Urinary 3-hydroxyproline excretion in Alport's syndrome: a non-invasive screening test?

Alport's syndrome is characterised by morphological and structural changes of the renal basement membranes. As the hydroxyproline content of isolated glomerular basement membranes is reduced in patients with Alport's syndrome, it is possible that the renal excretion of 3-hydroxproline (3-OHP), a key substrate of basement membrane collagen, may be altered in such patients. The urinary excretion of 3-OHP was determined by thin layer chromatography in 20 patients with Alport's syndrome, in healthy control subjects, and in patients with other renal diseases. These included patients with poststreptococcal glomerulonephritis, lower urinary tract infection, severe reflux nephropathy, lithium induced nephropathy, polycystic kidney disease, familiar benign haematuria, and renal graft rejection. Urinary excretion of 3-OHP was significantly higher in patients with Alport's syndrome compared with the patients with other renal diseases and the healthy control subjects. All other renal diseases investigated had 3-OHP values within the normal range. Urinary 3-OHP determination detected patients with Alport's syndrome with a high sensitivity (95.2%) and specificity (97.2%). We therefore suggest using urinary 3-OHP determinations as a simple non-invasive screening test for Alport's syndrome.