1. Diagnostic Tests for Cytomegalovirus in Renal Transplantation

Serology should be used pretransplant to define cytomegalovirus (CMV) serological status and thereby stratify the risk of CMV infection post-transplant. • Quantification of viral load may enable the prediction of likelihood of progression to disease based on absolute value and the rate of rise of viral load. Hence, a pp65 antigenaemia or a quantitative DNA test is preferred over a qualitative DNA test. The threshold levels for various tests at which to initiate pre-emptive therapy have not been critically defined in renal transplant and depend on the particular assay used. • There is marked variability in CMV DNA levels between different PCR assays. • There is high inter-laboratory variability in CMV DNA levels. • Some CMV PCR assays are unable to detect CMV at low viral loads. • If treatment for CMV does not result in clinical improvement and a reduction in viral load, testing for ganciclovir resistance is recommended. • Optimal cut-offs for both antigenaemia and quantitative PCR testing have been proposed; however, this is dependent on each laboratory and there is no consistency between different test assays. If pre-emptive treatment is to be used: • Patients at risk of CMV infection should be monitored for evidence of infection by a validated and preferably standardized detection method. In practical terms, this currently means either the pp65 antigenaemia assay or a quantitative nucleic acid assay. • Monitoring of patients not receiving prophylaxis should be regular, but there is no evidence to guide the frequency of testing based on outcome data or cost-effectiveness. Less than fortnightly testing is unlikely to be effective for preemptive treatment strategies. Nephrology 16 (2011) 683–687