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  • The first part of the study evaluated the accuracy

    2019-08-05

    The first part of the study evaluated the accuracy of recomLine IgG and IgG Avidity to date CMV infection: In our study, 83.1% of samples tested matched onset dates compared to 71.9% with VIDAS avidity. Moreover, the number of inconclusive results (intermediate avidity for VIDAS, positive IgG without additional statement for recomLine) is smaller with the combination of line immunoassays (27% vs. 12.4%). Considering the performances of the combination of recomLine assays for timing primary infection according to the interpretations proposed by the manufacturer, we showed that their sensitivity to diagnose an infection <14 weeks is good (98%) even after including the inconclusive results (86%). An advantage of the recomLine assay should be its capacity to diagnose correctly infections >24 weeks,in order to rule out a primary infection during pregnancy when women attend prenatal care late after the first trimester. Unfortunately, our results showed a sensitivity of 16.67% (3/18) to exclude an infection <24 weeks. For the 15 other samples, the test scored correctly as infections >12 weeks, but this result does not help in the management of these women presenting late in the pregnancy. This poor sensitivity has also been observed by Enders et al. They did not obtain the characteristic blot pattern for late infection >24 weeks among a sample set of 30 infections >20–40 weeks. However, we have to mention that the manufacturer improved the quality of the antigen used for the recomLine assay compared to recomBlot tested by Enders, so the results may not be fully comparable. As mentioned by Enders et al., these results highlight the importance of performing CMV antibody testing during the first trimester or beginning of the second trimester in order to date correctly a primary infection (Enders et al., 2013). We observed also a low sensitivity of the recomLine assay to diagnose precisely an infection <6–8 weeks (34.38%, 11/32), but in this sample set, the test scored correctly the majority of the serum as infections <14 weeks (21/32). Conventional CMV IgG avidity assays have proved to be a helpful tool to date infection in pregnant women with positive CMV IgG and IgM; however, they give an intermediate or inconclusive result in 12–25% of cases, depending on the Bax inhibitor peptide V5 studied and the method used (Enders et al., 2014, Leruez-Ville et al., 2013, Prince and Lapé-Nixon, 2014, personal data). In the second part of our study, we showed that among the sample set of inconclusive results with VIDAS CMV IgG Avidity, the combination of line immunoassays could help to determine the timing of infection in 79% of samples. We took into account in these useful interpretations 2 negative and 1 borderline IgG. This is perhaps questionable, but as these samples were clearly positive with 2 different IgG immunoassays (and IgM positive), we considered that this information was useful, helping to suspect a very recent infection. Obviously, this has to be confirmed on a second sample. Considering the results of the second part of our study, the sequential use of conventional avidity testing followed by the line assays in case of inconclusive conventional avidity results may therefore help in the management of pregnant women presenting with a positive CMV IgG and IgM serology, especially during the first trimester of pregnancy. In conclusion, we assessed the performances of the Mikrogen recomLine CMV IgG and CMV IgG Avidity, and we demonstrated that this combination of line assays is useful as additional confirmatory testing and can help to date more precisely the onset of CMV primary infection.
    Conflict of interests
    Contributors
    Acknowledgments
    Introduction The implementation of effective prevention strategies has significantly reduced the incidence of cytomegalovirus (CMV) pneumonia after allogeneic hematopoietic stem transplantation (allo-HSCT); nevertheless, this clinical entity persists as a major clinical problem owing to poor survival, despite timely initiation of targeted antiviral therapy.1, 2 Currently, diagnosis of CMV pneumonia still remains a challenge. Proven CMV pneumonia can only be diagnosed using virological, histopathological or immunochemistry methods on biopsied lung tissue; this specimen type, however, is rarely obtained due to potential life-threatening complications. Traditionally, culture-based bronchoalveolar lavage (BAL) testing has been the mainstay for suggesting CMV involvement ex vivo, although detection of viable CMV in BAL fluids only points to a probable causality. Moreover, conventional virological procedures have been largely abandoned in most laboratories. Qualitative detection of CMV DNA in lung specimens by nucleic acid testing assays does not allow diagnosis of CMV pneumonia, since it may be present in the absence of probable or proven disease (pulmonary CMV shedding).5, 6, 7 Recent studies suggested that quantitation of CMV DNA in BAL fluids may permit discrimination between these two conditions–; specifically, a cut-off CMV DNA level >500 IU/ml was proposed to serve that purpose, this displaying a positive predictive value of roughly 50% for probable CMV pneumonia using current prevalence rates. Nevertheless, validation of diagnostic viral load threshold across centers using different real-time PCR assays for CMV DNA quantitation and procedures for BAL obtention seems of paramount relevance. This task is hampered by the very low incidence of CMV pneumonia nowadays (<2%)3, 12 and the difficulty in establishing an incontrovertible diagnosis, even when lung tissue specimens are available for testing.13, 14, 15– Exploratory studies gathering information on the range of CMV DNA loads measured in BAL specimens from allo-HSCT patients with pneumonia in whom CMV causality is unlikely or can be reasonably ruled out may provide useful information and are thus warranted. Here, we report on our experience on this matter.