Neopterin--its clinical use in urinalysis.

Increased amounts of neopterin are released during cellular immune response. Neopterin concentrations can be monitored in serum and urine of patients since neopterin is removed from the circulation by renal excretion. In allograft recipients, rising neopterin concentrations indicate rejection episodes early. Neopterin concentrations correlate with the extent and activity of viral infections, malignancies, and autoimmune diseases. We investigated excretion kinetics of neopterin in a rhesus monkey which received a high dose of neopterin intravenously. A sharp increase of urinary neopterin concentrations was observed, and from the data the half-life of neopterin in the circulation was estimated to be 90 minutes. By comparing urine and serum neopterin concentrations in HIV seropositive and seronegative human individuals, a strong correlation and similar diagnostic sensitivity between urine and serum values was observed. Thus, neopterin concentrations in serum or urine seem of equal value for diagnostic application as long as renal function is normal.