Myeloperoxidase as serum marker for detection of CMV infections and rejections in patients after liver or heart transplantation.

Rejection episodes and infections are common problems after organ transplantations (TX). Rejection can be diagnosed in liver-transplant (LTX) patients when liver-specific enzymes in the serum are elevated. As endomyocardial biopsy (EMB) is the gold standard for detecting heart transplant (HTX) rejection, serum parameters would permit more selective use of this invasive procedure. Cytomegalovirus (CMV) infections can have serious consequences for TX patients and so should be diagnosed and treated timely. At present, there are no suitable diagnostic methods other than CMV antigen pp65 and CMV polymerase chain reaction (PCR). Our study aimed to test the sensitivity of myeloperoxidase (MPO), an enzyme of neutrophilic granulocytes, as a new serum parameter in addition to established serum parameters and EMB for diagnosis of infection and rejection episodes after LTX and HTX. MPO in plasma from 246 blood samples (103 used for statistical analysis) from 27 patients (18 LTX and 9 HTX) was determined using ELISA; C-reactive protein (CRP), gamma-glutamyl-transpeptidase (GGT), white blood count and CMV pp65 antigen were monitored routinely. EMBs were performed at defined intervals after HTX. Results were analyzed with descriptive statistics, T-test, Wilcoxon test and Cox regression analysis, whereby a p<0.05 was viewed as significant. MPO values in TX patients with an infection (7 LTX, 2 HTX) were significantly higher than in TX patients without complications (control group) (253.9 microg/l vs. 116.6 microg/l, p=0.0194). In TX patients with rejections (6 LTX, 6 HTX), there is also a significant increase in comparison to controls (429.7 microg/l vs. 116.6 microg/l, p=0.0001). Data from individual TX patients, however, indicate that MPO levels rise distinctly earlier with infection (CMV) than with rejection, enabling earlier detection of the complication and initiation of suitable treatment. Our findings suggest that a larger and prospective study should be designed to evaluate the usefulness of MPO levels in assessing organ transplant recipients.