title: Diagnostic accuracy of quantitative neuromuscular ultrasound for the diagnosis of intensive care unit-acquired weakness: a cross-sectional observational study.
abstract: BACKGROUND
  Neuromuscular ultrasound is a noninvasive investigation, which can be easily performed at the bedside on the ICU. A reduction in muscle thickness and increase in echo intensity over time have been described in ICU patients, but the relation to ICU-acquired weakness (ICU-AW) is unknown. We hypothesized that quantitative assessment of muscle and nerve parameters with ultrasound can differentiate between patients with and without ICU-AW. The aim of this cross-sectional study was to investigate the diagnostic accuracy of neuromuscular ultrasound for diagnosing ICU-AW.
  
  
  METHODS
  Newly admitted ICU patients, mechanically ventilated for at least 48 h, were included. As soon as patients were awake and attentive, an ultrasound was made of four muscles and two nerves (index test) and ICU-AW was evaluated using muscle strength testing (reference standard; ICU-AW defined as mean Medical Research Council score <4). Diagnostic accuracy of muscle thickness, echo intensity and homogeneity (echo intensity standard deviation) as well as nerve cross-sectional area, thickness and vascularization were evaluated with the area under the curve of the receiver operating characteristic curve (ROC-AUC). We also evaluated diagnostic accuracy of z-scores of muscle thickness, echo intensity and echo intensity standard deviation.
  
  
  RESULTS
  Seventy-one patients were evaluated of whom 41 had ICU-AW. Ultrasound was done at a median of 7 days after admission in patients without ICU-AW and 9 days in patients with ICU-AW. Diagnostic accuracy of all muscle and nerve parameters was low. ROC-AUC ranged from 51.3 to 68.0% for muscle parameters and from 51.0 to 66.7% for nerve parameters.
  
  
  CONCLUSIONS
  Neuromuscular ultrasound does not discriminate between patients with and without ICU-AW at the time the patient awakens and is therefore not able to reliably diagnose ICU-AW in ICU patients relatively early in the disease course.
authors.affiliation: Department of Intensive Care Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. e.witteveen@amc.nl.|Laboratory of Experimental Anesthesiology and Intensive Care (L·E·I·C·A), Academic Medical Center, Amsterdam, The Netherlands. e.witteveen@amc.nl.|Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands. e.witteveen@amc.nl.
authors.forename: Esther
authors.initials: E
authors.lastname: Witteveen
authors.affiliation: Department of Rehabilitative Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Juultje
authors.initials: J
authors.lastname: Sommers
authors.affiliation: Department of Intensive Care Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.|Laboratory of Experimental Anesthesiology and Intensive Care (L·E·I·C·A), Academic Medical Center, Amsterdam, The Netherlands.|Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Luuk
authors.initials: L
authors.lastname: Wieske
authors.affiliation: Department of Neurology and Clinical Neurophysiology, Donders Center for Neuroscience, Radboud University Medical Center, Nijmegen, The Netherlands.|Department of Intensive Care Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Jonne
authors.initials: J
authors.lastname: Doorduin
authors.affiliation: Department of Neurology and Clinical Neurophysiology, Donders Center for Neuroscience, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Nens
authors.initials: N
authors.lastname: van Alfen
authors.affiliation: Department of Intensive Care Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.|Laboratory of Experimental Anesthesiology and Intensive Care (L·E·I·C·A), Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Schultz
authors.affiliation: Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Ivo N
authors.initials: IN
authors.lastname: van Schaik
authors.affiliation: Department of Intensive Care Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.|Laboratory of Experimental Anesthesiology and Intensive Care (L·E·I·C·A), Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Janneke
authors.initials: J
authors.lastname: Horn
authors.affiliation: Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Camiel
authors.initials: C
authors.lastname: Verhamme
keywords: Critical illness myopathy; Critical illness neuromyopathy; Critical illness polyneuropathy; Diagnosis; ICU-AW; Neuromuscular ultrasound