Open AccessDiagnostic value of sonography in patients with suspected carpal tunnel syndrome: A prospective study
Author(s) -
Ziswiler HansRudolf,
Reichenbach Stephan,
Vögelin Esther,
Bachmann Lucas M.,
Villiger Peter M.,
Jüni Peter
Publication year - 2005
Publication title -
arthritis & rheumatism
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/art.20723
Subject(s) - carpal tunnel syndrome , medicine , cutoff , receiver operating characteristic , concordance , nerve conduction study , prospective cohort study , nerve conduction , carpal tunnel , median nerve , pre and post test probability , nuclear medicine , likelihood ratios in diagnostic testing , positive predicative value , radiology , surgery , predictive value , physics , quantum mechanics
Objective To determine the diagnostic value of sonography in patients with suspected carpal tunnel syndrome (CTS). Methods We conducted a prospective study of 110 wrists in 74 consecutive patients with suspected CTS who had been referred to a tertiary care center. We determined the largest cross‐sectional area of the median nerve at the carpal tunnel. Because of the lack of a universally accepted reference standard, we first examined the association of sonography with nerve conduction. Then, we compared sonography with a reference standard based on the combination of nerve conduction studies and signs and symptoms. Sonography and reference standard tests were performed independently and interpreted under blinded conditions. Based on a fitted receiver operating characteristic curve, we estimated likelihood ratios (LRs) and posttest probabilities for different cutoffs. Results There was a high concordance between sonography and nerve conduction. Based on the combined reference standard, a cutoff of 10 mm 2 resulted in approximately equal sensitivity and specificity, but only moderate LRs. A cutoff of <8 mm 2 had satisfactory power to rule out CTS: the fitted‐negative LR was 0.13. Conversely, a cutoff of ≥12 mm 2 had excellent power to rule in CTS, with a fitted‐positive LR of 19.9. For nerves ≥12 mm 2 and a pretest probability of 70% expected in patients with suspected CTS in tertiary care, we found a posttest probability of CTS of 98%. Conclusion Depending on setting and purpose, different cutoff values for the largest cross‐sectional area may be used to accurately rule in or rule out CTS. Using sonography as a first‐line test may cost‐effectively reduce the number of nerve conduction studies in patients with suspected CTS. A large‐scale, randomized controlled trial is required to determine the effects of sonography on clinical outcomes, the number of nerve conduction studies performed, and the total cost.