An assay for quantitation of cytomegalovirus (CMV) has been developed. The assay combines DNA amplification and enzyme-linked immunosorbent assay (ELISA) detection. In this study, the assay has been used to examine sequential buffycoats from 32 consecutive liver transplant recipients. In a febrile patient, CMV titres in excess of lo4 copies per 150,000 cells strongly suggest a diagnosis of symptomatic CMV infection. Antiviral therapy causes a rapid decline in viral titre. Viral titres are seen to rise presymptomatically in nfection with cytomegalovims (CMV) remains an I important cause of morbidity in immunosuppressed transplant recipients. The association of symptomatic infection with virus isolation from buQ-coat is well e~tab1ished.l.~ Recently, the polymerase chain reaction (PCR) has been proposed as a potentially useful test for the detection of CMV in this ~e t t i n g .~. '~ Assay sensitivity depends on (1) method of substrate preparation, (2) primer design, (33 thermal cycling conditions, and (4) post-PCR detection method. When performance of the assay is optimized, CMV can be detected in blood of immunocompetent blood donor^.'^,'^ Such a sensitive assay would not provide useful information for the management of immunosuppressed patients. Most investigators agree that PCR has excellent sensitivity and negative predictive value (for the diagnosis of symptomatic infection), but that specificity and positive predictive value are poor. Discordant conclusions concerning the clinical utility of PCR detection may result from differences in assay DNA detection sensitivity, which in turn result from interlaboratory methodological differences.For any given substrate and conditions, the efficiency of the PCR reaction varies. Problems of interpretation arising from interassay and interlaboratory variation in PCR efficiency might be overcome by the inclusion of an internal standard DNA sequence in each r e a c t i~n . '~.~~ We have developed a quantitative assay for CMV detection that combines a single PCR reaction with enzyme-linked immunosorbent assay (ELISA) detection.Sequential bu&-coats Materials and MethodsThirtytwo consecutive liver transplant recipients were studied for 3 months after transplantation. Prospective virologcal surveillance was not performed. Sera were examined retrospectively for CMV immunoglobulin (19, M, and for the purposes of this report CMV infection is defined by the presence of CMV IgM. Symptomatic CMV infection ("CMV disease") is defined by the following criteria. Fever (>38"C on at least 2 consecutive days) and serum IgM positivity, with either leukopenia (count < 3 x 10y/l), and/or histological evidence of invasive infection.Patients did not receive antiviral prophylaxis. When symptomatic CMV infection was diagnosed, treatment included reduction of immunosuppression and administration of ganciclovir ( I 0 mg/kg/d adjusted for renal dysfunction).Blood was sampled weekly during the inpatient stay, and then at each outpatient attendance for 3 months. Serum was separated from clotted bloo...