A lung transplant patient is diagnosed with cytomegalovirus (CMV) infection. What tests can be used to make the diagnosis? What therapy would you use to treat the disease, and how would you monitor the patient in order to decide when to stop treatment?
Risk factors for CMV include: CMV mismatch (donor is serologically CMV-positive and recipient is CMV-negative); use of lymphocyte-depleting therapy; and absence of antiviral prophylaxis in patients at risk.
The most common manifestation of CMV disease is a viremic syndrome, with fever, fatigue and myalgias; CMV can also cause tissue-invasive disease, such as hepatitis with transaminitis; esophagitis; colitis; leukopenia; and pneumonitis.
The two most common tests used to diagnose CMV infection are pp65 antigenemia and CMV viral load measured in peripheral blood by PCR. CMV antigenemia has been considered the gold standard for detection of CMV disease. However, it requires laboratory expertise and fresh blood samples. Viral load testing by PCR is more sensitive and may allow for pre-emptive treatment. However, the relationship between viremia and CMV infection is not perfect. The diagnosis can also be made by examination of infected tissue, as in CMV colitis.
In the current guidelines, either IV ganciclovir or oral valganciclovir are the recommended first-line agents, based on efficacy and lack of nephrotoxicity compared to cidofovir or foscarnet. Immunosuppression should be reduced if possible. CMV hyperimmune globulin may be used as an adjunct in patients with severe tissue-invasive disease. CMV viral load or antigenemia should be monitored weekly while on treatment, and antivirals should be continued for at least 1 week after the viral load becomes undetectable.