Fibrinogen (FIB) is often elevated in children with Henoch Schonlein purpuric nephritis (HSPN), but the correlation between FIB and renal lesions has been less studied.

To explore the correlation between FIB in children with HSPN and the International Study Group on Pediatric Kidney Disease (ISKDC) pathology grading and micropathological changes in parts of renal units, and to clarify whether FIB can assess the severity of renal injury in children with HSPN.

In total, 922 children with HSPN who were hospitalized in the First Affiliated Hospital of Henan University of Chinese Medicine in the pediatric nephrology ward and underwent kidney biopsy at the same time from December 2017 to December 2022 were collected, and the clinical information, FIB and renal pathological information during renal biopsy were summarized, and based on the FIB level, the children were categorized into group A (low) <2.38 g/L, group B (standard) 2.38-4.98 g/L, and group C (high) >4.98 g/L. The correlation between FIB and ISKDC pathological grades, glomerular mesangial hyperplasia ratio, the crescentic bodies ratio and the nature of the glomerular lesions from acute to chronic was investigated by Spearman rank correlation analysis, and the prediction of FIB on the micropathological changes of renal units was analyzed by the subject's work characteristic (ROC) curve.

Among 922 children with HSPN who had undergone renal biopsy, the FIB was (3.48±1.01) g/L. 113 cases in group A had a low FIB rate of 12.26%; 734 cases in group B had a standardized FIB rate of 79.61%; and 75 cases in group C had a high FIB rate of 8.13%. The ISKDC pathology classification was type Ⅱa in 173 cases (18.76%), type Ⅱb in 29 cases (3.15%), 466 cases (50.54%) of type Ⅲa, 232 cases (25.16%) of type Ⅲb, and 22 cases (2.39%) of type Ⅳ and above (including 2 cases of type Ⅳa, 18 cases of type Ⅳb, and 2 cases of type Ⅴ). The results of the Spearman's rank correlation analysis showed that the FIB and the grouping of the FIB of the children with HSPN were positively related to the renal pathology ISKDC grading (r_s=0.146, P<0.001; r_s=0.129, P<0.001). 911 (98.80%) of 922 children with HSPN were mesangial proliferative, and 655 (71.04%) had crescentic hyperplasia. Spearman rank correlation analysis showed a weak positive correlation between FIB and FIB subgroups and the rate of mesangial hyperplasia (r_s=0.092, P=0.005; r_s=0.096, P=0.003), and a positive correlation with the rate of crescentic bodies (r_s=0.132, P<0.001; r_s=0.830, P=0.012). 922 children with HSPN had glomerular acute lesions in 763 cases (82.75%), acute chronic lesions in 97 cases (10.52%), and chronic lesions in 62 cases (6.73%). In addition, FIB gradually increased with the nature of the glomerular lesions from acute to chronic (r_s=0.145, P<0.001). At the same time, comparison of some renal biopsy indexes FIB in HSPN children showed statistically significant difference (P<0.05). The ROC curves showed that the FIB had the highest sensitivity for glomerulosclerosis (sensitivity=0.900, specificity=0.303), and the optimal cutoff value for FIB was 2.835 mg/L; the area under the ROC curve (AUC) of FIB for the positive prediction of tubulointerstitial fibrosis=0.623, and that of FIB for the reverse prediction of tubulointerstitial cellular granulomatous degeneration=0.641.

FIB can be used as a laboratory index reflecting the severity of renal pathological changes in patients with HSPN, can reflect the severity of renal pathological grading, is closely related to irreversible lesions according to renal microscopic indicators such as glomerular sclerosis and balloon adhesion, and can assist clinical diagnosis and treatment.

临床中紫癜性肾炎（HSPN）患儿多存在纤维蛋白原（FIB）升高现象，但FIB与肾脏病变相关性的研究较少。

探讨HSPN患儿FIB与国际小儿肾脏病研究组（ISKDC）病理分级及肾单位部分微观病理变化的相关性，明确FIB能否评估HSPN患儿肾损伤轻重。

收集2017年12月—2022年12月在河南中医药大学第一附属医院儿科医院肾病病区住院同时行肾活检的HSPN患儿922例，汇总其做肾活检期间的临床信息、FIB及肾脏病理信息，并依据FIB水平将患儿分为A组（偏低）<2.38 g/L、B组（标准）2.38~4.98 g/L、C组（偏高）>4.98 g/L。采用Spearman秩相关分析探究FIB与ISKDC病理分级、肾小球系膜增生比例、新月体增生比例及肾小球急慢性病变情况的相关性；再通过受试者工作特征（ROC）曲线分析FIB对肾单位微观病理变化的预测情况。

922例已做肾活检的HSPN患儿中，FIB为（3.48±1.01）g/L。A组113例，FIB偏低率占12.26%；B组734例，FIB标准率占79.61%；C组75例，FIB偏高率占8.13%。ISKDC病理分级中Ⅱa型173例（18.76%）、Ⅱb型29例（3.15%）、Ⅲa型466例（50.54%）、Ⅲb型232例（25.16%）、Ⅳ型及以上22例（2.39%）（其中Ⅳa型2例，Ⅳb型18例，Ⅴ型2例）。Spearman秩相关分析结果显示，HSPN患儿FIB及FIB分组与肾脏病理ISKDC分级（r_s=0.146，P<0.001；r_s=0.129，P<0.001）呈正相关性。922例HSPN患儿中有911例（98.80%）存在系膜细胞增生，655例（71.04%）存在新月体增生。Spearman秩相关分析结果显示，FIB、FIB分组均与系膜细胞增生率呈弱正相关性（r_s=0.092，P=0.005；r_s=0.096，P=0.003），与新月体增生率呈正相关性（r_s=0.132，P<0.001；r_s=0.830，P=0.012）。922例HSPN患儿中肾小球急性病变763例（82.75%）、急慢性病变97例（10.52%）、慢性病变62例（6.73%）。HSPN患儿FIB与肾小球病变的急慢性情况呈正相关（r_s=0.145，P<0.001）。同时，HSPN患儿部分肾活检指标FIB比较，差异有统计学意义（P<0.05）。ROC曲线显示，FIB对肾小球硬化的灵敏度最高（灵敏度=0.900，特异度=0.303），FIB最佳截断值为2.835 mg/L；FIB对小管间质纤维化正向预测的ROC曲线下面积（AUC）=0.623，对小管细胞颗粒变性反向预测的AUC=0.641。

FIB可作为一项反映HSPN患儿肾脏病理变化轻重的实验室检查指标，能反映肾脏病理分级的轻重，与肾小球硬化、球囊粘连等肾单位微观指标关系密切，可协助临床诊断和治疗。