In adults who are critically ill, levels of urine complement factor Ba (an activation fragment of factor B) reflect the presence and severity of acute kidney injury (AKI) as well as the likelihood of AKI recovery or persistence, according to a meta-analysis in Kidney International Reports.
The researchers analyzed data on 439 adults who were critically ill, drawn from a clinical trial of early erythropoietin therapy. Of these, 187 patients had AKI at the time of intensive care unit (ICU) admission (123 patients) or at 24 to 48 hours after (64 patients). The remaining 252 patients did not have AKI.
Urine Ba fragment levels were measured in samples collected at ICU admission and at 24 and 48 hours. Associations between urine Ba and patient outcomes were assessed, including the presence, persistence, and resolution of AKI. About one-half of patients had AKI recovery (serum creatinine reduction to <0.3 mg/dL above baseline) within 48 hours. The rest were classified as having persistent AKI.
Urine Ba levels rose with increasing AKI stage, after adjustment for age and critical illness severity (applying the APACHE II [acute physiology and chronic health evaluation II] score). Urine Ba was significantly higher in patients with persistent AKI versus recovery: odds ratio, 6.6 per doubling of urine Ba level.
Urine Ba effectively discriminated between patients with and without AKI. Higher urine Ba levels were also associated with worse organ failure outcomes, including reductions in days alive, ventilator-free days, inotrope-free days, and ICU-free days.
In adults who are critically ill, AKI is associated with high morbidity and mortality and has no specific treatment options. Previous reports have suggested that complement activation fragments might be useful biomarkers of AKI.
“Our findings add to previous preliminary evidence demonstrating the association between urine Ba and AKI severity,” the researchers write. The findings also suggest that higher urine Ba levels may be useful in identifying patients with AKI persistence or recovery. The authors discuss the implications for future studies of AKI treatment, including trials of factor B inhibition [Stenson EK, et al. Urine complement factor Ba identifies persistent acute kidney injury and organ failures in critically ill adults. Kidney Int Rep, published online November 24, 2024. https://doi.org/10.1016/j.ekir.2024.11.030].
