Biomarkers of renal injury, basic overview, analytical difficulties of their determination and possible clinical significance
Abstract
Renal insufficiency is associated with numerous comorbidities and increased mortality. A distinction should be made between chronic kidney disease (CKD), acute kidney injury (AKI) and prerenal AKI.
Newer AKI markers could be used, especially neutrophil gelatinase-associated lipocalin (NgAL), cystatin C, N-acetyl-β-D-glucosaminidase (NAg), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), liver-type fatty acid-binding protein (L-FABP). The examination of them is recommended mostly in urine, the predictive value is probably higher in children.
Due to their lack of sensitivity and specificity, it is considered appropriate to investigate a combination of two of them. The most promising is considered the determination of urinary NgAL, resp. its monomeric form derived from renal epithelium.
Serum creatinine is the most frequently investigated nephrological marker, but its increase occurs relatively late. However, it still plays the most important role in the diagnosis of renal insufficiency in clinical practice, it is the basis for the estimation of glomerular filtration (gF).
Its determination, both by the Jaffe method and enzymatically, have to be linked to the indication of the gF value and to the reference system. when estimating gF from enzymatically determined creatinine, we have to take into account that this more accurate method provides higher values compared to the Jaffe method in the area of higher creatinine concentrations (> 250 μmol/L). This can have serious diagnostic consequences (leading to earlier start of dialysis), especially in pediatric patients, where the Schwartz formula for the enzymatical creatinine includes a uniform and lower factor F in addition.
Albuminuria is considered to be the most important marker of renal damage in CKD. Immunochemical methods do not capture so-called immuno-unreactive albumin.
Due to this, albuminuria is underestimated, especially in diabetics in the A1 area, despite the method's connection to the reference system.