Supplementary Material for: Auditing Neonatal Intensive Care: Is PREM a Good Alternative to CRIB for Mortality Risk Adjustment in Premature Infants?

<b><i>Background:</i></b> Comparing outcomes at different neonatal intensive care units (NICUs) requires adjustment for intrinsic risk. The Clinical Risk Index for Babies (CRIB) is a widely used risk model, but it has been criticized for being affected by therapeutic decisions. The Prematurity Risk Evaluation Measure (PREM) is not supposed to be prone to treatment bias, but has not yet been validated. <b><i>Objectives:</i></b> We aimed to validate the PREM, compare its accuracy to that of the original and modified versions of the CRIB and CRIB-II, and examine the congruence of risk categorization. <b><i>Methods:</i></b> Very-low-birth-weight (VLBW) infants with a gestational age (GA) &lt;33 weeks, who were admitted to NICUs in Baden-Württemberg from 2003 to 2008, were identified from the German neonatal quality assurance program. CRIB, CRIB-II and PREM scores were calculated and modified. Omitting variables that directly reflected therapeutic decisions [the applied fraction of inspired oxygen (FiO₂)] or that may have been prone to early-treatment bias (base excess and temperature), non-NICU-therapy-influenced scores were obtained. Score performance was assessed by the area under their ROC curve (AUC). <b><i>Results:</i></b> The CRIB showed the largest AUC (0.89), which dropped significantly (to 0.85) after omitting the FiO₂. The PREM birth condition model, PREM(bcm) (AUC 0.86), and the PREM birth model, PREM(bm) (AUC 0.82), also demonstrated good discrimination. PREM(bm) was superior to other non-therapy-affected scores and to GA, particularly in infants with &lt;750 g birth weight. Congruence of risk categorization was low, especially among higher-risk cases. <b><i>Conclusions:</i></b> The CRIB score had the largest AUC, resulting from its inclusion of FiO₂. PREM(bm), as the most accurate score among those unaffected by early treatment, seems to be a good alternative for strict risk adjustment in NICU auditing. It could be useful to combine scores.

<b><i>背景：</i></b> 比较不同新生儿重症监护病房（Neonatal Intensive Care Unit, NICU）的治疗结局时，需对其固有风险进行校正。婴儿临床风险指数（Clinical Risk Index for Babies, CRIB）是目前应用广泛的风险模型，但因其易受治疗决策影响而受到诟病。早产风险评估量表（Prematurity Risk Evaluation Measure, PREM）理论上不易受治疗偏倚影响，但尚未得到验证。<b><i>目的：</i></b> 本研究旨在验证早产风险评估量表（PREM）的有效性，将其与原版及改良版婴儿临床风险指数（CRIB）、CRIB-II的预测准确性进行对比，并分析风险分层的一致性。<b><i>方法：</i></b> 本研究从德国新生儿质量保障项目中筛选出2003年至2008年在巴登-符腾堡州各NICU收治的胎龄（Gestational Age, GA）<33周的极低出生体重儿（Very-Low-Birth-Weight, VLBW）。计算并改良婴儿临床风险指数（CRIB）、CRIB-II及早产风险评估量表（PREM）的评分：剔除直接反映治疗决策的变量——吸入氧分数（applied fraction of inspired oxygen, FiO₂），以及可能受早期治疗偏倚影响的变量——碱剩余（base excess）与体温，得到不受NICU治疗方案影响的评分。采用受试者工作特征曲线下面积（Area Under the ROC Curve, AUC）评估各评分的预测性能。<b><i>结果：</i></b> 婴儿临床风险指数（CRIB）的受试者工作特征曲线下面积（AUC）最大，为0.89；剔除吸入氧分数（FiO₂）后，其AUC显著降至0.85。早产风险评估量表出生状况模型（PREM birth condition model, PREM(bcm)，AUC=0.86）与早产风险评估量表出生模型（PREM birth model, PREM(bm)，AUC=0.82）同样展现出良好的区分度。其中PREM(bm)的预测性能优于其他不受治疗影响的评分及胎龄（GA），尤其在出生体重<750g的婴儿中表现突出。风险分层的一致性较低，尤其是在高风险病例中。<b><i>结论：</i></b> 婴儿临床风险指数（CRIB）因纳入吸入氧分数（FiO₂）而拥有最大的AUC值。早产风险评估量表出生模型（PREM(bm)）作为不受早期治疗影响的评分中预测准确性最高的工具，或可作为新生儿重症监护病房审计中严格风险校正的良好替代方案。联合使用多种评分量表可能具有应用价值。