A third-generation (gen.) screening and immunoblot assay (Ortho EIA-3.0; Chiron RIBA-3 prototype), using antigens derived from the capsid and different nonstructural regions (NS3, NS4 and NS5) of the hepatitis C virus viral genome, were evaluated in comparison with the corresponding second-gen. assays (Ortho EIA-2.0; revised Ortho EIA-2.5; Chiron RIBA-2). In 203 depository sera of blood donors, positive in EIA-2.0, specificity of the screening assays was improved as shown by an increase in positive predictive value for viral carrier state from 0.23 (EIA-2.0) to 0.37 (EIA-2.5) and 0.52 (EIA-3.0). Comparing the confirmation patterns on RIBA-2 and RIBA-3, this amelioration was mainly due to the specific elimination of false-positive c22-3 and c100-3 reactions. Antibody response to the newly added NS5 antigen was not as prevalent as to the other antigens and had only a minor influence in sample allocation. In contrast, screening of 1,560 volunteer blood donors and 47 hemodialysis patients revealed 3 additional positive sera, only reacting with the NS5 antigen. However none of these isolated NS5 reactions could be confirmed on synthetic peptides [INNO-LIA: NS5(p)] and none was PCR positive. A documented seroconversion, detected earlier with EIA-3.0, was related to a better immunological response to the NS3 antigen and not to the additional NS5. From this pilot study third-gen. assays appeared extremely useful in the reevaluation of HCV-seropositive depository sera. However the additional value of the NS5 antigen in blood donor screening is still hypothetical and remains to be established in larger screening studies.

Between February 1991 and January 1992, elevated alanine aminotransferase (ALT) levels were observed in several hemodialysis patients in a dialysis center in Dendermonde, Belgium. By the end of 1992, 25 out of 68 patients had seroconverted for HCV antibodies. The HCV strains from 23 of these seroconverters were genotyped and classified as genotype 1b. Sequence analysis of the HCV Core region was carried out in 12 patients, 9 of whom were infected with a strain bearing a unique sequence motif as compared with the currently known HCV 1b strains. A new 5' UR/Core line probe assay was designed to screen for such variations. Twenty patients tested positively for this special sequence motif, while the other 3 showed the regular subtype 1b sequence. Phylogenetic analysis of the Core sequences further revealed that the latter three were neither related to the main special strain of the infection, nor to each other. These three strains could be traced to two patients already infected at the time of residence in other dialysis units and to one patient who already showed ALT elevations in 1989. Epidemiological studies revealed no traceable source for this outbreak. In conclusion, molecular analysis demonstrates nosocomial transmissions by a peculiar genotype 1b strain in a dialysis center. Three other genotype 1b strains were also present in the unit, but were not responsible for the outbreak.

Summary The metabolism of human fibrinogen, labelled with radioactive iodine, was studied in 35 healthy subjects over a 5 yr period using eight fibrinogen preparations in 23 labelling procedures. The labelled fibrinogen was highly clottable and homogeneous on agarose gel filtration, immunoelectrophoresis and auto‐radiography. Results in the control subjects were: plasma volume 42 ± 7 ml/kg; plasma fibrinogen concentration 284 ± 71 mg/100 ml; total plasma fibrinogen pool 119 ± 40 mg/kg, representing 0.72 ± 0.07 of the total body pool; fibrinogen half‐life 4.14 ± 0.56 days; fractional catabolic rate 0.24 ± 0.04 of the plasma pool/day; fractional transcapillary efflux rate 0.60 ± 0.26 of the plasma pool/day. Comparable results were obtained for all labelled fibrinogen batches. Anticoagulation with heparin in five control subjects had no influence on the fibrinogen half‐life. Inhibition of the fibrinolytic system with tranexamic acid in five control subjects had no influence on the fibrinogen half‐life in four of them but resulted in a prolongation in one subject. A mathematical compartmental model for the metabolism of fibrinogen is proposed, consisting of one extra vascular compartment and three catabolic pathways (basic protein turnover, intravascular fibrin formation, and intravascular fibrino(geno)lysis). In physiological conditions intravascular fibrin formation or fibrino(geno)lysis are not essential in the fibrinogen turnover.

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