Incidental mucocutaneous cytomegalovirus detection and its predictive value for systemic disease

Multiplex polymerase chain reaction (PCR) testing has revolutionised microbiological practice but also increased the number of positive results of uncertain significance. This phenomenon has been seen in the increasing detection of cytomegalovirus (CMV) in mucocutaneous swabs for herpesviruses, the microbiological significance of which is a priori unclear. The aim of our study was to determine if an incidental finding of a positive CMV result represented CMV disease, if it facilitated a timely diagnosis of CMV disease or whether there were any deleterious outcomes. We performed a retrospective review of patients with an incidentally positive PCR result for CMV on external and mucosal swabs, including medical comorbidities and presence of immunosuppression, subsequent investigations, whether a diagnosis of CMV disease was made, and treatment. CMV detection was infrequent, detected in 158 (3.4%) of 4626 herpes multiplex PCR tests performed. The majority (60.4%) of patients were immunocompromised, and amongst these patients a positive swab represented a new diagnosis or already known CMV disease in 14%. In seven patients (5%), all of whom were immunocompromised, the positive CMV PCR on a swab led to further investigation and subsequent diagnosis and treatment of CMV disease. Whilst not recommended for diagnosis of CMV disease, if CMV is detected on a mucocutaneous swab in an immunocompromised patient, further assessment and investigation for CMV disease should be undertaken.