The emerging role of biomarkers in diabetic and hypertensive chronic kidney disease.

Currently used measures to assess kidney function and injury are largely inadequate. Markers such as serum creatinine, formulas to estimate glomerular filtration rate, cystatin C, and proteinuria largely identify an underlying disease process that is well established. Thus, there has been a recent effort to identify new biomarkers that reflect kidney function, early injury, and/or repair that ultimately can relate to progression or regression of damage. Several biomarkers emerged recently that are able to detect kidney damage earlier than is currently possible with traditional biomarkers such as serum creatinine and proteinuria. Identification of urine biomarkers has proven to be beneficial in recent years because of ease of handling, stability, and the ability to standardize the various markers to creatinine or other peptides generally already present in the urine. Recent markers such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and podocin have garnered a lot of attention. The emergence of these and other biomarkers is largely because of the evolution of novel genomic and proteomic applications in investigations of acute kidney injury and chronic kidney disease. In this article, we focus on the applications of these biomarkers in disease.

Validation of human haptoglobin immunoturbidimetric assay for detection of haptoglobin in equine and canine serum and plasma.

The Incstar(R) SPQ II human haptoglobin (Hpt) (Incstar Corporation, Stillwater, MN) immunoturbidimetric assay was validated for the determination of serum and plasma Hpt concentrations in dogs and horses. The anti-human Hpt antiserum supplied with the assay, displayed monospecificity to both dog and horse serum Hpt by immunoelectrophoresis and Western blotting techniques. The automated immunoturbidimetric assay results correlated well with the cyanmethemoglobin binding assay (r=0.953 for canine serum and r=0.941 for equine serum), and had excellent precision at both high and low serum Hpt concentrations (within run and between run coefficients of variation near or less than 5%). The assay was linear in both species by serial dilution of pooled-high serum with pooled-low serum, saline and with Hpt-free serum. Interference from hemolysis (> 25 mg/dl hemoglobin) and lipemia greater than 100 mg/dl caused a false decrease and false increase respectively in Hpt yield with the immunoturbidimetric assay. The anti-Hpt antibody supplied with the assay kit, once diluted with polymer diluent and stored at 4 degrees C, was stable for up to 6 days and gave consistent results.