Development and evaluation of a practical ELISA for human urinary lipocalin-type prostaglandin D synthase.

BACKGROUND: Urinary excretion of lipocalin-type prostaglandin D synthase (L-PGDS) is significantly increased in patients with chronic renal failure, but its diagnostic potential in less advanced stages of renal diseases remains to be elucidated.
METHODS: Six mouse monoclonal antibodies (MAbs) were raised against recombinant human L-PGDS. We constructed a sandwich ELISA with two MAbs that recognized different epitopes with high affinities and assessed its assay performance and clinical utility with urine samples from healthy controls, diabetic patients, and patients with various renal diseases.
RESULTS: Western blot analyses with NH(2)-terminus-truncated L-PGDS mapped the epitopes to Ala(23)-Val(28) (MAb-7F5 and -10A3), Ser(52)-Ala(73) (MAb-9A6), Tyr(107)-Val(120) (MAb-1B7 and -6F5), and Gly(140)-Pro(155) (MAb-6B9). A sandwich ELISA was constructed with MAb-1B7 and -7F5, the K(d) values of which were 3.6 and 3.9 nmol/L, respectively, for native L-PGDS. Recoveries were 91-111%, and intra- and interassay CVs were <6% and <9%, respectively. The ELISA showed parallelism of standard and urine samples and no significant interference by a variety of urinary constituents. Urinary L-PGDS excretion was significantly increased in patients with diabetic nephropathy, IgA nephropathy, and chronic glomerulonephritis even when serum creatinine was not increased. In patients with renal diseases, urinary L-PGDS was correlated with urinary albumin (r = 0.64; P <0.0001), N-acetyl-beta-D-glucosaminidase (r = 0.43; P <0.001), and serum creatinine (r = 0.66; P <0.0001). At a cutoff value of 284 mg/mol creatinine, the assay had sensitivities of 74% for diabetic nephropathy and 83% for chronic glomerulonephritis and a specificity of 93%.
CONCLUSIONS: This ELISA system is suitable for measurement of urinary L-PGDS in a routine clinical assay and may be useful to detect less advanced stages of renal diseases.