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Mortality Prediction in Acute Respiratory Distress Syndrome.

To the Editor: In a recent issue of Critical Care Medicine, Villar et al (1) reported an outcome prediction score in acute respiratory distress syndrome (ARDS) based on airway pressure, Fio 2 , Pao 2 , and age. These are the components of the “oxygenation index” (OI) which we described in 1989 (2). At that time, it was designed for neonates but has been applied to many patient groups including ARDS since then. In 2013, we reported an outcome prediction score for ARDS based on the OI and age (3). The score by Villar et al (1) is called “APPS,” (age, Pao 2 /Fio 2 ratio, and plateau pressure [Pplat]) and the score by Dechert et al (3) is called “AOI” (adjusted OI). The sensitivity and specificity of the AOI and the APPS are essentially the same. Both scores allow identification of low, medium, and high risk early after onset in ARDS. The AOI is derived from retrospective analysis of the ARDSNetwork (ARDSnet) database, predicting 28-day mortality. The authors reply: We thank Ohki et al (1) for their interest in our publication (2). In our study, we assessed validity and reliability of the Pediatric Confusion Assessment Method for the ICU (pCAM-ICU), the Pediatric Anesthesia Emergence Delirium (PAED) scale, and the newly developed severity scale for the pCAM-ICU (sspCAM-ICU) in critically ill patients 5 years old or older. We applied daily repeated assessments in the same patient to mimic the use of scores in clinical routine. We found that the overall sensitivity of the sspCAM-ICU (71.8%) was higher than that of the pCAM-ICU (52.3%) and the PAED scale (35.9%). PAED, pCAM-ICU, and sspCAM-ICU assessments were performed by trained physicians, who were not involved in the routine care of study patients. We agree with Ohki et al (1) that our data do not prove the feasibility of sspCAM-ICU ratings in clinical routine. Still, the study results allow the conclusion that the test validity of the sspCAM-ICU is superior compared to that of the pCAM-ICU and the PAED score when performed in a research setting. The next step would be to evaluate the feasibility of sspCAM-ICU scorings in routine care. However, investigators have to ensure adequate training of nurses and physicians to gain valuable knowledge from these studies. Lack of training or the use of ineffective teaching methods may result in poor test performance (3) and low implementation rates (4). We, therefore, would never recommend using any of these diagnostic tools without appropriate training. In contrast to the pCAM-ICU, which uses a nominal scale (e.g., inattention present/not present, feature 2), the sspCAMICU assigns symptoms to an ordinal scale which might have compromised interrater reliability. In fact, when considering patients with a sspCAM-ICU of greater than or equal to 6 points as delirium positive, the interrater reliability was similar to that of the pCAM-ICU (κ = 0.91). This analysis only includes 42 paired observations. Therefore, interrater reliability of the sspCAM-ICU should be reevaluated in larger multicenter trials. Finally, as Ohki et al (1) state, potential confounders that might have an influence on the validity of delirium scores should be prospectively assessed and incorporated in the analysis. We determined the effect of the depth of sedation, the status of mechanical ventilation, age, and gender on the validity of the sspCAM-ICU by calculating covariate-adjusted receiver operating characteristic (ROC) curves. We used a multivariate linear regression model by specifying covariates for the control population (Diagnostic and Statistical Manual-IV-Text Revision [DSM-IV-TR] negative patients) as well as the case population (DSM-IV-TR positive patients) (5). The analysis unveiled that sedation, mechanical ventilation, and increasing age had a significant negative effect on the validity of the sspCAM-ICU. Furthermore, being female had a significant positive effect on sspCAM-ICU’s ROC curve. We agree with Ohki et al (1) that there might be other covariates that have affected diagnostic performance of the DOI: 10.1097/CCM.0000000000002168 sspCAM-ICU. More studies are needed to further investigate which score to use in different patient cohorts. Dr. Luetz received funding from Köhler Chemie (payment for lecture) and from Orion Pharma (payment for lecture). Dr. Spies disclosed outside of the submitted work. She received additional grants from Grünenthal, Roche, MSD, Outcome Europe Sàrl, B. Braun Melsungen, BDA, BMBF, DKH, DLR, German Research Society, GIZ, Inner University Grants, Stifterverband, and European Commission; personal fees from ConvaTec International Service GmbH, Pfizer Pharma, Vifor Pharma, Fresenius Kabi, and Georg Thieme Verlag. Outside the submitted work, she has a patent (1