the quartile of our population with the greatest emotional dysfunction on the SF-36 mental health domain on the day of surgery. The results in this population proved essentially the same as that for other patients. Thus, we find no evidence of a sub-population to whom our overall results do not apply.

In her commentary, Lingard(2) expresses concern over our decision to report the KOOS score as an overall aggregate score. As it turns out, the statement we provided to defend the decision proved open to misinterpretation. We stated that “each domain yielded similar results, and thus, for ease of reporting, we computed an overall aggregate score only…”. By this statement, we did not mean that the scores on each domain were similar but rather that the results of the analyses for each domain were similar and that given that this study already reports the results of 5 questionnaires, that to report similar results in all domains of each questionnaire might be unnecessarily burdensome to the reader. In fact, the mean score and standard deviation was 56.3±18.5 for the symptom domain, 59.0±19.0 for the pain domain, 68.9±18.9 for the function domain, 35.7±23.9 for the sport and recreation domain and 29.8±18.0 for the quality of life domain. These results are consistent with those reported in previous studies.

Dr. Lack(1) and Professor Lingard(2) are correct that although these results may apply to other populations, we will be not be confident until direct testing in these other populations takes place. Further experiments addressing the issue of day-of-surgery ratings will, therefore, be most welcome.

References:

1. Bryant D, Stratford P, Marx R, Walter S, Guyatt G. Patients can provide a valid assessment of quality of life, functional status, and general health on the day they undergo knee surgery. J Bone Joint Surg Am. 2008;90:264-270. [Letter to The Editor] J Bone Joint Surg Am. epub 6 Feb 2008. http://www.ejbjs.org/cgi/eletters/90/2/264.

2. Lingard EA. Commentary and perspective on: Patients can provide a valid assessment of quality of life, functional status, and general health on the day they undergo knee surgery (2008;90:264-70). 2008 Feb. http://www.ejbjs.org/Comments/2008/cp_feb08_lingard.dtl. Accessed 2/2/08.

3. Bryant D, Stratford P, Marx R, Walter S, Guyatt G. Patients can provide a valid assessment of quality of life, functional status, and general health on the day they undergo knee surgery. J Bone Joint Surg Am. 2008;90:264-270.
Confounding factors in the valid assessment of patients undergoing knee surgery 11 March 2008
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Benedict A Rogers,
Specialist Registrar
St Peter's Hospital, Chertsey, UK,
Meghana Dhamdhere, Nick J Little

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Re: Confounding factors in the valid assessment of patients undergoing knee surgery

benedictrogers{at}hotmail.com Benedict A Rogers, et al.

To The Editor:

We read with interest the paper by Bryant et al.(1) and would like to make the following points.

1. The title states the study considers knee surgery. We feel it should be made explicitly clear, both in the title and conclusion, that the results and inferences made relate to Anterior Cruciate Ligament (ACL) reconstruction and arthroscopic knee surgery. Further, the fact that arthroscopic surgery can either be diagnostic or therapeutic (i.e. meniscal resection) is not clarified. This study may not be valid for trauma or arthroplasty knee surgery.

2. Several possible confounding factors have not been considered and, thus, the methodology remains open to the criticism of selection bias.

a. Table I reports that 42% of patients had previous knee surgery, but no analysis of this subgroup was carried out in the subsequent results?

b. Other than smoking, how many any of the patients have significant co-morbidities, either knee or non-knee related?

c. Are the results reliable for all ages? The demographics of the entire study cohort are detailed in Table I – being predominantly young males - but no subset analysis has been performed. Since ACL reconstruction and arthroscopic surgery is frequently performed on a relatively young patient cohort it may be difficult to analyse for an age correlation.

d. Body Mass Index (BMI) and obesity – that relate to body image(2) – has not been considered. The mean and standard deviation of both height and weight is given for the entire patient cohort, but does the hypothesis of the study remain valid for both high and low BMI patients?

e. The socio-economic class of patients study has not been evaluated. High socio-economic patients are generally better educated which can significantly impact on the subjective scoring of quality of life, function and general health(3,4). A subset analysis assessing whether different socio-economic class affects the hypothesis of this study would be informative.

f. Physiotherapy and exercise are commonly employed as an initial non -surgical treatment for knee pathology and a key aspect of which is patient education(5-7). Have any patients had any physiotherapy?

g. Points e & f above allude to the patients knowledge of knee surgery/function and, thus, may alter the scores.

3. In results section, it states that day-of-surgery results predict the scores from four weeks prior to surgery. This statistical analysis is temporally retrograde. Does the same hold true for temporally anterograde analysis, namely do the scores from four weeks prior to surgery predict day-of-surgery scores? Whilst linear regression is one statistical method available for this, the paper does not elaborate on the “assumptions of linear regression” have been made of these scores?

4. The results state that the “reliability of the SF-36 MCS was moderate”. Could any for the factors outlined above account for this poor reliability?

5. What evidence or reference exists for either the day of surgery or four weeks prior being seen as the “Gold Standard?”

6. Oxford Knee Score(8) (OKS) & American Knee Society score(5) (AKS) are two commonly used validated knee scoring systems. Is there any specific reason for selecting the 5 scoring systems used and excluding the OKS and AKS?

The study’s conclusion may hold true for a specific patient cohort, but care needs to be used if it is to be extrapolated to the general population of patients undergoing knee surgery

The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

References:

1. Bryant, Stratford P, Marx R, Walter S, Guyatt G. Patients can provide a valid assessment of quality of life, functional status, and general health on the day they undergo knee surgery. J.Bone Joint Surg.Am 2008; 90:264-270.

2. Friedman, Reichmann SK, Costanzo PR, Musante GJ. Body image partially mediates the relationship between obesity and psychological distress. Obes.Res. 2002; 10:33-41.

3. Steenland, Halperin W, Hu S, Walker JT. Deaths due to injuries among employed adults: the effects of socioeconomic class. Epidemiology 2003; 14:74-79.

4. Hawker, Wright JG, Glazier RH, Coyte PC, Harvey B, Williams JI, Badley EM. The effect of education and income on need and willingness to undergo total joint arthroplasty. Arthritis Rheum. 2002; 46:3331-3339.

5. Insall, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res. 1989;13-14.

6. Keays, Bullock-Saxton JE, Newcombe P, Bullock MI. The effectiveness of a pre-operative home-based physiotherapy programme for chronic anterior cruciate ligament deficiency. Physiother.Res.Int. 2006; 11:204-218.

7. Rooks, Huang J, Bierbaum BE, Bolus SA, Rubano J, Connolly CE, Alpert S, Iversen MD, Katz JN. Effect of preoperative exercise on measures of functional status in men and women undergoing total hip and knee arthroplasty. Arthritis Rheum. 2006; 55:700-708.

8. Dawson, Fitzpatrick R, Carr A, Murray D. Questionnaire on the perceptions of patients about total hip replacement. J.Bone Joint Surg.Br. 1996; 78:185-190.
Demand Characteristics Affect Response 6 February 2008
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Dorothea Z. Lack, Ph.D.,
Psychologist
Independent Practice, Affiliate Staff, California Pacific Medical Center

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Re: Demand Characteristics Affect Response

dlack7{at}aol.com Dorothea Z. Lack, Ph.D.

To The Editor:

As a psychologist, it seems likely to me that the demand characteristics of the situation on the day of surgery would overwhelm a patient's judgment about quality of life, functional status and general health. Demand characteristics include concern about the surgeon's opinion, wanting to please the surgeon, wanting to be seen as a "good" patient. Factors like these have been demonstrated to influence responses and were first reported by Rosenthal et al. as early as 1976(1).

Additionally, I agree with the Commentary & Perspective by Elizabeth A. Lingard, BPhty, MPhil, MPH(2). There is wide variance in the degree of anxiety experienced by patients on the occasion of surgery. These differences should be measured and reported for the sake of accuracy. The use of partial tests affects the validity of these measures and cannot be considered reliable.

Furthermore, a patient's perception of arthroscopy and arthroplasty are not comparable. Arthroplasty is significantly more invasive than arthroscopy and patients understand the difference, so the results, even if valid, cannot be generalized to arthroplasty patients.

Finally, there are substantial problems with patient report measures; the addition of same day surgery assessment makes accurate outcome very unlikely.

The author did not receive any outside funding or grants in support of her research for or preparation of this work. Neither she nor a member of her immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of her immediate family, is affiliated or associated.

References:

1. Rosenthal, R. Experimenter Effects in Behavioral Research, enlarged ed. Irving Publications, New York. 1976.

2. Lingard EA. Commentary and perspective on: Patients can provide a valid assessment of quality of life, functional status, and general health on the day they undergo knee surgery (2008;90:264-70). 2008 Feb. http://www.ejbjs.org/Comments/2008/cp_feb08_lingard.det. Accessed 2 Feb 2008.