Elina Kolho

Transmission of HCV infection by RIBA indeterminate and positive blood units

SUMMARY. A retrospective study was carried out on the recipients of 73 units of blood from 53 donors found reactive for anti‐HCV. The donors were screened with anti‐HCV enzyme‐linked immunosorbent assay (ELISA C‐100) and reactivity was confirmed with the first generation recombinant immunoblot assay (RIBA I). Fifty‐two patients were recipients of blood from donors reacting as RIBA I ‘indeterminate’ and 21 of blood from RIBA I ‘positive’ donors. Only three recipients (5.8%) from ‘indeterminate’ donors were anti‐HCV positive indicating that such donors are very seldom infectious. Eleven (52.4%) recipients from ‘positive’ donors had antibodies to HCV, indicating that not all RIBA‐positive donors are necessarily infectious. Pretransfusion samples of the seropositive recipients were unavailable. All samples were analysed with the first generation ELISA and with either the second‐generation ELISA or RIBA (RIBA II) in order to evaluate test sensitivity. RIBA II was more sensitive than RIBA I. One RIBA I indeterminate donor was positive by RIBA II. His recipient had antibodies to HCV. Twelve RIBA I indeterminate and three RIBA I positive donors were negative by RIBA II. All their recipients were anti‐HCV negative. The second‐generation ELISA was also shown to be more sensitive than ELISA C‐100. The second‐generation ELISA detected six confirmed anti‐HCV positive recipients who were negative by ELISA C‐100.

Outbreak caused by Tobramycin-resistant Pseudomonas aeruginosa in a Bone Marrow Transplantation Unit

Between May and August 1995, 5 patients in a bone marrow transplantation (BMT) ward developed bacteremia caused by Pseudomonas aeruginosa resistant to tobramycin (TRPA). Previously, isolates of TRPA had been limited to patients who were treated in 1 intensive care unit (ICU) of this tertiary care teaching hospital in Helsinki, Finland. To study whether the outbreak was caused by a single or multiple strains of P. aeruginosa, 102 isolates of TRPA from clinical samples obtained from different hospital units and 22 isolates obtained from the hospital environment were characterized by pulsed-field gel electrophoresis. All isolates from hematological patients produced 1 unique fragment pattern, which was also isolated from 3 ICU patients before the BMT ward outbreak began as well as from 5 shower heads in the BMT ward. The outbreak in the BMT ward was successfully controlled by eradicating the probable environmental source ? contaminated hand showers ? but the endemic infections continued in the ICU.Between May and August 1995, 5 patients in a bone marrow transplantation (BMT) ward developed bacteremia caused by Pseudomonas aeruginosa resistant to tobramycin (TRPA). Previously, isolates of TRPA had been limited to patients who were treated in 1 intensive care unit (ICU) of this tertiary care teaching hospital in Helsinki, Finland. To study whether the outbreak was caused by a single or multiple strains of P. aeruginosa, 102 isolates of TRPA from clinical samples obtained from different hospital units and 22 isolates obtained from the hospital environment were characterized by pulsed-field gel electrophoresis. All isolates from hematological patients produced 1 unique fragment pattern, which was also isolated from 3 ICU patients before the BMT ward outbreak began as well as from 5 shower heads in the BMT ward. The outbreak in the BMT ward was successfully controlled by eradicating the probable environmental source--contaminated hand showers--but the endemic infections continued in the ICU.

Transmission of Hepatitis C Virus to Sexual Partners of Seropositive Patients with Bleeding Disorders: A Rare Event

Sexual transmission of hepatitis C virus (HCV) was studied in 30 partners to anti-HCV positive multitransfused patients with a bleeding disorder. Anti-HCV ELISA C-100 was used as a screening test. Positive results were confirmed with the first generation RIBA test. Indeterminate samples were tested also with the second generation RIBA to verify the positivity. The time of sexual exposure added up was at least 95 years. 29 partners were anti-HCV seronegative. Only 1 partner was anti-HCV indeterminate. Thus sexual transmission of HCV was a rare event.

Specificity and sensitivity of first and second generation anti-HCV ELISA in a low prevalence population

SUMMARY. Specificity and sensitivity of the second generation enzyme immunosorbent assay for hepatitis C antibodies were calculated from data on 208,554 blood donors screened with either the first or the second generation tests (ELISA I, ELISA II) or both (4,639 donors). The second generation ELISA was no more specific than the first generation test in this low‐prevalence blood donor population (specificity 99.7% vs 99.6%). Most of the donors (93.5%) who were found to be reactive using ELISA II were negative or indeterminate according to a supplemental test, the second generation recombinant immunoblot assay (RIBA II). The second generation ELISA was found to be more sensitive than the first. It identified all 16 donors who were positive according to RIBA II during screening with ELISA I. The latter found only 13 out of 30 donors (43%) who were positive according to RIBA II during screening with ELISA II. If the number of RIBA II positive donors found during the first year of screening with ELISA I (74, 0.024%), and the number of RIBA II positive but ELISA I negative donors found during screening with ELISA II, are taken into consideration it can be estimated that the added sensitivity due to using ELISA II is about 40%.

Specificity and Sensitivity of Two Second‐Generation ELISA Tests in Detecting Hepatitis C Antibodies in Blood Donors Known to Be Reactive with a Supplemental Assay

Two years ago, the major causative agent of non-A, non-B hepatitis called hepatitis C virus (HCV) was cloned, and a serologic assay to detect antibody to the non-structural HCV C-100 antigen was developed [l, 21. HCV ELISA C-100 is, however, non-specific in a lowprevalence population [3,4]. Supplemental tests improve specificity, but are not applicable to blood donor screening [5-71. New second-generation ELISAs based on both non-structural and structural antigens have been developed in order to improve both the specificity and the sensitivity. Limited data concerning the specificity of the tests are still available. All blood donors in Finland have been tested for antiHCV since April 1990 using Ortho ELISA c-100 for screening. By the end of November 1990, altogether 207,064 donors had been screened. Of these, 1,241 (0.59%) were repeatedly reactive by ELISA C-100, out of which 130 (10.5%) were indeterminate (8 donors reactive to both HCV and SOD antigens excluded) and 46 (3.7%) positive by a supplemental test, Chiron first-generation recombinant immunoblot assay (RIBA-2). The RIBA-2 result was confirmed by testing a follow-up sample. Two RIBA-2-indeterminate and 1 RIBA-2-positive donors did not send a follow-up sample and were therefore excluded. All the rest, 173 donors, were analysed by two secondgeneration ELISAs, namely, (1) the Ortho second-generation ELISA test (ELISA A) based on antigens C22-3, a structural protein, and C200, a non-structural protein, and (2) the United Biomedical Inc. HCV EIA test (ELISA B) based on synthetic peptides representative of both the structural and non-structural region of the HCV genome. All samples were also analysed with the secondgeneration Chiron recombinant immunoblot assay (RI-

Specificity and sensitivity of two second‐generation enzyme‐linked immunosorbent assays for antibodies to hepatitis C virus in blood donor screening

I have no argument whatsoever in regard to compliance with the law. However, the fact that a set of regulations has been enacted does not automatically confer on those regulations unimpeachable rightness and truth. It is long past time for the transfusion medicine profession to speak up loudly and clearly when regulations or laws affecting our operations are inappropriate or are unevenly applied.