Dear Editor,
Cytomegalovirus (CMV) is a ubiquitous DNA virus belonging to the herpes family that causes morbidity and mortality in immunosuppressed patients, particularly in those requiring blood transfusions, such as patients undergoing hemodialysis, organ transplant recipients, and individuals who lose blood following a serious accident or surgery (1).
CMV seropositivity rate among the adult populations worldwide ranges from 40% in the developed countries to 100% in the developing countries (1, 2). A seropositivity rate of 77.4% for anti-CMV immunoglobulin (Ig) G has been reported in Iran, showing evidence of a widespread previous CMV infection and increased CMV reactivation risk rate in the hosts (3).
Although several diagnostic tests, including virus culture, shell-vial assay, serological tests, antigenemia, and nested polymerase chain reaction (PCR), are available for either direct or indirect detection of human CMV infection, Nested PCR proved to be more sensitive for diagnosis of the infection than any other tests (1, 4).
In the developing countries, especially in Iran, the screening for cytomegalovirus infection is performed only for special groups of patients and is primarily based on the serological tests.
A total of 260 plasma samples of different patient groups, including 140 patients undergoing dialysis, 20 renal transplant recipients, 100 blood bags, were separately analyzed in our lab by utilizing serological assays for the detection of CMV IgM antibodies and by CMV-DNA amplification to diagnose active CMV infection (unpublished data). Of the 260 samples, 14 (5.4%) were positive for CMV infection. Viremia and anti-IgM CMV positivity were detected in 2.3% (6/260) and 3.07 % (8/260) samples, respectively. None of the samples was positive for both anti-IgM CMV and CMV-DNA. A time lapse between the CMV infection and production of IgM antibody is suggested, which is attributed to a delay in the immune system response. Therefore, CMV IgM antibodies might be undetectable during a primary infection in immunocompromised individuals. In addition, the IgM antibody may be detected up to 1 year after an acute infection. In this regard, the nested PCR assay may show a negative result (1, 4-6).
Our findings support many studies demonstrating the usefulness of serological tests for determining cytomegalovirus seroprevalence. Furthermore, the polymerase chain reaction test can be used for a rapid and accurate analysis, but relying entirely on the results of one test alone is not advisable. Therefore, a single test cannot be used for monitoring a previous or active (primary/reactivated) CMV infection (1, 4-7).
In conclusion, patients with renal failure may enlist for a kidney transplant or continue with dialysis. However, matching seronegative donors with seronegative recipients (blood/organs) is necessary to reduce the risk of CMV infection. Thus, CMV infection can be prevented by concomitant detection of IgM/IgG CMV antibodies and CMV DNA.
