Determination of the urinary D/L trans-3-hydroxyproline ratio: a noninvasive screening test for Alport syndrome.

Because disturbed conformation of connective tissue proteins can be accompanied by increased racemization (i.e., an increased ratio of dextrorotatory (D) to levorotatory (L) amino acid molecules), we studied by high-performance liquid chromatography the renal excretion of the D-form of the basement membrane-specific trans-3-hydroxyproline in patients with Alport syndrome. The D/L ratio was significantly higher in patients with Alport syndrome than in patients with other renal diseases or in healthy control subjects. We therefore suggest that this factor may be a simple noninvasive (screening) test for Alport syndrome.