Utility of cytomegalovirus viral load in renal transplant patients in Argentina

Background. Cytomegalovirus (CMV) is the most prevalent viral disease in so lid organ transplantation. Detection of CMV DNA in peripheral blood mononuc lear cells (PBMC) by polymerase chain reaction (PCR) frequently occurs in r enal allograft recipients, yielding false positive results in seropositive patients free of CMV disease. We evaluated the clinical utility of a quanti tative PCR enzyme-linked immunosorbent assay (ELISA) for identifying patien ts with CMV disease. Methods. Three hundred and fifty samples from 65 consecutive renal transpla nt recipients were studied. DNA was extracted from PBMC weekly up to the da y of discharge and after any further admission. Samples were tested by a qu alitative PCR method, and all positive samples were further studied by a qu antitative PCR-ELISA method. The quantitative PCR-ELISA method used an inte rnal standard (IS) that contained the primer sequences used in the qualitat ive CMV PCR. Detection and quantification was performed in 96-well plates c oated with IS or CMV specific probes. Results. Forty-one of 65 patients (63.1%) showed positive results by the qu alitative PCR, but only 8 of these patients were diagnosed with CMV disease . Positive samples were re-analyzed by the quantitative assay. The 8 patien ts with CMV disease had a mean CMV viral load of 1,438+/-687 viral copies ( VC)/10(6) PBMC, and the 33 without CMV disease had a mean value of 219.6+/- 117.2 VC/10(6) PBMC (P<0.01). None of the 33 patients without CMV disease h ad viral loads higher than 500 VC/10(6) PBMC. Using 500 VC/10(6) PBMC as a cut-off value for CMV disease, the quantitative PCR showed a sensitivity an d specificity of 100% compare to clinical diagnosis. Conclusion. CMV viral load may be useful in the diagnosis of CMV disease in renal transplant patients.