Intravenous immunoglobulin infusion contributes to a high incidence of false reactive screen results for human T-lymphotropic virus.

Intravenous immunoglobulin (IVIg) has been increasingly used to treat immunodeficiencies and inflammatory disorders. However, IVIg has also been shown to affect a wide range of laboratory testing, including human T-lymphotropic virus (HTLV) screening. Our laboratory frequently observes false reactive HTLV screens from patients receiving IVIg infusions, however the extent of IVIg contribution to the false reactivity has not been extensively investigated. The objective of this study was to explore the prevalence of HTLV-1/2 infection in patients from the Sydney metropolitan area and evaluate the positive predictive value for HTLV screening test in sera from patients with or without IVIg infusions. HTLV screening test results from sera of 3843 patients referred to Central Sydney Immunology Laboratory between June 2006 and May 2021 were retrospectively analysed. Among 72 (1.9%) sera reactive on screening enzyme-linked immunosorbent assay (ELISA), 62 (86.1%) were from patients receiving IVIg infusions, including 60 collected post-IVIg and two collected pre-IVIg infusions. Only two (3.3%) of the 60 post-IVIg sera were positive on confirmatory western blot. In contrast, in non-IVIg sera, five (50.0%) from the 10 screen-reactive sera were positive on western blot. If positive western blot is used as the reference for determining 'true' HTLV infection, we found the positive predictive value of HTLV screening ELISA in sera collected post-IVIg (3.3%) is considerably lower than that in non-IVIg and pre-IVIg sera (41.7%). The vast majority of false reactive screen results (89.2%) in our study cohort were from sera collected post-IVIg infusion. Our study suggests that the high incidence of falsely reactive results in HTLV screening ELISA could be attributed to IVIg infusion. Hence, collection of sera from patients on IVIg should be avoided and screen-reactive results should be interpreted with greater caution, particularly for patients from non-endemic areas.

A cost-effective sample pooling strategy for line blot assay in detecting onconeural antibodies.

BACKGROUND: Onconeural antibodies are a group of autoantibodies present in patients with paraneoplastic syndromes (PNS), and are indicative for underlying malignancies. The use of indirect immunofluorescence assay (IFA) as the sole screening method for onconeural antibodies without line blot assay (LBA) could potentially miss a significant population of patients with PNS. However, testing each serum individually on LBA will pose significant economical and labour burdens to clinical laboratories. Based on the screening result from IFA, we developed a cost-effective pooling strategy for the detection of onconeural antibodies on LBA. METHODS: Results of onconeural antibodies tested by IFA and LBA from 1887 serum samples received in the Central Sydney Immunology Laboratory were retrospectively analysed. Sera were pre-screened by IFA before proceeding to LBA. Sera with positive staining on IFA were tested individually on LBA while sera with negative IFA were examined by pooling. Agreements of antibody reactivity against onconeural antigens were evaluated for sera run by pooling and by individually. The estimate of the cost saving was also conducted for the pooling strategy. RESULTS: Antibody reactivity to each specific onconeural antigen from pooling run had over 95% qualitative result agreement with sera run individually on LBA. An excellent correlation (r = 0.88) of positive reactions quantitated by band signal intensity was also observed. Using our well-established sera pooling strategy for LBA, a cost saving of 50.1% was achieved for reagent alone. CONCLUSIONS: The sera pooling strategy for LBA is a reliable and cost-effective approach for testing low prevalence diseases such as PNS.

Longitudinal ex vivo and molecular trends of chloroquine and piperaquine activity against Plasmodium falciparum and P. vivax before and after introduction of artemisinin-based combination therapy in Papua, Indonesia.

Drug resistant Plasmodium parasites are a major threat to malaria control and elimination. After reports of high levels of multidrug resistant P. falciparum and P. vivax in Indonesia, in 2005, the national first-line treatment policy for uncomplicated malaria was changed in March 2006, to dihydroartemisinin-piperaquine against all species. This study assessed the temporal trends in ex vivo drug susceptibility to chloroquine (CQ) and piperaquine (PIP) for both P. falciparum and P. vivax clinical isolates collected between 2004 and 2018, by using schizont maturation assays, and genotyped a subset of isolates for known and putative molecular markers of CQ and PIP resistance by using Sanger and next generation whole genome sequencing. The median CQ IC50 values varied significantly between years in both Plasmodium species, but there was no significant trend over time. In contrast, there was a significant trend for increasing PIP IC50s in both Plasmodium species from 2010 onwards. Whereas the South American CQ resistant 7G8 pfcrt SVMNT isoform has been fixed since 2005 in the study area, the pfmdr1 86Y allele frequencies decreased and became fixed at the wild-type allele in 2015. In P. vivax isolates, putative markers of CQ resistance (no pvcrt-o AAG (K10) insertion and pvmdr1 Y967F and F1076L) were fixed at the mutant alleles since 2005. None of the putative PIP resistance markers were detected in P. falciparum. The ex vivo drug susceptibility and molecular analysis of CQ and PIP efficacy for P. falciparum and P. vivax after 12 years of intense drug pressure with DHP suggests that whilst the degree of CQ resistance appears to have been sustained, there has been a slight decline in PIP susceptibility, although this does not appear to have reached clinically significant levels. The observed decreasing trend in ex vivo PIP susceptibility highlights the importance of ongoing surveillance.