Clinical Review

INFECTIOUS DISEASE

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How to respond to a CMV diagnosis in pregnancy; worries over methicillin-resistant S. aureus infection in and out of pregnancy; more on HPV vaccination


 

References

Four studies caught my eye this past year. The first describes the use of systematic methodology to confirm the diagnosis of primary cytomegalovirus (CMV) infection in pregnancy and lower the rate of unnecessary pregnancy termination. Investigators were able to reclassify approximately 70% of women who had been diagnosed with CMV infection and reduce the number of pregnancy terminations by 73%.

Two other studies help define the emerging problem of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection, when to look for it, and how to treat it. In the first, researchers isolated S. aureus from the wounds of 320 patients with community-acquired infection and tested the samples for methicillin resistance, finding a prevalence of 59%. In the second study, investigators analyzed culture specimens from pregnant women for the presence of group B streptococci and S. aureus colonization. They found colonization with group B streptococci to be significantly associated with S. aureus colonization, with a prevalence odds ratio of 2.1.

The fourth study concerns the human papillomavirus (HPV) vaccine. Women given an HPV-16 L1 virus-like particle vaccine and followed for 4 years remained 100% free of cervical intraepithelial neoplasia (CIN) grades 2 and 3, unlike women who received placebo.

I believe these 4 studies represent the most significant developments of the past year in the field of infectious disease.

Don’t rush a diagnosis of CMV infection in pregnancy

Guerra B, Simonazzi G, Banfi A, et al. Impact of diagnostic and confirmatory tests and prenatal counseling on the rate of pregnancy termination among women with positive cytomegalovirus immunoglobulin M antibody titers. Am J Obstet Gynecol. 2007;196:221.e1–6.

CMV infection is a common and important perinatal pathogen. Each year in the United States, approximately 1% of gravidas acquire primary infection. Of these, about 40% transmit infection to the fetus. The rate of transmission is highest when maternal infection occurs in the third trimester, but the risk of serious fetal injury is greatest when maternal infection occurs in the first trimester. Ten percent to 20% of congenitally infected infants are acutely symptomatic at birth. Approximately 20% of these newborns die; most survivors have serious long-term complications. In contrast, CMV infection that recurs during pregnancy poses only minimal risk to the baby.1

Many women choose to have their pregnancy terminated when they learn they have a primary CMV infection.

Details of the study

This retrospective study was designed to determine whether a systematic diagnostic algorithm reduces the rate of unnecessary abortion in women who have apparent acute CMV infection during pregnancy. Guerra and colleagues evaluated 1,857 consecutive patients in practices in Italy who had a positive anti-CMV immunoglobulin M (IgM) antibody assay in the first or second trimester and were referred to a tertiary care facility for further diagnostic testing. Universal screening for CMV is now common among practitioners in Italy, and virtually all of these patients were completely asymptomatic.

At the tertiary facility, investigators tested again for CMV-specific IgM, as well as IgG, by enzyme immunoassay. They also tested for IgM by immunoblot and determined the avidity of anti-CMV IgG. Women who had IgG of low or moderate avidity with confirmed IgM, and those who clearly seroconverted to IgG were assumed to have a primary infection.

Women who were positive for IgM with high-avidity IgG were assumed to have nonprimary infection. Women who were seronegative for both antibodies were classified as uninfected. Those who were IgM-negative with high-avidity IgG were classified as previously infected. Women with an acute infection were then counseled by a specialist and offered amniocentesis and targeted ultrasonography.

Only 11.9% of women with primary infection chose abortion

Of the 1,857 women in this study, 445 were classified as having primary infection (group 1); 53 (11.9%) women elected to terminate their pregnancy. At autopsy, 38 of the 53 fetuses were found to be infected. In the other 15 cases, the pregnancy was terminated in the first trimester, and postmortem examination was not performed.

In the 1,205 women found to have nonprimary infection or previous infection (group 2), only 5 (0.4%) had the pregnancy terminated in the first trimester, and no postmortem examinations were performed. The difference in the observed rates of abortion between groups 1 and 2 was highly significant (P<.001).

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