β-Trace Protein in Serum: A New Marker of Glomerular Filtration Rate in the Creatinine-Blind Range

Abstract

Recent studies have shown that low-molecular weight proteins in serum seem to be better markers for detecting reduced glomerular filtration rate (GFR) than the conventional measurement of serum creatinine (1)(2). Several proteins, such as ribonuclease, α₁-microglobulin, β₂-microglobulin (B2M), and cystatin C have been compared with serum creatinine (2)(3). Whereas serum creatinine is increased only after a reduction of ∼50% in GFR, the above proteins, especially cystatin C, are already increased within that so-called creatinine-blind range (1)(4)(5)(6). Recently, another low-molecular weight protein, the β-trace protein (BTP), isolated primarily from cerebrospinal fluid (7), was shown to be increased in patients with renal diseases (8)(9). However, there is no information on the relationship of BTP and a standard measure of GFR such as inulin clearance. Therefore, to investigate the potential clinical usefulness of BTP for early detection of reduced GFR, we have performed corresponding measurements of BTP and inulin clearance.