Predictive ability of circulating osteoprotegerin as a novel biomarker for early detection of acute kidney injury induced by sepsis

Background: Though significant progress has been made towards new diagnostic approaches for early detection of acute kidney injury (AKI) induced by different factors, there is still an urgent demand for a more specific and predictive biomarker for each type. The aim of this study is to unravel the potential diagnostic utility of circulating osteoprotegerin (OPG) in septic patients who developed AKI in the ICU, compared to cystatin C (a renal function maker) and KIM-1 (a kidney damage marker). Methods: Eighty patients (male = 43, female = 37) with ages ranging from 42 to 46 years and with sepsis, 40 of whom developed AKI, and 30 healthy controls were enrolled in this prospective study. Results: Results revealed significant progressive elevation of OPG, along with cystatin C and KIM1, among sepsis, severe sepsis, and sepsis-AKI patients. The progression of OPG levels paralleled the deterioration of kidney and endothelial functions from sepsis to sepsis-AKI, revealed as progressively increased levels of serum Eselectin (15.3%), endothelin-1 (ET-1) (19.6%), and decreased nitric oxide (NO) (29.7%), associated with elevations of TNF-alpha (25.5%) and TGF-beta (18%). Their comparative prognostic validity of sepsis-AKI was assessed using ROC analysis, which revealed that OPG, KIM-1, and cystatin C showed similar AUCs (0.827-0.83) but with different sensitivities, viz., 84%, 88%, and 92%, respectively. Although cystatin showed 82% specificity, OPG showed a higher, similar specificity to KIM-1 of 85%, indicating its potential function as a marker of renal damage such as KIM-1. Conclusion: This study revealed a significant elevation of circulating OPG in septic patients with different levels of severity and those who progressed to AKI. Moreover, OPG showed a significant correlation to KIM-1 and cystatin, as well as conventional renal, inflammatory, and endothelial markers. Having a similar specificity to KIM-1, as evidenced by the ROC analysis, OPG has the potential to serve as a reliable biomarker of kidney damage in cases of sepsis-AKI.