Impact of using the International Risk Scoring Tool on the cost-utility of palivizumab for preventing severe respiratory syncytial virus infection in Canadian moderate-to-late preterm infants

To assess the cost-utility of palivizumab versus no prophylaxis in preventing severe respiratory syncytial virus (RSV) infection in Canadian moderate-to-late preterm (32–35 weeks’ gestational age) infants using an (i) International Risk Scoring Tool (IRST) and (ii) Canadian RST (CRST). A decision tree was developed to assess cost-utility. Infants assessed at moderate- and high-risk of RSV-related hospitalization (RSVH) by the IRST or CRST received palivizumab or no prophylaxis and then progressed to either (i) RSVH; (ii) emergency room/outpatient medically attended RSV-infection (MARI) or (iii) were uninfected/non-medically attended. Infants admitted to intensive care could incur mortality (0.43%). Respiratory morbidity was accounted in all uninfected surviving infants for 6 years or 18 years (RSVH/MARI). Palivizumab efficacy (72.2% RSVH reduction) and hospital outcomes were from the Canadian CARESS, PICNIC and RSV-Quebec studies. Palivizumab costs (50 mg: CAN$752; 100 mg: $1,505) were calculated from Canadian birth statistics combined with a growth algorithm. Healthcare/payer and societal costs (May 2022; 1.5% discounting) were included. Cost per quality-adjusted life year (QALY) was $29,789 with the IRST (0.79 probability of being Palivizumab was highly cost-effective (vs no prophylaxis) in Canadian moderate-to-late preterm infants using either the IRST or CRST. The IRST has fewer risk factors than the CRST (3 vs 7, respectively), captures more potential RSVHs (85% vs 54%) and provides another option to guide cost-effective RSV prophylaxis in Canada.

本研究旨在借助(i)国际风险评分工具（IRST）与(ii)加拿大风险评分工具（CRST），评估帕利珠单抗（palivizumab）相较于无预防措施，在预防加拿大胎龄32~35周的中晚期早产婴儿发生重症呼吸道合胞病毒（RSV）感染中的成本效用。本研究构建决策树模型以开展成本效用评估：经IRST或CRST评估为RSV相关住院（RSVH）中高风险的早产儿，将接受帕利珠单抗预防或不采取预防措施，后续转归分为三类：(i) 发生RSVH；(ii) 出现急诊科/门诊就医的呼吸道合胞病毒感染（MARI）；(iii) 未感染/未就医。入住重症监护室的患儿可能发生死亡，死亡率为0.43%。本研究对所有存活的未感染患儿，以及发生RSVH或MARI的患儿，均核算其6年或18年随访期内的呼吸道疾病发病情况。帕利珠单抗的疗效（可降低72.2%的RSVH发生风险）及住院转归数据源自加拿大CARESS、PICNIC及RSV-Quebec三项研究。帕利珠单抗的给药成本（50mg规格：752加元；100mg规格：1505加元）基于加拿大出生统计数据结合生长算法计算得出。本研究纳入医疗保健/支付方及社会层面的成本（数据截至2022年5月，贴现率为1.5%）。采用IRST时，每质量调整生命年（QALY）的成本为29789加元（成本效益概率为0.79）；无论采用IRST还是CRST，帕利珠单抗用于加拿大中晚期早产婴儿的预防均较不采取预防措施具有极高的成本效益。相较于CRST，IRST的风险因素更少（分别为3项与7项），可识别更多潜在RSVH病例（85% vs 54%），可为加拿大开展具有成本效益的RSV预防提供另一项可选方案。