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In the United Kingdom, organ donors/recipients are screened for evidence of human T-cell leukaemia virus type-1 and type-2 (HTLV-1/2) infections. Since the United Kingdom is a low prevalence country for HTLV infections, a screening assay with high sensitivity and specificity is required. Samples with repeat reactivity on antibody testing are sent to a reference lab for confirmatory serological and molecular testing. In the case of donor screen, this leads to delays in the release of organs and can result in wastage. We aim to assess whether a signal/cut-off (S/CO) ratio higher than the manufacturer's recommendation of 1.0 in the Abbott Architect antibody assay is a reliable measure of HTLV-1/2 infection.We conducted a 5 year retrospective analysis of 7245 patients from which 11 766 samples were tested on the Abbott Architect rHTLV I/II assay. Reactive samples (S/CO 1) were referred for confirmatory serological and molecular detection (Western Blot and proviral DNA) at UK Health Security Agency, (formerly PHE, Colindale), the national reference laboratory. Electronic, protected laboratory and hospital patient databases were employed to collate data.A total of 45 patients had initially reactive samples. 42.2% (n = 19/45) had an S/CO ratio 20, with HTLV infection confirmed in n = 18/19 and indeterminate confirmatory results in n = 1/19. No samples with an S/CO ratio4 (48.9%, n = 22/45) or 4-20 (8.9%, n = 4/45) had positive confirmatory results on subsequent confirmatory testing.Samples with an S/CO20 likely represent a true HTLV-1/2 infection. Reactive samples with an S/CO 4 were unlikely to confirm for HTLV infections. Interpretation of these ratios can assist clinicians in the assessment of low reactive samples and reiterates the need for faster access to confirmatory testing.

Hepatitis C virus (HCV) seroconversion was detected by routine screening in a haemodialysis patient, Patient 1. Serological investigations were undertaken over the following 3 months to determine if further transmission to other patients on the unit had occurred. No additional cases were identified. Twenty-two haemodialysis patients known to have HCV infection were investigated using molecular epidemiological methods to determine if transmission between patients had occurred. HCV viraemia was demonstrated by polymerase chain reaction in 19 of 22 patients (86%). Genotyping showed that eight patients were infected with genotype 1, three with genotype 3 and eight, including Patient 1, with genotype 2. Phylogenetic analysis of viral sequences from the eight patients with genotype 2 revealed three, including Patient 1,with a novel subtype of HCV type 2, and revealed close similarity between viral sequences from patient 1 and those from one other patient, suggesting transmission. This was consistent with haemodialysis histories. Among other patients with genotype 2, there were two with subtype 2a and three others with three separate novel subtypes, as yet undesignated. With the exception of patient 1, all patients infected with novel subtypes were of Afro-Caribbean origin. The HCV prevalence among patients on the haemodialysis unit was high (14%), which may reflect the ethnicity of our haemodialysis population. This case emphasises the risk of nosocomial transmission and the importance of infection control procedures on haemodialysis units, and highlights the usefulness of molecular epidemiological techniques for the investigation of outbreaks of HCV infection.