Neopterin as a new marker to detect acute rejection after heart transplantation.

Neopterin is excreted at high levels in the course of activation of the immunologic system during allograft rejection or viral infection. This pteridine therefore may be considered as a specific indicator of T cell-mediated immunity. With radioimmunoassay we analyzed both serum and urine levels of neopterin in 43 patients after orthotopic heart transplantation. These data were correlated to the histologic finding at routine endomyocardial biopsies (EMB). In case of rejection (that is, grades I to II or more in EMB) serum levels of neopterin increased about 156% +/- 94% within 1 week before EMB, whereas urine levels increased about 215% +/- 137%. The most marked increase was seen 2.8 days before the corresponding EMB. The predictive value theory was used to elaborate the reliability of the correlation between an increase of neopterin levels and the occurrence of an acute rejection episode. With regard to serum levels, sensitivity and specificity were 0.872 and 0.815, respectively. The positive predictive value was 0.41 and the negative predictive value was 0.977. We found similar results in urine levels.