Abstract
IntroductionEarly diagnosis of intensive care unit – acquired weakness (ICU-AW) using the current reference standard, that is, assessment of muscle strength, is often hampered due to impaired consciousness. Biological markers could solve this problem but have been scarcely investigated. We hypothesized that plasma levels of neurofilaments are elevated in ICU-AW and can diagnose ICU-AW before muscle strength assessment is possible.MethodsFor this prospective observational cohort study, neurofilament levels were measured using ELISA (NfHSMI35 antibody) in daily plasma samples (index test). When patients were awake and attentive, ICU-AW was diagnosed using the Medical Research Council scale (reference standard). Differences and discriminative power (using the area under the receiver operating characteristic curve; AUC) of highest and cumulative (calculated using the area under the neurofilament curve) neurofilament levels were investigated in relation to the moment of muscle strength assessment for each patient.ResultsBoth the index test and reference standard were available for 77 ICU patients. A total of 18 patients (23%) fulfilled the clinical criteria for ICU-AW. Peak neurofilament levels were higher in patients with ICU-AW and had good discriminative power (AUC: 0.85; 95% CI: 0.72 to 0.97). However, neurofilament levels did not peak before muscle strength assessment was possible. Highest or cumulative neurofilament levels measured before muscle strength assessment could not diagnose ICU-AW (AUC 0.59; 95% CI 0.37 to 0.80 and AUC 0.57; 95% CI 0.32 to 0.81, respectively).ConclusionsPlasma neurofilament levels are raised in ICU-AW and may serve as a biological marker for ICU-AW. However, our study suggests that an early diagnosis of ICU-AW, before muscle strength assessment, is not possible using neurofilament levels in plasma.Electronic supplementary materialThe online version of this article (doi:10.1186/cc13699) contains supplementary material, which is available to authorized users.
Highlights
Diagnosis of intensive care unit – acquired weakness (ICU-AW) using the current reference standard, that is, assessment of muscle strength, is often hampered due to impaired consciousness
We investigated if neurofilaments could diagnose ICU-AW early, that is, before muscle strength assessment was possible
This study shows that neurofilament levels are elevated in patients with ICU-AW compared to patients without ICU-AW
Summary
Diagnosis of intensive care unit – acquired weakness (ICU-AW) using the current reference standard, that is, assessment of muscle strength, is often hampered due to impaired consciousness. Intensive Care Unit–acquired weakness (ICU-AW) is a frequent neuromuscular complication of critical illness [1]. ICU-AW has important implications for critically ill patients because mortality and (long-term) morbidity are increased in ICU-AW [1]. The current standard for diagnosing ICUAW is muscle strength assessment, quantified using the Medical Research Council (MRC) scale [2]. Muscle strength assessment is frequently delayed because of impaired consciousness or attentiveness, due to sedation or delirium [3]. It is important to diagnose ICU-AW early after onset of critical illness to initiate supportive interventions, such as early rehabilitation, which may improve functional outcome [4]. It is important to provide accurate prognostic information to patients, their families and physicians
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