目的 探讨重症肺炎患儿血清25-羟基维生素D[25（OH）D]水平动态变化与患儿病情危重程度变化及实验室相关检测指标间的相关性。方法 选取2017年3月至2018年3月重症肺炎住院患儿132例为重症肺炎组，按照入院时和治疗1周后患儿的危重程度将重症肺炎患儿分为非危重组、危重组和极危重组，患儿例数在入院时分别为41例、59例及32例，治疗1周后则分别为78例、35例及19例；另选取同时期142例行健康体检合格的婴幼儿作为健康对照组。检测患儿入院时和治疗1周后血清25（OH）D、降钙素原（PCT）及N末端钠尿肽原（NT-proBNP）水平，以及健康对照组入院时血清25（OH）D水平，根据治疗1周后25（OH）D的变化将重症肺炎患儿分为维生素D（VD）升高组（n=81）和VD下降组（n=51）。对检测指标进行比较分析及相关性分析。结果 重症肺炎患儿血清25（OH）D水平明显低于健康对照组（P < 0.05）。健康对照组血清25（OH）D水平明显高于不同危重程度组（P < 0.05）；入院时及治疗1周后非危重组25（OH）D水平均明显高于危重组和极危重组（P < 0.01），危重组25（OH）D水平明显高于极危重组（P < 0.05）；不同时间点各亚组间PCT和NT-proBNP水平比较差异均有统计学意义（P < 0.01），极危重组和危重组PCT和NT-proBNP水平均明显高于非危重组（P < 0.05）。治疗1周后VD升高组患儿病情的危重程度要低于VD下降组；VD升高组出院结局好于VD下降组（P < 0.01）。重症肺炎患儿血清25（OH）D水平治疗前后变化差值与PCT、NT-proBNP水平治疗前后变化差值均呈显著负相关（分别r=-0.597、-0.404，P < 0.01）。结论 VD水平变化与婴幼儿重症肺炎病情危重程度变化相关，可作为病情监测的指标，补充VD可能有助于疾病的康复。

Objective To study the correlation of dynamic change in serum 25-hydroxy vitamin D[25(OH)D] level with the disease severity and related laboratory markers in infants/toddlers with severe pneumonia. Methods A total of 132 infants/toddlers with severe pneumonia who were hospitalized between March 2017 and March 2018 were enrolled as the severe pneumonia group. According to the disease severity on admission and after one week of treatment, they were further divided into non-critical group (41 children on admission and 78 after one week of treatment), critical group (59 children on admission and 35 after one week of treatment), and extremely critical group (32 children on admission and 19 after one week of treatment). A total of 142 infants/toddlers who underwent physical examination during the same period of time were enrolled as the healthy control group. The serum levels of 25(OH)D, procalcitonin (PCT), and N-terminal pro-brain natriuretic peptide (NT-proBNP) were measured on admission and after one week of treatment for the severe pneumonia group, and the serum level of 25(OH)D was measured on admission for the healthy control group. According to the 25(OH)D level after one week of treatment, the children with severe pneumonia were divided into increased vitamin D (VD) group with 81 children and reduced VD group with 51 children, and a comparative analysis and a correlation analysis were performed. Results The severe pneumonia group had a significantly lower mean 25(OH)D level than the healthy control group (P < 0.05), and all the three subgroups of different severities had significantly lower 25(OH)D level than the healthy control group (P < 0.05). On admission and after one week of treatment, the non-critical group had a significantly higher 25(OH)D level than the critical and extremely critical groups (P < 0.01), and the critical group had a significantly higher 25(OH)D level than the extremely critical group (P < 0.05). The extremely critical and critical groups had significantly higher serum levels of PCT and NT-proBNP than the non-critical group on admission and after one week of treatment (P < 0.05). After one week of treatment, compared with the reduced VD group, the increased VD group had a significantly less serious condition. At discharge, the increased VD group had a significantly better outcome compared with the reduced VD group (P < 0.01). In the children with severe pneumonia, the change value of serum 25(OH)D level after treatment was negatively correlated with the change values of PCT and NT-proBNP (r=-0.597 and -0.404 respectively; P < 0.01). Conclusions The change in VD level is correlated with the severity of severe pneumonia in infants/toddlers and can be used as an index for disease monitoring. VD supplementation may help with disease recovery.