Primary Cytomegalovirus Infection in Pregnant Egyptian Women Confirmed by Cytomegalovirus IgG Avidity Testing

Abstract

Objective: To determine the frequency of primary cytomegalovirus (CMV) infection in pregnant Egyptian women using CMV IgG avidity testing. Subjects and Methods: A cross-sectional study was conducted at Suez Canal University Hospital, Ismailia, Egypt. A total of 546 pregnant women, presenting for routine antenatal screening, were tested for CMV IgG and IgM using a commercially available enzyme-linked immunosorbent assay (ELISA). Sera from CMV IgM-positive women were tested by CMV IgG avidity assay. Results: All the 546 pregnant women were seropositive for anti-CMV IgG. Of the 546 women, 40 (7.3%) were positive or equivocal for IgM antibodies. All sera from the 40 women (IgG+/IgM+) showed a high or intermediate CMV IgG avidity index. Of the 40 women, 23 (57.5%) were in the second or third trimesters of pregnancy and had their first-trimester blood retrieved, and the tested CMV IgG avidity assay showed a high avidity index. Conclusion: Women who were IgM positive had no primary CMV infection in the index pregnancy as evidenced by the high CMV IgG avidity testing.

Value of immunoglobulin G avidity for primary cytomegalovirus diagnosis in pregnant women compared to nested polymerase chain reaction

“…In Egypt, a recent study reported the prevalence of IgG to be 100% and 7.3% for IgM. All samples with positive IgM in this study had a high AI (15).…”

“…Precedent study from Egypt revealed high rates of positive serological tests for HCMV between pregnant women (15).…”

Role of Cytomegalovirus (CMV) IgG Avidity Testing in Diagnosing Primary CMV Infection during Pregnancy

“…Many laboratories using CMV IgG avidity to discriminate primary from nonprimary CMV infection follow a reflexive algorithm whereby only CMV IgG-positive samples that are also CMV IgM positive are tested for CMV IgG avidity (6,17,18,31,34,48,58); yet, investigators that have tested all CMV IgG-positive samples for avidity, regardless of the CMV IgM result, have consistently found that 1% to 3% of IgG-positive, IgMnegative samples exhibit low IgG avidity (16,48,57), suggesting an increased risk of intrauterine transmission. Indeed, transmission has been documented in patients who lacked CMV IgM but exhibited low IgG avidity (14,61); it is likely that these women were in the narrow time window when IgM reversion has occurred but avidity is still low (3,(28)(29)(30)(31).…”

“…Studies assessing CMV IgG avidity showed that low CMV IgG avidity is both a sensitive and a specific marker of primary CMV infection (1-3). Indeed, CMV IgG avidity is increasingly considered the "gold standard" for distinguishing primary from nonprimary CMV infection (1,11,12,16) and is being used worldwide to identify primary CMV infection during pregnancy (14,(17)(18)(19)(20)(21).…”

“…Studies assessing CMV IgG avidity showed that low CMV IgG avidity is both a sensitive and a specific marker of primary CMV infection (1-3). Indeed, CMV IgG avidity is increasingly considered the "gold standard" for distinguishing primary from nonprimary CMV infection (1,11,12,16) and is being used worldwide to identify primary CMV infection during pregnancy (14,(17)(18)(19)(20)(21).This minireview focuses on 4 aspects of CMV IgG avidity testing: (a) the definition of avidity and the basic methodology used in initial studies linking CMV IgG avidity and primary infection; (b) a summary of results from the major studies demonstrating the utility of CMV IgG avidity assessment in pregnancy, including the advantages of avidity testing over CMV IgM testing alone; (c) a discussion of commercially available CMV IgG avidity assays, including newer automated assays; and (d) current issues and controversies in diagnosing primary CMV infections during pregnancy. …”