Background: The combined sensory index (CSI) test is more precise in diagnosing carpal tunnel syndrome (CTS) early cases. Another useful tool for early detection of CTS is the diagnostic ultrasonography. Objective: The present study was conducted to compare between the CSI test and its sensitivity with diagnostic ultrasonography IOR (inlet outlet ratio) in suspected or early cases of carpal tunnel syndrome (CTS). Patients and methods: The presentcase-control study involved 20 subjects with signs and symptoms suggestive of early cases of CTS with duration less than 6 months, in addition to 20 apparently healthy subjects who were clinically examined and underwent EDX and US evaluation. We excluded patients with severe CTS, proximal cervical lesion, or other neurological diseases. Results: By comparison, CSI shows a higher sensitivity than IOR. Combining both tests induced elevated substantial differences between patients as well as controls (P <0.01), besides elevating the sensitivity to 100%. Conclusion: It could be concluded that the sensitivity and accuracy of CSI is higher than diagnostic ultrasonographyIOR on the median nerve. On the contrary, diagnostic ultrasonographycan detect the anatomical abnormalities of the median nerve while the physiological abnormalities of the median nerve and their level can be examined by nerve conduction studies (NCS). They are complementary tests for CTS diagnosis