Very low hepatitis C antibody levels predict false-positive results and avoid supplemental testing

BACKGROUND: False‐positive results for hepatitis C virus antibody (anti‐HCV) occur with unacceptable frequency in low‐prevalence populations. The purpose of the study was to determine whether signal‐to‐cutoff (S/CO) ratios of anti‐HCV assay–reactive samples could be used to discriminate false‐positive from true‐positive anti‐HCV results and avoid the need for supplemental testing. STUDY DESIGN AND METHODS: Using receiver‐operating characteristic curve, the cutoff point that identifies the major proportion (≥95%) of false‐positive results, with a minor proportion (<5%) of true‐positive anti‐HCV results, was determined. An anti‐HCV assay (VITROS, Ortho Clinical Diagnostics) was used to detect the antibodies. The third‐generation recombinant immunoblot assay and HCV RNA tests were performed on all included donors. Third‐generation RIBA is the gold standard for identifying false‐positive antibody results. RESULTS: A total of 649 anti‐HCV–positive blood donors were identified. A S/CO ratio of less than 4.5, defining very low levels in this value, was the optimal cutoff point to identify false‐positive results; 315 of 322 samples with very low levels were false‐positive anti‐HCV results (97.8%; 95% confidence interval [CI], 95.8%‐99.0%) and 7 were true‐positive (2.2%; 95% CI, 1.0%‐4.3%). Viremia was detected in none of them. A direct relationship was observed between positive supplemental testing and increased antibody levels in the other 327 samples. CONCLUSION: The high prediction rate of false‐positive anti‐HCV results using very low levels by the Ortho VITROS anti‐HCV assay safely avoids the need for supplemental testing.     

Human T-lymphotropic virus antibody screening of blood donors: rates of false-positive results and evaluation of a potential donor reentry algorithm

BACKGROUND: Blood donor screening with enzyme immunoassays (EIAs) for antibodies to human T‐lymphotropic virus (HTLV)‐I, and later to HTLV‐I/II, has led to the unnecessary deferral of tens of thousands of individuals. The licensure of the Abbott PRISM HTLV‐I/HTLV‐II chemiluminescent immunoassay (ChLIA) may permit the reinstatement of historically deferred donors. STUDY DESIGN AND METHODS: The efficacy of a reentry algorithm involving a follow‐up sample from EIA‐deferred donors testing HTLV‐I/II ChLIA nonreactive was evaluated using 386 serologic confirmed‐positive samples archived since the inception of anti‐HTLV donor screening. Reactivity of the 386 samples by the ChLIA, when coupled with the package insert sensitivity data, may be used to demonstrate efficacy of the reentry algorithm. Donor incidence was also examined from 2008 through 2009 to evaluate changes to the existing HTLV screening policy. RESULTS: From January 1, 1995, to April 28, 2008, a total of 64,052 donors to the American Red Cross were deferred solely because of HTLV EIA false positivity, representing more than 130,000 US donors. HTLV ChLIA identified 386 confirmed‐positive donations from 386 randomly selected donors representing reactivity to both the bioMérieux and the Abbott HTLV‐I/II EIAs (95% confidence interval [CI], 99.2%‐100%); both EIAs have since been discontinued. This is comparable to the detection of 843 of 843 confirmed‐positive samples during the ChLIA clinical trials (95% CI, 99.48%‐100%). Incident HTLV infections occurred primarily among female repeat donors during 2008 throughout 2009. CONCLUSIONS: Donors testing falsely positive by historic EIAs since 1988 should be considered for reinstatement if a contemporary sample tests ChLIA nonreactive. Changes to the existing screening algorithm seem unlikely since new HTLV infections were detected among repeat donors.     

The clinical relevance of persistent recombinant immunoblot assay-indeterminate reactions: insights into the natural history of hepatitis C virus infection and implications for donor counseling

BACKGROUND: Recombinant immunoblot assay (RIBA) is used to determine the specificity of antibody to hepatitis C virus (anti‐HCV). The RIBA result is recorded as positive, negative, or indeterminate. The interpretation and significance of RIBA‐indeterminate reactions are unclear. We addressed the clinical relevance of these reactions in the context of the natural history of HCV infection in a prospectively followed cohort of anti‐HCV–positive blood donors. STUDY DESIGN AND METHODS: Donor demographics, exposure history, and humoral and cell‐mediated immunity (CMI) were compared in 15 RIBA‐indeterminate subjects, nine chronic HCV carriers, and eight spontaneously recovered subjects. Serum samples were tested for anti‐HCV by a quantitative, liquid luciferase immunoprecipitation system (LIPS). CMI was assessed by interferon‐γ enzyme‐linked immunosorbent spot assay. RESULTS: In the LIPS assay, the sum of antibody responses to six HCV antigens showed significant (p < 0.001) stepwise diminution progressing from chronic carriers to spontaneously recovered to RIBA‐indeterminate subjects. CMI responses in RIBA‐indeterminate subjects were similar to spontaneously recovered subjects and greater than chronic carriers and controls (p < 0.008). A parenteral risk factor was identified in only 13% of RIBA‐indeterminate subjects compared to 89% of chronic carriers and 87% of spontaneously recovered subjects. RIBA‐indeterminate donors were older than the other groups. CONCLUSION: The CMI and LIPS results suggest that persistent RIBA‐indeterminate reactions represent waning anti‐HCV responses in persons who have recovered from a remote HCV infection. In such cases, detectable antibody may ultimately disappear leaving no residual serologic evidence of prior HCV infection, as reported in a minority of long‐term HCV‐recovered subjects.     

A case‐control study of factors associated with resolution of hepatitis C viremia in former blood donors (CME)

BACKGROUND: Nucleic acid testing (NAT) is performed on blood collected in the United States allowing for the classification of hepatitis C virus (HCV) antibody–positive donors into resolved and chronic hepatitis C infections. We report a case‐control study of factors associated with HCV resolution. STUDY DESIGN AND METHODS: Blood donors with resolved (HCV antibody positive, RNA negative defined as “cases”) or chronic (HCV antibody positive, RNA positive defined as “controls”) based on their index donation HCV test results were enrolled. Participants completed a risk factor, symptoms, and treatment questionnaire followed by HCV antibody, HCV RNA, and liver biochemical testing. RESULTS: We enrolled 100 cases and 202 controls. In a multivariate logistic regression model, significant independent effects for spontaneous viral clearance were observed for African American (inverse; odds ratio [OR], 0.11; 95% confidence interval [CI], 0.01‐0.87), autologous blood donation (OR, 4.70; 95% CI, 2.02‐10.94), alcohol intake (OR, 2.39; 95% CI, 1.13‐5.03), and transfusion before May 1990 (inverse; OR, 0.36; 95% CI, 0.14‐0.91). Cases admitting injection drug use had shorter time since first injection than did controls. Forty‐nine index RNA positive controls received antiviral therapy and 25 (51%) were RNA negative at enrollment; surprisingly several RNA‐negative cases received liver biopsies and/or antiviral treatment. CONCLUSIONS: We document the role donor screening plays in the identification, subsequent medical evaluation, and treatment among individuals who presumably did not know that they were at risk for HCV infection. Additionally, we confirmed race/ethnicity as a determinant of clearance and suggest infectious dose and route of infection may play a role in clearance.     

Prevalence of serologic markers for hepatitis B and C viruses in Brazilian blood donors and incidence and residual risk of transfusion transmission of hepatitis C virus

BACKGROUND: We evaluate the current prevalence of serologic markers for hepatitis B virus (HBV) and hepatitis C virus (HCV) in blood donors and estimated HCV incidence and residual transfusion‐transmitted risk at three large Brazilian blood centers. STUDY DESIGN AND METHODS: Data on whole blood and platelet donations were collected from January through December 2007, analyzed by center; donor type; age; sex; donation status; and serologic results for hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti‐HBc), and anti‐HCV. HBV and HCV prevalence rates were calculated for all first‐time donations. HCV incidence was derived including interdonation intervals that preceded first repeat donations given during the study, and HCV residual risk was estimated for transfusions derived from repeat donors. RESULTS: There were 307,354 donations in 2007. Overall prevalence of concordant HBsAg and anti‐HBc reactivity was 289 per 100,000 donations and of anti‐HCV confirmed reactivity 191 per 100,000 donations. There were significant associations between older age and hepatitis markers, especially for HCV. HCV incidence was 3.11 (95% confidence interval, 0.77‐7.03) per 100,000 person‐years, and residual risk of HCV window‐phase infections was estimated at 5.0 per million units transfused. CONCLUSION: Improvement in donor selection, socioeconomic conditions, and preventive measures, implemented over time, may have helped to decrease prevalence of HBV and HCV, relative to previous reports. Incidence and residual risk of HCV are also diminishing. Ongoing monitoring of HBV and HCV markers among Brazilian blood donors should help guide improved recruitment procedures, donor selection, laboratory screening, and counseling strategies.     

Results of HCV screening of volunteer blood donors with a chemiluminescent immunoassay and a second- or third-generation EIA: overlap of false-positive reactivity and its impact on donor management

BACKGROUND: This study reports the results of adopting a strategy of anti-HCV testing of volunteer blood donors that uses a primary screening assay, two secondary EIAs (Anti-HCV Version III, Murex; Monolisa Anti-HCV New Antigens, Sanofi Pasteur), and a confirmatory immunoblot (HCV WB, Murex). STUDY DESIGN AND METHODS: A comparison was made of HCV test results from volunteer donors tested in two periods when different primary HCV screening assays were in use. The same two secondary screening assays and the same confirmatory test were used for the whole study. The two different primary assays were semi-automated second- or third-generation HCV EIA (Abbott Diagnostics) and an HCV chemiluminescent immunoassay (ChLIA), performed on a fully automated analyzer (PRISM, Abbott). RESULTS: During the period of use of the EIAs as primary screening assays, there were 60 donors per year who were confirmed as anti-HCV-positive, 29 who were classed as having indeterminate HCV serologic results, and 236 who were assessed as having biologically false-positive anti-HCV results. These numbers compared with 57, 52, and 320 such donors, respectively, in the first year of routine use of the ChLIA. The significant increase (p<0.05) in the number of anti-HCV-indeterminate donors after the introduction of the ChLIA was primarily due to an increase in donors who reacted on Monolisa HCV, but not an HCV Murex (expected 18/year vs. the observed 31/year, p<0.01). CONCLUSIONS: Compared to the second- or third-generation HCV EIA, the HCV ChLIA has a significantly greater overlap of false reactivity with the Monolisa HCV assay. This finding has implications for the selection of primary and secondary assays for anti-HCV screening of blood donors.     

The increasing prevalence of serologic markers for syphilis among Chinese blood donors in 2008 through 2010 during a syphilis epidemic

BACKGROUND: In China, the growing syphilis epidemic parallels the spread of human immunodeficiency virus (HIV) in the general population. This study evaluated the prevalence and incidence of serologic markers for syphilis among donors at five Chinese blood centers. STUDY DESIGN AND METHODS: We examined whole blood and apheresis donations collected from January 2008 through December 2010. Postdonation testing of syphilis was conducted using two different Treponema pallidum antibody enzyme‐linked immunosorbent assay kits. The prevalence of serologic markers for syphilis (%), and the rate of coinfection with HIV‐1/2, hepatitis B virus (HBV), and hepatitis C virus (HCV) were calculated. A multivariable logistic regression analysis was conducted examining donor characteristics associated with positive syphilis serology. Seroconversion rate and syphilis incidence were estimated. RESULTS: Of 801,511 donations, 60% were from first‐time donors and 40% were from repeat donors. There was a significant increase in syphilis serologic markers among first‐time donors with 0.41, 0.45, and 0.57% positivity over 3 years (p < 0.001). Approximately 2.8, 0.8, and 0.5% of HIV‐1/2–, HBV‐, and HCV‐positive donations also tested reactive for syphilis. Logistic regression results suggest that first‐time donors were nine times more likely to be syphilis positive than repeat donors. Higher syphilis positivity was associated with donors older than 25 years and with less education. Estimated incidence among repeat donations was 33 (95% confidence interval, 29‐39) per 100,000 person‐years. CONCLUSION: The increase in syphilis serologic prevalence reflected the syphilis epidemic in the general population. Without screening, most of these syphilis‐positive donations would get into the blood supply. Thus, during a syphilis epidemic, continued syphilis screening of blood donations may be important to maintain blood safety and public health.     

Hepatitis C antibody intraassay correlation: is retest in duplicate necessary?

BACKGROUND: The hepatitis C virus antibody (anti-HCV) can be identified with third-generation immunoassays. The purpose of this study was to define the correlation or agreement between first and second reactive results of anti-HCV microparticle-based enzyme immunoassay (MEIA) and of chemiluminescence assays (ChLIAs) in blood donors, to determine whether repeat testing is necessary. STUDY DESIGN AND METHODS: Commercially available assays, third-generation HCV MEIA (Abbott), third-generation HCV ChLIA (Ortho), and third-generation HCV ChLIA (Abbott), were used to evaluate anti-HCV repeatedly reactive blood obtained from donations made at 23 Mexican blood centers over a period of 1 year. The intraassay correlation between first and second reactive anti-HCV tests with the Pearson r test and the coefficient of variation (CV) were determined. RESULTS: The intraassay correlation of 565 anti-HCV repeatedly reactive samples was 0.996 for the Abbott third-generation HCV MEIA, 0.995 for the Ortho third-generation HCV ChLIA, and 0.993 for the Abbott third-generation HCV ChLIA. The CVs of these assay systems were 2.82, 5.33, and 5.69 percent, respectively. CONCLUSION: A highly significant intraassay correlation between anti-HCV duplicates was found. Specimens with a single reactive anti-HCV result with the Abbott third-generation HCV MEIA, Ortho third-generation HCV ChLIA, and Abbott third-generation HCV ChLIA assays should be considered as positive and need not be retested. Such a change in the algorithm for blood donor screening is feasible because of the availability of highly automated platforms.     

Multicenter comparison of serologic assays and estimation of human herpesvirus 8 seroprevalence among US blood donors

BACKGROUND: As part of assessing the possibility of transfusion transmission of human herpesvirus 8 (HHV-8 or Kaposi's sarcoma-associated herpesvirus), HHV-8 seroprevalence was estimated among US blood donors, the performance of HHV-8 serologic tests was compared, and the presence of HHV-8 DNA was tested for in donated blood. STUDY DESIGN AND METHODS: Replicate panels of 1040 plasma specimens prepared from 1000 US blood donors (collected in 1994 and 1995) and 21 Kaposi's sarcoma patients were tested for antibodies to HHV-8 in six laboratories. HHV-8 PCR was performed on blood samples from 138 donors, including all 33 who tested seropositive in at least two laboratories and 22 who tested positive in at least one. RESULTS: The estimated HHV-8 seroprevalence among US blood donors was 3.5 percent (95% CI, 1.2%-9.8%) by a conditional dependence latent-class model, 3.0 percent (95% CI, 2.0%-4.6%) by a conditional independence latent-class model, and 3.3 percent (95% CI, 2.3%-4.6%) by use of a consensus-derived gold standard (specimens positive in two or more laboratories); the conditional dependence model best fit the data. In this model, laboratory specificities ranged from 96.6 to 100 percent. Sensitivities ranged widely, but with overlapping 95 percent CIs. HHV-8 DNA was detected in blood from none of 138 donors evaluated. CONCLUSIONS: Medical and behavioral screening does not eliminate HHV-8-seropositive persons from the US blood donor pool, but no viral DNA was found in donor blood. Further studies of much larger numbers of seropositive individuals will be required to more completely assess the rate of viremia and possibility of HHV-8 transfusion transmission. Current data do not indicate a need to screen US blood donors for HHV-8.     

Hepatitis C virus RNA in serum of blood donors with or without elevated transaminase levels

The pattern of hepatitis C virus (HCV) viremia in blood donors who are positive for antibody to HCV (anti-HCV) according to the level of transaminase activity is unclear. A polymerase chain reaction-based HCV RNA detection method was used to study two clearly defined groups of anti-HCV-positive blood donors with repeatedly normal (n = 27) and elevated (n = 17) alanine aminotransferase (ALT) levels. HCV RNA was detected in only 4 of 27 blood donors with normal ALT values and 15 of 17 with elevated ALT values. These results indicate that anti-HCV- positive blood donors with normal ALT levels constitute a heterogeneous group, as HCV viremia is detectable in only a small proportion of cases. Polymerase chain reaction should be useful in the surveillance of anti-HCV-positive blood donors with normal ALT levels, by identifying those who might benefit from further investigation and treatment.     

Relative safety of first‐time volunteer and replacement donors in West Africa

BACKGROUND: A significantly higher level of safety between nonremunerated volunteer and replacement donor blood is assumed. This is supported by global data without stratifying between genuine replacement and paid donors, for first‐time or repeat volunteer, or according to age. STUDY DESIGN AND METHODS: In 2008, first‐time volunteer and replacement donors were identified, and confirmed human immunodeficiency virus antibody (anti‐HIV), hepatitis B surface antigen (HBsAg), and hepatitis C virus antibody (anti‐HCV)‐positive screening results were collated. Data were analyzed according to age and sex between the two types of donors. RESULTS: In 6640 first‐time volunteer and 4360 replacement donors, the prevalence of anti‐HIV and HBsAg (1.03 and 13.8% vs. 1.1 and 14.9%, respectively) was not significantly different. Anti‐HIV prevalence was higher in replacement donors less than age 20 than in first‐time volunteers; the difference was not significant. HBsAg and anti‐HIV confirmed‐positive prevalence was significantly higher in first‐time volunteer donors over age 20. CONCLUSION: In Kumasi, Ghana, viral safety of replacement and first‐time volunteer donors was similar, constituting a single population of donors. Safety increment is provided by repeat donation applicable to either group, through different approaches. A blood unit from replacement donor costs half or less than that from a volunteer donor; similar studies conducted elsewhere in sub‐Saharan Africa may lead to changes in current strategies.     

Analysis of sample‐to‐cutoff ratios on chemiluminescent immunoassays used for blood donor screening highlights the need for serologic confirmatory testing

BACKGROUND: High sample‐to‐cutoff (s/co) ratios on hepatitis C virus antibody (anti‐HCV) screening immunoassays (IAs) are indicative of confirmed‐positive results and, according to some reports, can be used to determine anti‐HCV status without the need for confirmatory testing. The purpose of this study was to determine whether s/co ratios on hepatitis B surface antigen (HBsAg), antibody to human immunodeficiency virus Types 1 and 2 (anti‐HIV‐1/2), anti‐HCV, and antibody to human T‐lymphotropic virus Types I and II (anti‐HTLV‐I/II) chemiluminescent immunoassays (ChLIAs) can be used to discriminate between biologic false‐reactive (BFR) and confirmed‐positive results. STUDY DESIGN AND METHODS: In a blood donor population the s/co ratio distributions for BFR and confirmed‐positive results were compared for the Abbott PRISM HBsAg, HIV O Plus, HCV, and HTLV‐I/II ChLIAs to determine the extent of overlap between the two distributions for each assay. RESULTS: The s/co ratio distributions for BFR and confirmed results overlapped in the range of 10.00 to 60.00, 1.00 to 6.00, 3.00 to 15.00, and 1.00 to 100.00 for the PRISM HIV O Plus, HCV, HTLV‐I/II, and HBsAg assays, respectively. CONCLUSION: Although high s/co ratios were predictive of confirmed‐positive results in all four assays, a number of confirmed‐positive samples gave low values while some biologic false‐positive samples showed high values. As the s/co ratio distributions for BFR and confirmed‐positive results overlapped for all four PRISM assays, this study highlights the importance of serologic confirmatory testing and the need for caution when using screening IA results to assign a final donor status.     

Evidence for persistent hepatitis C virus (HCV) infection in hemophiliacs.

Hepatitis C virus (HCV) is the major etiologic agent associated with non-A, non-B hepatitis. This study was designed to assess virologic and serologic markers in hemophiliacs exposed to non-heat-treated and/or virus-inactivated plasma derivatives. Serial bleeds from 48 hemophilic patients were analyzed for the presence of HCV viral RNA sequences as detected by polymerase chain reaction (PCR) and antibodies to structural (core) and nonstructural (C-100 and 33C) proteins by specific dot immunoblot assay. All patients exposed to non-heat-treated products, and four of six patients exposed only to virus inactivated products, had evidence of HCV infection. However, over the 5-yr study period, six exposed patients (13%) consistently lacked detectable anti-C-100 and seven (15%) lost this antibody. HCV viremia (PCR positive) was found in 91% of exposed patients, and was significantly more frequent in HIV seropositive hemophiliacs (P less than 0.05). Six patients had high antibody level to HCV and elevated ALT, but appeared to clear viremia. Four hemophiliacs were HCV seropositive but lacked detectable viremia. These data indicate that hemophiliacs remain persistently infected by HCV and that antibody to the core antigen of HCV is a reliable marker of this transfusion transmissible agent.     

Laboratory evaluation of rapid test kits to detect hepatitis C antibody for use in predonation screening in emergency settings

BACKGROUND: Emergency whole blood transfusion is a lifesaving procedure employed on modern battlefields. Rapid device tests (RDTs) are frequently used to mitigate transfusion‐transmitted infection risks. STUDY DESIGN AND METHODS: A limited evaluation of the RDT formerly used on battlefields was performed using 50 donor plasma samples and commercially available panels. Five hepatitis C virus (HCV) RDTs with sufficient stated sensitivity and thermostability were assessed using 335 HCV‐positive and 339 HCV‐negative donor plasma samples, 54 seroconversion panel plasma samples, and 84 HCV‐positive and 84 HCV‐negative spiked whole blood under normal, hot, and cold storage conditions and normal and hot test conditions, plus an ease‐of‐use survey. RESULTS: BioRapid HCV test sensitivity on donor plasma was 84% (95% confidence interval [CI], 70.9%‐92.8%). Using all positive plasma samples, OraQuick HCV sensitivity exceeded all comparators (99.4%, 95% CI, 98.0%‐99.9%, p < 0.05). Specificity was consistently high, led by OraQuick HCV at 99.7% (95% CI, 98.6%‐100%), statistically superior only to Axiom HCV (p < 0.05). Using seroconversion panels, only OraQuick HCV showed equivalent or earlier HCV detection compared to the gold standard. Using spiked whole blood, specificity was consistently high, and sensitivity ranged significantly from 34.5% (95% CI, 25.0%‐45.1%) for CORE HCV to 98.8% (95% CI, 94.3%‐99.9%) for OraQuick HCV. All comparator RDTs were significantly less sensitive than OraQuick HCV at one or more stress condition. CONCLUSION: This HCV RDT comparison identified significant sensitivity differences, particularly using whole blood under extreme storage and testing conditions. These data support OraQuick HCV superiority and illustrate the value of RDT evaluation under simulated field conditions.     

Risk factor analysis of hepatitis C virus infection among Chinese blood donors in Hong Kong

Background: Hepatitis C virus (HCV) infection can result in serious hepatic complications and hence potentially significant burden to the society. Despite advances in technology, transfusion‐transmitted HCV infection still exists. To further minimise the risk, a review on the epidemiology of HCV infection among Chinese blood donors in Hong Kong was conducted. Methods: All donations associated with HCV infection confirmed by positive serologic diagnosis with or without molecular confirmation during the period from 2003 to 2010 were studied. Demographic data were retrieved and risk factors were identified. Results: HCV infection was more commonly seen in first time donors and donors with blood transfusion history before the availability of HCV testing, whereas its association with intravenous drug use was noted to be decreasing. Interestingly, half of the HCV positive donors in 2008–2010 were young donors aged below 21, which was also the group with the highest rate of no known source of infection. Conclusion: A subgroup of younger age donors was found to have no known risk factor. To develop better screening strategy, it is recommended that a more detailed analysis of this group of donors is required.     

Trypanosoma cruzi infection in North America and Spain: evidence in support of transfusion transmission (CME)

BACKGROUND: The United States, Canada, and Spain perform selective testing of blood donors for Trypanosoma cruzi infection (Chagas disease) to prevent transfusion transmission. The donor, product, and patient characteristics associated with transfusion‐transmitted infections are reviewed and the infectivity of components from donors with serologic evidence of infection is estimated. STUDY DESIGN AND METHODS: A systematic review of transfusion‐transmitted T. cruzi cases and recipient tracing undertaken in North America and Spain is described. Cases were assessed for the imputability of the evidence for transfusion transmission. RESULTS: T. cruzi infection in 20 transfusion recipients was linked to 18 serologically confirmed donors between 1987 and 2011, including 11 identified only by recipient tracing. Cases were geographically widely distributed and were not associated with incident or autochthonous infections. Index clinical cases were described only in immunocompromised patients. All definite transmissions (n = 11) implicated apheresis or whole blood–derived platelets (PLTs), including leukoreduced and irradiated products. There is no evidence of transmission by red blood cells (RBCs) or frozen products, while transmission by whole blood transfusion remains a possibility. Recipient tracing reveals low component infectivity from serologically confirmed, infected donors of 1.7% (95% confidence interval [CI], 0.7%‐3.5%) overall: 13.3% (95% CI, 5.6%‐25.7%) for PLTs, 0.0% (95% CI, 0.0%‐1.5%) for RBCs, and 0.0% (95% CI, 0%‐3.7%) for plasma and cryoprecipitate. CONCLUSIONS: T. cruzi is transmitted by PLT components from some donors with serologic evidence of infection. Evidence of transmission before the implementation of widespread testing in the countries studied is sparse, and selective testing of only PLT and fresh whole blood donations should be considered.     

Dynamics of viremia in early hepatitis C virus infection

BACKGROUND: It is important to characterize viral dynamics in early hepatitis C virus (HCV) infection to further our understanding of viral pathogenesis and the potential for secondary transmission in acute infection through blood transfusion or other routes. STUDY DESIGN AND METHODS: Serial units given by 77 source plasma donors who had evolved from HCV RNA-negative to HCV RNA-positive by nucleic acid amplification technology (NAT) screening with 512-unit pool-NAT or were followed from RNA detection to antibody conversion were tested by individual NAT and quantitative RNA assays. RESULTS: During the ramp-up phase when exponential growth occurs, HCV viral load doubled every 10.8 hours (95% confidence interval [CI], 9.9-12.0). Intermittent viremia was observed before the ramp-up phase in 37 of 50 panels with the earliest detectable viremic bleed occurring 63 days before the estimated onset of ramp-up. The plateau phase or high-titer viremic period that occurs between ramp-up and seroconversion was estimated to last 56.3 days (95% CI, 44.8-67.8). CONCLUSIONS: Intermittent low-level HCV viremia can occur as much as 2 months before the periods of exponential increase in viral load and the high-titer plateau-phase viremia that usually precede seroconversion. Animal inoculation studies are in progress to evaluate if transfusion of low-level viremic plasma can transmit HCV infection.