The diagnostic capacity of serum amyloid A protein for early recognition of kidney allograft rejection.

We used new micro-ELISA test with sequence-specific antibody for every day monitoring of serum amyloid A protein (SAA) in 20 patients with kidney allografts in order to facilitate an early diagnosis of rejection. Altogether 44 SAA peaks were observed (beside those caused by surgery) and 22 of them were caused by allograft rejections. When allograft rejection occurred in postsurgical period (first 4 days), SAA levels rose to mean 706 +/- 161 mg/l while initial SAA peaks (caused by surgical trauma) reached the mean value 306 +/- 55 mg/l. The statistical significance was very high, P < 0.0001. In all nine rejection episodes in this period SAA peaks were higher than 400 mg/l, so we chose this level as a reference limit for this period. SAA peaks caused by allograft rejection in later period were also markedly higher (mean 461 +/- 176 mg/l) than those caused by infections or other complications (mean 133 +/- 82 mg/l, P < 0.001). Baseline mean level was 9 +/- 5 mg/l. In all 13 rejection episodes in this period SAA peaks were higher than 200 mg/l, so we chose this level as a reference limit for this period. In 20 of 22 rejection episodes (91%) SAA elevation predicted rejection and usually started to rise sharply 2 days before it. An excellent correlation between kidney allograft rejection and SAA reaction was found in this study (better than with CRP reaction) so we recommend everyday monitoring of SAA concentrations in patients with kidney allograft as a valuable aid in the early diagnosis and prediction of acute allograft rejection.