The scratch collapse test (SCT) is a provocative test described as an adjunct for diagnosing peripheral nerve compression. The utility of SCT has been investigated by other groups1,2 . The sensitivity and specificity ranges between (31-64%) and (61-99%) . The difference was thought to be due to variation in demographics between units.
To investigate the use of SCT in the New Zealand population at tertiary hand surgery referral centres.
Patients referred to hand clinic were collected prospectively and placed in 2 groups: 1) Patients referred with clinical signs of carpal tunnel syndrome (CTS), 2) patients with upper limb nerve symptoms with non-specific symptoms, with positive SCT at the posterior triangle.
For group 1, power analysis was performed to determine the number of patients required to show comparable sensitivity and specificity to previous studies1.Staff with no clinical symptoms of CTS were used as controls. Intraoperative nerve findings and resolution of nighttime symptoms at 6 weeks were used to confirm the diagnosis of CTS.
For group 2, after investigations were conducted to exclude nerve compression requiring surgical management, patients were referred to physiotherapy. Subjective and objective outcomes were assessed using the Michigan Hand Questionnaire.
N= 28(cases) (Group 1).Sensitivity and specificity were 29.6% and 99%. One patient with positive pronator teres SCT was found to have persistent symptoms despite a clinical diagnosis of CTS.
N=6 (Group 2). Two out of 6 patients treated have completed 3 months of follow up. Both patients showed significant improvement in symptoms.
The scratch collapse test has similar sensitivity and specificity in diagnosing CTS compared to other studies1.Utility of the SCT, however is more evident in the assessment of patients with vague or difficult symptoms. This is particularly useful in patients with posture related nerve irritation who might otherwise be discharged after negative conventional tests.