Supplementary Material for: Physical Fitness as a Prognostic Marker for Infectious Events in Kidney Transplant Recipients

Introduction: Infectious events are one of the leading causes of death in kidney transplant recipients (KTRs). KTRs have reduced cardiorespiratory fitness (CRF), a predictor for infections in other populations. The aim of this study was to investigate whether CRF and muscle strength are prognostic markers for infectious events in KTRs. Methods: In this retrospective cohort study, 155 KTRs underwent an incremental, maximal cardiopulmonary exercise test (CPET) 3 months after transplantation. CRF was analyzed with peak oxygen consumption (VO2 peak) while muscle strength with isometric handgrip (HG) test. Laboratory blood samples and drug therapy were collected. The median follow-up period was 54 (interquartile range 38–62) months. Cox regression analyses were performed to evaluate predictors of infectious events adjusting for potential confounders. Results: During this study, severe infectious events occurred in 41 subjects (26.5%). 15.5% (n = 24) of patients had a severely reduced CRF, defined as a VO2 peak below the 5th percentile of the reference values reported for a matched healthy population. The hazard ratio for infectious events in this subgroup was 2.389 (95% CI = 1.188–4.801, p = 0.014), independently of gender, age, BMI, time on dialysis, hemoglobin concentration, eGFR, diabetes, and immunosuppressive regimen. On the contrary, no significant association of HG strength and infections was found. Conclusion: Therefore, low CRF may be considered as a modifiable predictor of severe infectious events in KTRs. A CPET should thus be recommended for cardiovascular screening, evaluation of CRF, and tailored exercise prescription to reduce the risk of infections and potentially improve long-term outcomes of transplantation.

引言：感染事件是肾移植受者（kidney transplant recipients, KTRs）的主要致死原因之一。肾移植受者存在心肺适能（cardiorespiratory fitness, CRF）下降的情况，而心肺适能是其他人群感染风险的预测因子。本研究旨在探讨心肺适能与肌肉力量能否作为肾移植受者感染事件的预后标志物。
方法：本研究为回顾性队列研究，共纳入155名肾移植受者，于移植术后3个月为其实施递增负荷极量心肺运动试验（cardiopulmonary exercise test, CPET）。以峰值摄氧量（peak oxygen consumption, VO2 peak）评估心肺适能，以等长握力（isometric handgrip, HG）试验评估肌肉力量。同时收集实验室血液样本与药物治疗方案信息。中位随访时间为54个月（四分位间距38~62个月）。采用Cox回归分析，校正潜在混杂因素后评估感染事件的预测因子。
结果：研究期间，共41名受试者（26.5%）发生严重感染事件。15.5%（n=24）的患者存在严重心肺适能下降，定义为峰值摄氧量低于匹配健康人群参考值的第5百分位数。该亚组患者感染事件的风险比为2.389（95%置信区间：1.188~4.801，p=0.014），且该关联独立于性别、年龄、体质量指数（BMI）、透析时长、血红蛋白浓度、估算肾小球滤过率（estimated glomerular filtration rate, eGFR）、糖尿病与免疫抑制方案。与之相反，未发现握力与感染事件存在显著关联。
结论：因此，低心肺适能可被视为肾移植受者发生严重感染事件的可干预预后预测因子。临床应推荐将心肺运动试验用于心血管筛查、心肺适能评估以及个体化运动处方制定，以降低感染风险，潜在改善移植术后长期预后。