PB0794 - Classification of Japanese patients with aHUS treated with eculizumab by a diagnostic scoring system

Background: Atypical hemolytic uremic syndrome (aHUS) is generally diagnosed by exclusion from other disorders of thrombotic microangiopathy (TMA) requiring considerable knowledge, and experience. Currently there are no definitive diagnostic makers available in clinical practice. Recently, a ‘TMA scoring system’ was developed along with an associated ‘aHUS score’ as a diagnostic tool (Wada et al. 2020).

Aims: We modified this system according to the variables recorded during a Japanese post-marketing surveillance (PMS) study and assessed the usefulness of the modified aHUS score using PMS data.

Methods: In PMS, 188 Japanese patients who were clinically diagnosed with aHUS and treated with eculizumab from 2013 to 2018 were registered. The treatment response was evaluated using 3 criteria: Criterion 1, partial hematologic response or renal improvement; Criterion 2, complete hematologic response or renal improvement; and Criterion 3, complete hematologic response and renal improvement. The relationship between the modified aHUS score and treatment response was investigated.

Results: A modified aHUS score value of 5 corresponded to the cutoff value from the previous report; 98% of patients met ≥5 points. In patients who had medical record after eculizumab treatment, 96% of patients fulfilled Criterion 1, 83% of patients fulfilled Criterion 2, and 30% of patients fulfilled Criterion 3. Higher percentages of patients with impaired renal function, younger onset and no underlying diseases were observed in the population who fulfilled Criterion 3. From Receiver Operating Characteristic curve analysis, the estimated cutoff value of modified aHUS score was approximately 10. In contrast, the odds ratio was highest at 5 points and 96% of patients with ≥5 points met the Criterion 1.

Conclusion(s): Almost all patients in PMS were classified as aHUS by modified aHUS score, which can be developed as a tool for predicting the response to eculizumab treatment in patients with aHUS.