SERUM C-REACTIVE PROTEIN IS RARELY LOST INTO URINE IN PATIENTS WITH SECONDARY AMYLOIDOSIS AND PROTEINURIA

We studied whether the low serum C-reactive protein (S-CRP) level in p atients with inflammatory arthritis and proteinuria was due to the los s of CRP into urine. In 19 patients with secondary amyloidosis (14 wit h rheumatoid arthritis and five with juvenile chronic arthritis), S-CR P was measured with both immunoturbidimetric and radioimmunoassays. Th e concentration of urinary CRP was measured with a double-antibody rad ioimmunoassay. One patient with the most extensive proteinuria (12 g/2 4 h) excreted CRP at 14 mg/24 h, while in 18 of 19 patients only negli gible, if any, amounts of CRP were found in 24-h urine samples. Protei nuria of <8 g/24 h did not reduce the S-CRP level. Proteinuria exceedi ng this level may result in increased excretion of CRP into urine and consequently may result in a reduced S-CRP level.