Diagnostic value of serum proenkephalin as a biomarker of renal dysfunction in Iraqi patients with chronic kidney disease

Abstract

Objective: To evaluate serum proenkephalin (PENK) levels in Iraqi patients with chronic kidney disease (CKD) and examine its diagnostic performance and correlation with conventional renal function markers. Methods: This case-control study included 45 Iraqi patients with CKD stages 3–4 and 45 age- and sex-matched healthy controls. Serum PENK levels were measured using a commercial ELISA kit. Renal function was assessed using serum creatinine, blood urea, and estimated glomerular filtration rate (eGFR) calculated with the CKD-EPI equation. Results: Serum PENK levels were significantly higher in CKD patients (900.05 ± 212.72 ng/L) than in controls (705.12 ± 135.95 ng/L; p < 0.001). PENK positively correlated with creatinine (r = 0.678, p < 0.001) and urea (r = 0.579, p < 0.001) and negatively with eGFR (r = –0.486, p < 0.001). Concentrations rose markedly from stage 3 (717.65 ± 134.74 ng/L) to stage 4 (1124.14 ± 295.63 ng/L; p < 0.001). Receiver operating characteristic analysis yielded an area under the curve of 0.723 (p = 0.001), with 65% sensitivity and 60% specificity at a cut-off of 728.7 ng/L. Conclusion: Serum PENK is significantly elevated in Iraqi patients with moderate-to-advanced CKD and correlates with disease severity. However, its modest diagnostic accuracy and inability to distinguish early-stage 3 disease from healthy controls suggest that PENK is best used as an adjunctive marker rather than a standalone screening test.