Introduction: Ultrasonography has emerged as an alternative tool for diagnosing peripheral neuropathies, such as carpal tunnel syndrome (CTS). Yet, data are still lacking as regards the diagnostic validity of the different ultrasonography measurements for detecting CTS in clinical settings.
Aims: To determine the diagnostic validity of ultrasound measurements of the cross-sectional area of the median nerve in the wrist (CSA-M) and of the ratio of the area of the median nerve between the wrist and the forearm (R-WF) in the diagnosis of CTS, using electroneuromyography (ENG) as the reference technique.
Patients and methods: Ultrasound measurements were performed on 59 subjects (100 wrists) who were referred to have an ENG due to suspected CTS. The examiners that performed the ultrasonography scan did not know the results of the ENG. The cut-off points were later calculated by means of ROC curves for each of the measurements (CSA-M and R-WF) and their diagnostic validity was analysed.
Results: With a cut-off point of 9.15 mm2, CSA-M measurement obtained a sensitivity of 75.81%, a specificity of 74.29%, a positive likelihood ratio of 2.95 and a negative likelihood ratio of 0.33. For the R-WF measurement and a cut-off point of 1.56, the values for sensitivity, specificity, and positive and negative likelihood ratios were 70.97%, 71.43%, 2.48 and 0.4, respectively.
Conclusions: Both the CSA-M and R-WF appear to be useful measures in the diagnosis of CTS, taking the ENG as a reference test.
Title: Validez diagnostica de la ecografia en el sindrome del tunel carpiano.
Introduccion. La ecografia ha emergido como una herramienta diagnostica alternativa de las neuropatias perifericas, como el sindrome del tunel carpiano (STC). Sin embargo, faltan datos sobre la validez diagnostica de las diferentes mediciones ecograficas para la deteccion del STC en entornos clinicos. Objetivo. Hallar la validez diagnostica de las mediciones ecograficas del area de seccion transversal del nervio mediano en la muñeca (AST-M) y de la ratio del area del nervio mediano entre la muñeca y el antebrazo (R-MA) en el diagnostico del STC, utilizando como tecnica de referencia el electroneurograma (ENG). Pacientes y metodos. Se realizaron mediciones ecograficas en 59 sujetos (97 muñecas) referidos para someterse a un ENG por sospecha de STC. Los examinadores que realizaron la ecografia desconocian los resultados del ENG. Posteriormente, se calcularon los puntos de corte mediante curvas ROC para cada una de las mediciones (AST-M y R-MA) y se analizo su validez diagnostica. Resultados. Con un punto de corte de 9,15 mm2, la medicion AST-M obtuvo una sensibilidad del 75,81%, una especificidad del 74,29%, una ratio de probabilidad positiva de 2,95 y una ratio de probabilidad negativa de 0,33. Para la medicion R-MA y un punto de corte de 1,56, los valores de sensibilidad, especificidad y ratios de probabilidad positiva y negativa fueron 70,97%, 71,43%, 2,48 y 0,4, respectivamente. Conclusion. Tanto el AST-M como la R-MA parecen ser medidas utiles en el diagnostico del STC tomando como prueba de referencia el ENG.