Supplementary Material for: The Italian Version of the Brief 21-Item Prodromal Questionnaire: Field Test, Psychometric Properties and Age-Sensitive Cut-Offs

<b><i>Background:</i></b> The Brief, 21-item version of the Prodromal Questionnaire (PQ-B) is a promising screener for psychosis-risk states that could be implemented in routine clinical practice. In this study, we assessed psychometric properties of the Italian version of the PQ-B (iPQ-B) in a sample of 243 help-seekers, aged 13–35 years. <b><i>Sampling and Methods:</i></b> After completing the iPQ-B, participants were assessed with the Comprehensive Assessment of At-Risk Mental States (CAARMS). Diagnostic accuracy (sensitivity, specificity, positive and negative predictive values [PPV and NPV], positive and negative likelihood ratios) and concurrent validity between PQ-B and CAARMS were determined using Cronbach’s alpha and Cohen’s kappa. We also tested the validity of the adopted PQ-B cut-offs through Receiver Operating Characteristic (ROC) curves plotted against CAARMS diagnoses and the predictive validity of the iPQ-B at 1-year follow-up. <b><i>Results:</i></b> The iPQ-B showed high internal consistency (Cronbach’s alpha = 0.868), acceptable diagnostic accuracy and concurrent validity (70% sensitivity, 67% specificity, 81% PPV, Cohen’s kappa = 0.335). ROC analyses pointed to threshold of ≥20 on the PQ-B total distress score as best cut-off. After 12 months of follow-up, 11% of participants who scored ≥4 on the PQ-B distressing item total score and did not meet CAARMS psychosis criteria at baseline, developed a psychotic disorder. Interestingly, age had significant negative correlations with iPQ-B scores and adolescents (aged &lt; 18 years) showed higher iPQ-B scores than young adults. <b><i>Conclusions:</i></b> Overall, the psychometric properties of the iPQ-B were satisfactory. As iPQ-B scores appeared inversely associated to age, age-tailored cut-off scores are recommended for screening purposes in child-adolescent cohorts.

**<i>研究背景：</i>** 21项版简易前驱症状问卷（Prodromal Questionnaire, PQ-B）是一款颇具应用前景的精神病风险状态筛查工具，可应用于常规临床实践。本研究针对243名年龄13至35岁的求助者样本，评估了意大利版PQ-B（iPQ-B）的心理测量学特性。**<i>研究对象与方法：</i>** 完成意大利版PQ-B问卷后，采用高危精神状态综合评估量表（Comprehensive Assessment of At-Risk Mental States, CAARMS）对参与者进行评估。本研究通过克朗巴赫α系数与科恩kappa值，分析PQ-B与CAARMS间的诊断准确度（灵敏度、特异度、阳性与阴性预测值[PPV与NPV]、阳性与阴性似然比）及同时效度；此外，通过以CAARMS诊断为参照的受试者工作特征（Receiver Operating Characteristic, ROC）曲线，验证了PQ-B既定临界值的效度，并评估了iPQ-B在1年随访中的预测效度。**<i>研究结果：</i>** iPQ-B展现出良好的内部一致性（克朗巴赫α系数=0.868），诊断准确度与同时效度均较为可观：灵敏度70%、特异度67%、阳性预测值81%，科恩kappa值为0.335。ROC分析显示，PQ-B总痛苦得分≥20为最佳临界值。随访12个月后，基线时PQ-B痛苦条目总得分≥4且未达到CAARMS精神病性标准的参与者中，有11%发展为精神病性障碍。值得注意的是，年龄与iPQ-B得分呈显著负相关，青少年（年龄<18岁）的iPQ-B得分显著高于青年群体。**<i>研究结论：</i>** 总体而言，iPQ-B的心理测量学特性令人满意。鉴于iPQ-B得分与年龄呈负相关，建议针对儿童青少年队列的筛查工作采用年龄适配的临界得分。