The Therapy Intensity Level scale for traumatic brain injury: clinimetric assessment on neuro-monitored patients across 52 European intensive care units

Abstract

The Therapy Intensity Level (TIL) scale and its abridged version (TIL(Basic)) are used to record the intensity of daily management for raised intracranial pressure (ICP) after traumatic brain injury (TBI). However, it is uncertain: (1) whether TIL is valid across the wide variation in modern ICP treatment strategies, (2) if TIL performs better than its predecessors, (3) how TIL’s component therapies contribute to the overall score, and (4) whether TIL(Basic)may capture sufficient information. We aimed to answer these questions by assessing TIL on a contemporary population of ICP-monitored TBI patients (n=873) in 52 intensive care units (ICUs) across 18 European countries and Israel. From the observational, prospective Collaborative European NeuroTrauma Effectiveness Research in TBI (CENTER-TBI) study, we extracted first-week daily TIL scores (TIL24), ICP values, physician-based impressions of aberrant ICP, clinical markers of injury severity, and six-month functional outcome scores. We evaluated the construct and criterion validity of TIL against that of its predecessors, an unweighted version of TIL, and TIL(Basic). We calculated the median score of each TIL component therapy for each total score as well as associations between each component score and markers of injury severity. Moreover, we calculated the information coverage of TIL by TIL(Basic), defined by the mutual information of TIL and TIL(Basic)divided by the entropy of TIL. The statistical validity measures of TIL were significantly greater or similar to those of alternative scales, and TIL integrated the widest range of modern ICP treatments. First-week median TIL24(TILmedian) outperformed first-week maximum TIL24(TILmax) in discriminating refractory intracranial hypertension (RIC) during ICU stay, and the thresholds which maximised the sum of sensitivity and specificity for RIC detection were TILmedian≥7.5 (sensitivity: 81% [95% CI: 77–87%], specificity: 72% [95% CI: 70–75%]) and TILmax≥14 (sensitivity: 68% [95% CI: 62–74%], specificity: 79% [95% CI: 77–81%]). The sensitivity-specificity-optimising TIL24threshold for detecting surgical ICP control was TIL24≥9 (sensitivity: 87% [95% CI: 83–91%], specificity: 74% [95% CI: 72–76%]). The median component scores for each TIL24reflected a credible staircase approach to treatment intensity escalation, from head positioning to surgical ICP control, as well as considerable variability in the use of cerebrospinal fluid drainage and decompressive craniectomy. First-week maximum TIL(Basic)(TIL(Basic)max) suffered from a strong ceiling effect and could not replace TILmax. TIL(Basic)24and first-week median TIL(Basic)(TIL(Basic)median) could be a suitable replacement for TIL24and TILmedian, respectively (up to 33% [95% CI: 31–35%] information coverage). Numerical ranges were derived for categorising TIL24scores into TIL(Basic)24scores. Our results validate the TIL scale across a spectrum of ICP management and monitoring approaches and support its use as an intermediate outcome after TBI.