Sarcopenia is a condition of low muscle strength and quantity, severe if low physical performances. The sarcopenia index (SI), calculated by blood levels of creatinine and cystatin C, had been reported to be correlated with skeletal muscle mass and is a potential simple screening tool for sarcopenia. We hypothesized that patients with a low SI, meaning low muscle mass, would have an inflated estimated glomerular filtration rate (eGFR) value based on serum creatinine levels. We also tested the prognostic value of the SI in a cohort of patients who had surgery for renal malignancies. We conducted a retrospective, observational study of 322 patients that had surgery for renal tumors in National Cancer Center Hospital East (Kashiwa, Chiba) between April 2017 and June 2023. We assessed sarcopenia measuring psoas muscle index (PMI), psoas muscle density (PMD), and skeletal muscle area (SMA) by computed tomography. We assessed the association between SI and eGFR before and after surgery. We also assessed the association between SI and postoperative outcome, including overall survival. Of the 322 patients, 211 (66%) were males, with a median age of 69 years. SI had a weak correlation with both PMI and PMD in males (PMI: ρ = 0.25; PMD: ρ = 0.21). In females, SI and PMD exhibited a low correlation (ρ = 0.26), while SI and PMI displayed an insignificant correlation (ρ = 0.19). The correlation between SMA and SI was moderate for both males and females (males: ρ = 0.51; females: ρ = 0.46). After radical nephrectomy, eGFR decreased in 98% of patients with high SI, compared to 69% of patients with low SI. We also demonstrated that low SI predicted poor prognosis. Clinicians can recognize the possibility of overestimated eGFR in the low SI group by measuring SI around the surgery. Low SI may also help predict poor prognosis.

中文翻译：

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基于胱抑素 C 的肌肉减少症指数在肾肿瘤手术患者中的价值

肌肉减少症是一种肌肉力量和数量低下的病症，如果身体机能低下，则严重。据报道，肌肉减少症指数 (SI) 通过血液肌酐和胱抑素 C 水平计算得出，与骨骼肌质量相关，是肌肉减少症潜在的简单筛查工具。我们假设 SI 较低（即肌肉质量较低）的患者，基于血清肌酐水平的估计肾小球滤过率 (eGFR) 值会过高。我们还在一组接受肾恶性肿瘤手术的患者中测试了 SI 的预后价值。我们对 2017 年 4 月至 2023 年 6 月期间在国立癌症中心东医院（千叶县柏市）接受肾肿瘤手术的 322 名患者进行了一项回顾性观察性研究。我们评估了肌少症，测量腰肌指数 (PMI)、腰肌密度 (PMD) ）和骨骼肌面积（SMA）（通过计算机断层扫描）。我们评估了手术前后 SI 和 eGFR 之间的关联。我们还评估了 SI 与术后结果（包括总体生存率）之间的关联。 322 名患者中，211 名（66%）为男性，中位年龄为 69 岁。 SI 与男性的 PMI 和 PMD 均呈弱相关性（PMI：ρ = 0.25；PMD：ρ = 0.21）。在女性中，SI 和 PMD 表现出较低的相关性（ρ = 0.26），而 SI 和 PMI 表现出不显着的相关性（ρ = 0.19）。对于男性和女性来说，SMA 和 SI 之间的相关性均为中等（男性：ρ = 0.51；女性：ρ = 0.46）。根治性肾切除术后，高 SI 患者中 98% 的 eGFR 下降，而低 SI 患者中这一比例为 69%。我们还证明低 SI 预示着不良预后。临床医生可以通过测量手术前后的 SI 来认识到低 SI 组 eGFR 被高估的可能性。低 SI 也可能有助于预测不良预后。