Hypophosphatemia is an independent risk factor for AKI among hospitalized patients with COVID-19 infection

This study sought to investigate incidence and risk factors for acute kidney injury (AKI) in hospitalized COVID-19. In this retrospective study, we enrolled 823 COVID-19 patients with at least two evaluations of renal function during hospitalization from four hospitals in Wuhan, China between February 2020 and April 2020. Clinical and laboratory parameters at the time of admission and follow-up data were recorded. Systemic renal tubular dysfunction was evaluated <i>via</i> 24-h urine collections in a subgroup of 55 patients. In total, 823 patients were enrolled (50.5% male) with a mean age of 60.9 ± 14.9 years. AKI occurred in 38 (40.9%) ICU cases but only 6 (0.8%) non-ICU cases. Using forward stepwise Cox regression analysis, we found eight independent risk factors for AKI including decreased platelet level, lower albumin level, lower phosphorus level, higher level of lactate dehydrogenase (LDH), procalcitonin, C-reactive protein (CRP), urea, and prothrombin time (PT) on admission. For every 0.1 mmol/L decreases in serum phosphorus level, patients had a 1.34-fold (95% CI 1.14–1.58) increased risk of AKI. Patients with hypophosphatemia were likely to be older and with lower lymphocyte count, lower serum albumin level, lower uric acid, higher LDH, and higher CRP. Furthermore, serum phosphorus level was positively correlated with phosphate tubular maximum per volume of filtrate (TmP/GFR) (Pearson <i>r</i> = 0.66, <i>p</i> &lt; .001) in subgroup analysis, indicating renal phosphate loss <i>via</i> proximal renal tubular dysfunction. The AKI incidence was very low in non-ICU patients as compared to ICU patients. Hypophosphatemia is an independent risk factor for AKI in patients hospitalized for COVID-19 infection.

本研究旨在探讨住院新型冠状病毒肺炎（COVID-19）患者急性肾损伤（acute kidney injury, AKI）的发病率及危险因素。本项回顾性研究纳入了2020年2月至2020年4月期间，来自中国武汉4家医院的823例住院COVID-19患者，所有患者住院期间至少完成2次肾功能评估。研究记录了患者入院时的临床与实验室指标，并收集随访数据。对由55例患者组成的亚组，通过24小时尿液收集评估全身性肾小管功能障碍。本研究共纳入823例患者，其中男性占比50.5%，平均年龄为60.9±14.9岁。ICU患者中AKI发生率为38例（40.9%），而非ICU患者仅为6例（0.8%）。通过向前逐步Cox回归分析，我们识别出8项AKI独立危险因素：入院时血小板水平降低、白蛋白水平降低、血磷水平降低，以及乳酸脱氢酶（lactate dehydrogenase, LDH）、降钙素原、C反应蛋白（C-reactive protein, CRP）、尿素与凝血酶原时间（prothrombin time, PT）升高。血磷水平每降低0.1mmol/L，患者发生AKI的风险增加1.34倍（95%置信区间：1.14~1.58）。低磷血症患者往往年龄更大，淋巴细胞计数、血清白蛋白、尿酸水平更低，而LDH与CRP水平更高。亚组分析显示，血磷水平与每滤液容积的磷酸盐肾小管最大转运量（TmP/GFR）呈正相关（Pearson相关系数r=0.66，P<0.001），提示肾脏磷酸盐丢失是通过近端肾小管功能障碍实现的。与ICU患者相比，非ICU患者的AKI发生率极低。低磷血症是住院COVID-19患者发生AKI的独立危险因素。