Amoebic liver abscess (ALA) is regularly seen in travelers or immigrants from tropical countries. The diagnosis relies on liver imaging that is not specific and on the detection of anti-Entamoeba histolytica antibodies, which cannot distinguish an acute from a former infection. We tested whether E. histolytica DNA detection in serum can improve the diagnosis of ALA. We retrospectively tested available serum samples taken from patients with ALA and non-ALA space-occupying lesions of the liver between 1 January 2010 and 30 November 2019. The quantitative PCR (qPCR) assay tested specifically amplifies a 99-bp fragment of the small-subunit rRNA gene of E. histolytica We analyzed 76 samples (19 ALA and 57 non-ALA samples) collected from 76 patients within 6 days before and after the antiamoebic treatment. Serum qPCR results were positive for 17 of 19 ALA patients and for none of the control patients (sensitivity and specificity were 89.5% and 100%, respectively). In parallel, the sensitivity and specificity of anti-E. histolytica antibody detection were 100% and 89.5%, respectively. The two false-negative qPCR results may be explained by ongoing metronidazole treatment or a possible persistent seropositivity that was not caused by the current liver abscess. Additionally, of 12 abscess pus aspirates (5 from ALA and 7 from non-ALA samples) tested, 5 were qPCR positive and 7 were qPCR negative, with concordant results in serum. This study demonstrates that cell-free circulating E. histolytica DNA can be detected in serum in ALA. This may assist in both positive diagnoses and treatment efficacy follow-up. The origin of this circulating DNA remains to be investigated.
Keywords: Entamoeba histolytica; PCR; abscesses; amoebiasis; amoebic liver abscess; cell-free nucleic acids; real-time PCR.
Copyright © 2020 American Society for Microbiology.