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Letter response
Response to: ‘Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome’ by zhu and Liu
In summary, our data indicate that ultrasound is a good but not perfect diagnostic test for patients with suspected CTS. Apart from measurement of median nerve CSA and detection of intranerval PD signals, it provides the possibility to identify secondary causes of CTS, such as synovitis, tenosynovitis, abnormal masses or other abnormalities within the carpal tunnel.
Our and several previous studies demonstrated a high diagnostic value of ultrasound for carpal tunnel syndrome (CTS).1 2 Among the various abnormalities within the carpal tunnel reported, the increase of the cross-sectional area (CSA) of the median nerve is the most commonly studied ultrasound abnormality.3 Additionally, ultrasound allows the identification of secondary causes of CTS, such as synovitis, tenosynovitis, calcified masses or tophaceous gout, as pointed out by zhu et al.4 We acknowledge that the diagnostic value of ultrasound is not perfect, as some patients may suffer from CTS despite a normal ultrasound result and, vice versa, abnormal ultrasound findings do not necessarily indicate CTS.1 In these cases, additional tests, such as nerve conduction studies (although the sensitivity and specificity of this method are far away from 100% as shown in our and several other studies) are required to establish the final diagnosis.1 5 A specific aspect of our study is the determination of a relevant cut-off for the median nerve CSA. We decided to determine two cut-offs: one resulting in a ≥90% sensitivity implying that patients with a CSA below this limit are unlikely to suffer from CTS, and a second cut-off revealing a ≥90% specificity for the diagnosis. Decreasing the cut-off certainly increases the sensitivity (theoretically up to 100%), but at the cost of specificity and, conversely, increasing the cut-off would result in a better specificity. A perfect cut-off providing 100% sensitivity and specificity is unrealistic, and misclassification of a proportion of patients has, unfortunately, to be accepted.2 Another aspect to consider is the selection of the study population. One strength of our study is the focus on patients with suspected CTS, rather than investigating patients with established CTS and healthy controls (as it was performed in previous studies).2 6 Our results are, therefore, directly applicable to daily clinical routine, whereas studies investigating patients with known CTS and healthy controls were prone to result in artificially high diagnostic values. We were the first to investigate the value of intranerval Power Doppler (PD) signals as a diagnostic criterion for CTS diagnosis systematically.1 We observed a reasonable sensitivity and specificity and found this sign particularly valuable for patients with intermediate median nerve CSA. We acknowledge, however, that the sensitivity of PD depends on the power of the ultrasound device, and that our results may not be generalisable given that older and/or low-power machines are commonly used.7 Further validation studies using different devices are thus necessary to investigate the value of PD for CTS diagnosis.
Christian Dejaco,1 Martin Stradner,1 Dorothea Zauner,1 Werner Seel,2 Nicole Elisabeth Simmet,2 Alexander Klammer,1 Petra Heitzer,2 Kerstin Brickmann,1 Judith Gretler,1 Florentine Fürst-Moazedi,1 Rene Thonhofer,1,3 Rusmir Husic,1 Josef Hermann,1 Winfried B Graninger,1 Stefan Quasthoff2,4
Ann Rheum Dis April 2014 Vol 73 No 4
1
Department of Rheumatology and Immunology, Medical University Graz, Graz, Austria Department of Neurology, Medical University Graz, Graz, Austria 3 Department of Internal Medicine, General hospital Muerzzuschlag, Muerzzuschlag, Austria 4 Department of Neurology, General hospital of the Barmherzige Brüder Eggenberg, Graz, Austria 2
Correspondence to Dr Christian Dejaco, Department of Rheumatology and Immunology, Medical University Graz, Auenbruggerplatz 15, Graz A-8036, Austria; [email protected] Competing interests None. Provenance and peer review Commissioned; internally peer reviewed. To cite Dejaco C, Stradner M, Zauner D, et al. Ann Rheum Dis 2014;73:e17. Received 18 December 2013 Accepted 20 December 2013 Published Online First 9 January 2014
▸ http://dx.doi.org/10.1136/annrheumdis-2013-205015 Ann Rheum Dis 2014;73:e17. doi:10.1136/annrheumdis-2013-205038
REFERENCES 1
2
3
4 5 6
7
Dejaco C, Stradner M, Zauner D, et al. Ultrasound for diagnosis of carpal tunnel syndrome: comparison of different methods to determine median nerve volume and value of power Doppler sonography. Ann Rheum Dis 2013;72:1934–9. Fowler JR, Gaughan JP, Ilyas AM. The sensitivity and specificity of ultrasound for the diagnosis of carpal tunnel syndrome: a meta-analysis. Clin Orthop Relat Res 2011;469:1089–94. Mallouhi A, Pulzl P, Trieb T, et al. Predictors of carpal tunnel syndrome: accuracy of gray-scale and color Doppler sonography. AJR Am J Roentgenol 2006;186: 1240–5. zhu J, Liu F. Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome. Ann Rheum Dis 2014;73:e16. Seror P. Sonography and electrodiagnosis in carpal tunnel syndrome diagnosis, an analysis of the literature. Eur J Radiol 2008;67:146–52. Klauser AS, Halpern EJ, De Zordo T, et al. Carpal tunnel syndrome assessment with US: value of additional cross-sectional area measurements of the median nerve in patients versus healthy volunteers. Radiology 2009;250:171–7. Duftner C, Schüller-Weidekamm C, Mandl P, et al. Clinical implementation of musculoskeletal ultrasound in rheumatology in Austria. Rheumatol Int Published Online First: 26 September 2013. doi:10.1007/s00296-013-2863-4
e17
Downloaded from ard.bmj.com on September 26, 2014 - Published by group.bmj.com
Response to: 'Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome' by zhu and Liu Christian Dejaco, Martin Stradner, Dorothea Zauner, et al. Ann Rheum Dis 2014 73: e17 originally published online January 9, 2014
doi: 10.1136/annrheumdis-2013-205038
Updated information and services can be found at: http://ard.bmj.com/content/73/4/e17.full.html
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References
This article cites 5 articles, 1 of which can be accessed free at: http://ard.bmj.com/content/73/4/e17.full.html#ref-list-1
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Letter response
Response to: ‘Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome’ by zhu and Liu
In summary, our data indicate that ultrasound is a good but not perfect diagnostic test for patients with suspected CTS. Apart from measurement of median nerve CSA and detection of intranerval PD signals, it provides the possibility to identify secondary causes of CTS, such as synovitis, tenosynovitis, abnormal masses or other abnormalities within the carpal tunnel.
Our and several previous studies demonstrated a high diagnostic value of ultrasound for carpal tunnel syndrome (CTS).1 2 Among the various abnormalities within the carpal tunnel reported, the increase of the cross-sectional area (CSA) of the median nerve is the most commonly studied ultrasound abnormality.3 Additionally, ultrasound allows the identification of secondary causes of CTS, such as synovitis, tenosynovitis, calcified masses or tophaceous gout, as pointed out by zhu et al.4 We acknowledge that the diagnostic value of ultrasound is not perfect, as some patients may suffer from CTS despite a normal ultrasound result and, vice versa, abnormal ultrasound findings do not necessarily indicate CTS.1 In these cases, additional tests, such as nerve conduction studies (although the sensitivity and specificity of this method are far away from 100% as shown in our and several other studies) are required to establish the final diagnosis.1 5 A specific aspect of our study is the determination of a relevant cut-off for the median nerve CSA. We decided to determine two cut-offs: one resulting in a ≥90% sensitivity implying that patients with a CSA below this limit are unlikely to suffer from CTS, and a second cut-off revealing a ≥90% specificity for the diagnosis. Decreasing the cut-off certainly increases the sensitivity (theoretically up to 100%), but at the cost of specificity and, conversely, increasing the cut-off would result in a better specificity. A perfect cut-off providing 100% sensitivity and specificity is unrealistic, and misclassification of a proportion of patients has, unfortunately, to be accepted.2 Another aspect to consider is the selection of the study population. One strength of our study is the focus on patients with suspected CTS, rather than investigating patients with established CTS and healthy controls (as it was performed in previous studies).2 6 Our results are, therefore, directly applicable to daily clinical routine, whereas studies investigating patients with known CTS and healthy controls were prone to result in artificially high diagnostic values. We were the first to investigate the value of intranerval Power Doppler (PD) signals as a diagnostic criterion for CTS diagnosis systematically.1 We observed a reasonable sensitivity and specificity and found this sign particularly valuable for patients with intermediate median nerve CSA. We acknowledge, however, that the sensitivity of PD depends on the power of the ultrasound device, and that our results may not be generalisable given that older and/or low-power machines are commonly used.7 Further validation studies using different devices are thus necessary to investigate the value of PD for CTS diagnosis.
Christian Dejaco,1 Martin Stradner,1 Dorothea Zauner,1 Werner Seel,2 Nicole Elisabeth Simmet,2 Alexander Klammer,1 Petra Heitzer,2 Kerstin Brickmann,1 Judith Gretler,1 Florentine Fürst-Moazedi,1 Rene Thonhofer,1,3 Rusmir Husic,1 Josef Hermann,1 Winfried B Graninger,1 Stefan Quasthoff2,4
Ann Rheum Dis April 2014 Vol 73 No 4
1
Department of Rheumatology and Immunology, Medical University Graz, Graz, Austria Department of Neurology, Medical University Graz, Graz, Austria 3 Department of Internal Medicine, General hospital Muerzzuschlag, Muerzzuschlag, Austria 4 Department of Neurology, General hospital of the Barmherzige Brüder Eggenberg, Graz, Austria 2
Correspondence to Dr Christian Dejaco, Department of Rheumatology and Immunology, Medical University Graz, Auenbruggerplatz 15, Graz A-8036, Austria; [email protected] Competing interests None. Provenance and peer review Commissioned; internally peer reviewed. To cite Dejaco C, Stradner M, Zauner D, et al. Ann Rheum Dis 2014;73:e17. Received 18 December 2013 Accepted 20 December 2013 Published Online First 9 January 2014
▸ http://dx.doi.org/10.1136/annrheumdis-2013-205015 Ann Rheum Dis 2014;73:e17. doi:10.1136/annrheumdis-2013-205038
REFERENCES 1
2
3
4 5 6
7
Dejaco C, Stradner M, Zauner D, et al. Ultrasound for diagnosis of carpal tunnel syndrome: comparison of different methods to determine median nerve volume and value of power Doppler sonography. Ann Rheum Dis 2013;72:1934–9. Fowler JR, Gaughan JP, Ilyas AM. The sensitivity and specificity of ultrasound for the diagnosis of carpal tunnel syndrome: a meta-analysis. Clin Orthop Relat Res 2011;469:1089–94. Mallouhi A, Pulzl P, Trieb T, et al. Predictors of carpal tunnel syndrome: accuracy of gray-scale and color Doppler sonography. AJR Am J Roentgenol 2006;186: 1240–5. zhu J, Liu F. Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome. Ann Rheum Dis 2014;73:e16. Seror P. Sonography and electrodiagnosis in carpal tunnel syndrome diagnosis, an analysis of the literature. Eur J Radiol 2008;67:146–52. Klauser AS, Halpern EJ, De Zordo T, et al. Carpal tunnel syndrome assessment with US: value of additional cross-sectional area measurements of the median nerve in patients versus healthy volunteers. Radiology 2009;250:171–7. Duftner C, Schüller-Weidekamm C, Mandl P, et al. Clinical implementation of musculoskeletal ultrasound in rheumatology in Austria. Rheumatol Int Published Online First: 26 September 2013. doi:10.1007/s00296-013-2863-4
e17
Downloaded from ard.bmj.com on September 26, 2014 - Published by group.bmj.com
Response to: 'Paying attention to carpal tunnel contents lesions: ultrasound for evaluation of carpal tunnel syndrome' by zhu and Liu Christian Dejaco, Martin Stradner, Dorothea Zauner, et al. Ann Rheum Dis 2014 73: e17 originally published online January 9, 2014
doi: 10.1136/annrheumdis-2013-205038
Updated information and services can be found at: http://ard.bmj.com/content/73/4/e17.full.html
These include:
References
This article cites 5 articles, 1 of which can be accessed free at: http://ard.bmj.com/content/73/4/e17.full.html#ref-list-1
Email alerting service
Topic Collections
Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections Clinical diagnostic tests (1120 articles) Radiology (988 articles) Radiology (diagnostics) (679 articles) Degenerative joint disease (3977 articles) Genetics (836 articles) Musculoskeletal syndromes (4252 articles)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions
To order reprints go to: http://journals.bmj.com/cgi/reprintform
To subscribe to BMJ go to: http://group.bmj.com/subscribe/
