Abstract
Introduction: In diagnosing carpal tunnel syndrome (CTS) there is no consensus about the upper limit of normal (ULN) of the cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet. A previous study showed wrist circumference is the most important independent predictor for the ULN. In this study we optimised a wrist circumference-dependent ULN equation for optimal diagnostic accuracy and compared it to the generally used fixed ULN of 11 mm2.Methods: CSA and wrist circumference were measured in a prospective cohort of 253 patients (clinically defined CTS) and 96 healthy controls. An equation for the ULN for CSA was developed by means of univariable regression analysis. We calculated z-scores for all patients and healthy controls, and analysed these scores in a ROC curve and a decision plot. Sensitivity and specificity were determined and compared to fixed ULN values.Results: We found augmented diagnostic accuracy of our newly developed equation y = 0.88 * x −4.0, where y = the ULN of the CSA and x = wrist circumference. This equation has a corresponding sensitivity and specificity of 75% compared to a sensitivity of 70% while using a fixed cut-off value of 11 mm2 (p = 0.015).Conclusion: Optimising the regression equation for wrist circumference-dependent ULN cross-sectional area of the median nerve at the wrist inlet might improve diagnostic accuracy of ultrasonography in patients with carpal tunnel syndrome and seems to be more accurate than using fixed cut-off values.
Highlights
In diagnosing carpal tunnel syndrome (CTS) there is no consensus about the upper limit of normal (ULN) of the cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet
We previously showed a strong correlation between wrist circumference and CSA of the median nerve at the carpal tunnel inlet in subjects without signs or symptoms of carpal tunnel syndrome [15]
Diagnostic accuracy of US in Carpal tunnel syndrome (CTS) patients depends on the upper limit of normal of the measured CSA of the median nerve at the carpal tunnel inlet
Summary
In diagnosing carpal tunnel syndrome (CTS) there is no consensus about the upper limit of normal (ULN) of the cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet. Using ultrasonographic evaluation of increase in size of the median nerve at the carpal tunnel, fixed values for the upper limit of normal (ULN) with a broad range of 8.5–15 mm are reported [6,7,8,9,10,11,12,13,14]. This broad range of the normal values may be affected by morphometric factors, as well as age and sex as described in the literature [15,16,17,18]. Because of comparable sensitivity and patient-friendliness, ultrasonography is recommended as the first line diagnostic test for CTS in The Netherlands
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
