# Exploring the Value of sC5b‐9 in the Diagnosis of Haematopoietic Stem Cell Transplant‐Associated Thrombotic Microangiopathy in Children

## TL;DR

This study finds that elevated sC5b-9 levels after stem cell transplants in children can help predict and diagnose a serious condition called TA-TMA.

## Contribution

The study identifies a specific sC5b-9 threshold (306.4 ng/mL) for diagnosing TA-TMA after stem cell transplants in children.

## Key findings

- sC5b-9 levels are significantly elevated during TA-TMA in children post-transplant.
- A cut-off of 306.4 ng/mL for sC5b-9 has 90.5% sensitivity and 86.6% specificity for TA-TMA diagnosis.
- TA-TMA patients had a significantly lower 1-year survival rate compared to non-TA-TMA patients.

## Abstract

This study aims to explore the association between plasma human terminal complement complex C5b‐9 (sC5b‐9) levels and the occurrence of haematopoietic stem cell transplantation‐associated thrombotic microangiopathy (TA‐TMA) in children. The study retrospectively analysed the data of 131 patients who underwent allogeneic haematopoietic stem cell transplantation (allo‐HSCT) at the Department of Haematology‐Oncology between May 2020 and July 2023. The clinical data included dynamic data on plasma sC5b‐9 concentrations and analysed the potential of pre‐ and post‐transplantation levels for the prediction and diagnosis of TA‐TMA after allo‐HSCT. The median age of the cohort was 5.9 [3.4, 10.8] years, and it comprised 73 (55.8%) male and 58 (44.2%) female patients. The primary diseases were haematologic malignancy in 57 cases (43.5%), aplastic anaemia in 39 cases (29.8%) and Mediterranean anaemia in 13 cases (9.9%). Out of the 131 patients, 21 (14.7%) developed TA‐TMA, and the median time of onset was 88 [59, 136] days after transplantation. The 1‐year overall survival rate was significantly higher in the non‐TA‐TMA group (92.7% ± 2.5%) than in the TA‐TMA group (47.6% ± 10.7%) (χ2 = 35.71, p < 0.05). During TA‐TMA, sC5‐9 levels are significantly elevated (p < 0.05). However, the baseline levels of sC5b‐9 before allo‐HSCT were not related to the development of TA‐TMA after the procedure. The plasma sC5b‐9 concentration after allo‐HSCT in children is closely related to the occurrence of TA‐TMA, and 306.4 ng/mL is an optimal clinical cut‐off level above which TA‐TMA is indicated. This cut‐off level was associated with a sensitivity of 90.5% and a specificity of 86.6%. Nonetheless, the diagnosis of TA‐TMA should be established in conjunction with clinical manifestations and corroborated by additional laboratory test results.