Comparison of enzyme immunoassay with radioimmunoassay for the detection of antibody to hepatitis B core antigen as the only marker of hepatitis B infection in a population with a high prevalence of hepatitis B

An innovative wireless electrochemical card sensor for field-deployable diagnostics of Hepatitis B surface antigen

A wireless-based detection utilizing an innovative electrochemical card (eCard) sensor controlled by a smartphone was developed for targeting Hepatitis B surface antigen (HBsAg). A simple label-free electrochemical platform allows a convenient operation for point-of-care diagnosis. A disposable screen-printed carbon electrode was modified straightforwardly layer-by-layer with chitosan followed by glutaraldehyde, allowing a simple but effective, reproducible, and stable method for covalently immobilizing antibodies. The modification and immobilization processes were verified by electrochemical impedance spectroscopy and cyclic voltammetry. The smartphone-based eCard sensor was used to quantify HBsAg by measuring the change in current response of the [Fe(CN)₆]^3-/4- redox couple before and after the presence of HBsAg. Under the optimal conditions, the linear calibration curve for HBsAg was found to be 10-100,000 IU/mL with a detection limit of 9.55 IU/mL. The HBsAg eCard sensor was successfully applied to detect 500 chronic HBV-infected serum samples with satisfactory results, demonstrating the excellent applicability of this system. The sensitivity and specificity of this sensing platform were found to be 97.75% and 93%, respectively. As illustrated, the proposed eCard immunosensor offered a rapid, sensitive, selective, and easy-to-use platform for healthcare providers to rapidly determine the infection status of HBV patients.

Universal infant immunization and occult hepatitis B virus infection in children and adolescents: a population-based study

To determine whether universal infant immunization affects occult hepatitis B virus (HBV) infection (OBI), serum samples from hepatitis B surface antigen (HBsAg)-negative subjects <18 years enrolled during six sequential seroepidemiological surveys conducted between 1984 (just before universal infant immunization) and 2009 were analyzed. Study subjects were divided into unvaccinated cohorts (born before 1984) and vaccinated cohorts (born after 1984). HBV-DNA positivity was determined by positivity of nested polymerase chain reaction in at least two of three regions (pre-S, S, and pre-core/core genes). OBI frequency was lower in vaccinated than unvaccinated antibody to hepatitis B core antigen (anti-HBc)-negative subjects (0 of 392 [0%] vs. 4 of 218 [1.8%]; P = 0.007), tended to be higher in vaccinated than unvaccinated anti-HBc-positive subjects (16 of 334 [4.8%] vs. 3 of 181 [1.7%]; P = 0.072), and was higher in vaccinated than unvaccinated subjects seropositive for both antibody to hepatitis B surface antigen (anti-HBs) and anti-HBc (13 of 233 [5.6%] vs. 3 of 170 [1.8%]; P = 0.025). By using known anti-HBc seropositivity rate in children in our serosurveys, the estimated OBI frequency per 10(4) HBsAg-negative subjects declined from 160.7 in unvaccinated cohorts to 11.5 in vaccinated cohorts. In vaccinated cohorts, OBI frequency was higher in anti-HBc-positive subjects than in anti-HBc-negative subjects (16 of 334 [4.8%] vs. 0 of 392 [0%]; P < 0.001). Subjects with OBI had much lower viral load (P < 0.001) and a trend of higher mutation rates in "a" determinant of HBsAg than age-comparable, HBsAg-positive subjects.

CONCLUSIONS

Reduction of OBI in immunized subjects complements the well-documented universal infant immunization-related benefit of markedly reduced overt HBV infection. Breakthrough infections in immunized subjects seem to associate with more occurrence of OBI than natural infections in unvaccinated subjects. In the postvaccination era, anti-HBc seropositivity is a useful marker for OBI screening in HBsAg-negative subjects, and a very-low-level viral replication and HBsAg expression is the major mechanism underlying OBI.

Presence of low levels of anti-HBs antibody in so-called 'anti-HBc alone' subjects

BACKGROUND/AIMS

The 'anti-Hbc alone' pattern could sometimes be that of subjects who produced anti-HBs after recovery, but at a lower level than that detectable using commercial assays. This study aimed to test this hypothesis.

METHODS

A total of 104 'anti-HBc alone' serum samples, i.e.positive for the anti-HBc antibody but not for HBsAg nor for anti-HBs antibody, were recruited when routine testing a broad population of employees, patients and pregnant women from a university hospital. A possible subliminal anti-HBs production, that would have escaped detection by commercial EIAs, was investigated by comparing the optical densities (ODs) obtained in vaccinees (commercial anti-HBs EIA) to those of a control group of 100 nonimmunised and nonvaccinated subjects.

RESULTS

The median OD was significantly higher (p<0.0001) in the 'anti-HBc alone' subjects (OD=0.035) than in the controls (OD=0.023). Thirty-six percent of the 'anti-HBc alone' subjects had an anti-HBs OD higher than the median OD of the controls+2SD. 'Anti-HBc alone' subjects with anti-HBe antibody had higher anti-HBs ODs (0.041) than had those without anti-HBe (0.029). In 'anti-HBc alone' subjects, the anti-HBs ODs, although under the cut-off value of the EIA, were found to be higher than in the controls.

CONCLUSION

Our results show low anti-HBs production in some of the subjects studied.

Significance of isolated hepatitis B core antibody in blood donors from São Paulo

The clinical significance of isolated anti-HBc is still a challenge. To elucidate the real importance of this finding in our blood donors, an investigation algorithm was tested. One hundred and twelve isolated anti-HBc seropositive blood donors underwent clinical evaluation and retesting of HBV markers. Those who presented repeatedly reactive isolated anti-HBc, received a single dose of hepatitis B recombinant vaccine to verify anti-HBs early response. A HBV-DNA determination by PCR was done for those who did not test positive to anti-HBs after vaccine. The level of anti-HBc was recorded as a ratio of the sample-to-cut-off values (S:C ratio) in 57 candidates at donation. Comparing true and false-positive anti-HBc results, the different S:C ratios of them were statistically significant and when less than 2, implying in a false-positive result probability over 80%. A high percent of false-positive results (16.07%) was verified after anti-HBc retesting. HBV immunity was characterized in 49.11%, either by anti-HBs detection in retesting (15.18%), or after a single dose HBV vaccination (33.93%). HBV-DNA was negative in all tested donors. In conclusion, this algorithm was useful to clarify the meaning of isolated anti-HBc in most of our blood donors.

Prevalence of hepatitis A virus and hepatitis B virus immunity in patients with polymerase chain reaction-confirmed hepatitis C: implications for vaccination strategy

OBJECTIVES

Administration of vaccine for hepatitis A virus (HAV) and hepatitis B virus (HBV) is recommended for patients with chronic hepatitis C (CHC) because of the potential for increased severity of acute hepatitis superimposed on existing liver disease. The aim of this study is to determine the prevalence of antibodies directed against HAV and HBV in patients with CHC, analyze demographic and risk factors associated with this prevalence, and develop a cost-effective vaccination strategy.

METHODS

We reviewed records from 1092 CHC patients. Demographics and information regarding risk factors were obtained by history and questionnaire administered to all patients. The costs of vaccination and antibody testing were determined, based on standard laboratory and clinic charges at our institution. HAV and HBV markers were correlated to race, age, and risk factors.

RESULTS

Of the total population studied (n = 1092), 72% were African-Americans, 27% white, and 1% others. Of 671 CHC patients tested for anti-HAV IgG, 252 (38%) were positive. Of 743 CHC patients tested for HBV antibodies (anti-hepatitis B core IgG or anti-hepatitis B surface), 494 (67%) were positive. African-Americans are more likely to have antibodies to HAV and HBV (67% and 75%, respectively) compared to whites (27% and 20%). The prevalence of anti-HAV was 76% in patients >60 yr, 34% in the 40- to 60-yr-old age group, and 21% in patients <40 yr. The highest prevalence of HBV antibodies was found in patients between the ages of 40-60 yr. No HCV risk factors were associated with increased HAV risk. In CHC patients with HBV antibodies, however, illicit injection drug use was the predominant risk factor.

CONCLUSIONS

The prevalence of anti-HAV in patients with CHC was found to be similar to that of the general population in the United States (33% according to recent Centers for Disease Control data), consistent with the hypothesis that the two infections do not share risk factors. Because the prevalence of HAV immunity is low in CHC patients <40 yr, empiric HAV vaccination is cost effective. If two doses of vaccine are to be given, however, antibody testing of all HCV patients is indicated. In the subset of patients >60 yr of age or who are African-American, where the prevalence of HAV exposure is considerably higher, it would be cost effective to check the antibody ($36.00), before vaccination ($97.00). The prevalence of HBV antibodies, however, is significantly increased in patients with CHC compared with the general population (5.3% per the Centers for Disease Control), likely as a result of exposure to similar parenteral risk factors. HBV antibody testing ($26.00 per test) should, therefore, be undertaken in all CHC patients who are hepatitis B surface antigen negative, as this approach is cost-effective compared to empiric HBV vaccination ($438.00 for a three injection course).

Hepatitis B core antibody screening in a high prevalence group: comparison of three enzyme immunoassays using receiver operating characteristic analysis

Selected sera from 296 homosexual men were screened by 3 commercially available anti-HBc enzyme immunoassays (EIA). All patients could be classified either as non-immune to hepatitis B, or with current or previous hepatitis B infection. Using the cut-off optical density values (O.D. values) recommended by the respective manufacturers, the results from these three assays were identical for 83% of the serum samples. For anti-HBc reactivity, the ratio (percentage) was calculated using O.D. sample x 100 divided by the O.D. cut-off value. Employing these ratios, sensitivities and specificities for the three assays were compared. All assays performed well when analyzed by receiver operating characteristic curves with area under the curves of 96-97%. A higher specificity, with only a marginal loss of sensitivity could be achieved by lowering the cut-off to 55% for the Enzygost EIA, to 85% for the Enzygost-monoclonal EIA and to 60% for the Corzyme EIA. Using the modified cut-off values, the results with the three assays agreed for 93% of the serum samples.

A multicentre assessment of the specificity of ten anti-HBc screening tests

Samples from 1828 donations were screened for anti-HBc at seven sites in the UK using kits supplied by 10 manufacturers. Only 10 (0.55%) donations were considered to have true anti-HBc reactivity and these were detected by all 10 kits. Additional markers of HBV infection were found in nine of these 10 donations. Additional reactives were found by all kits, the number ranging from 1 to 43. In the four more specific kits, the 10 true reactives were clearly distinguished from the 'false reactives' by the strength of the reaction. It is concluded that the reliance on a single ELISA test for anti-HBc diagnosis is unwise. The use of a second test known to be more specific than the screening ELISA is recommended.

Prevalence and risk factors for HBV infection among street youth in central Brazil

PURPOSE

A seroprevalence survey was carried out among 496 street adolescents from 9 to 20 years old in central Brazil to determine the prevalence of hepatitis B (HBV) markers, as well as to assess the role of potential risk factors.

RESULTS

The findings reveal that 20.4% of the participants were homeless adolescents without family links, living and/or working on the streets. The age at first sexual intercourse was as low as 9 years old, and approximately 60% of this population had had at least one sexual relationship by the age of thirteen, indicating prepubertal initiation of sexual experiences among street adolescents. 13.5% were HBV marker-positive (anti-HBc) and 2.0% had antigenemia. Street-based youth had a higher HBV marker-positive rate when compared to home-based teens (OR = 4.1, 95% CI: 2.1-8.5) and, similarly, higher HBV prevalence was obtained for those reporting sexual activity versus the group without sexual activity (OR = 2.1, 95% CI: 1.1-3.9), even after adjusting for potential confounders.

CONCLUSIONS

We have found that street youth, particularly street-based adolescents, should be considered at-risk group for hepatitis B infection in our region. These findings may be used as a baseline information for policy changes not only in hepatitis B prevention but also to reverse the scenario of adolescents sexual abuse.

Presence of hepatitis B and C viral genomes in US blood donors as detected by polymerase chain reaction amplification

Hepatitis C virus (HCV) represents a major cause of posttransfusion hepatitis worldwide. Posttransfusion hepatitis associated with hepatitis B virus (HBV) continues to occur. HBsAg-negative donor sera from the Rhode Island Blood Center between 1987 and 1988 were screened using more sensitive techniques to assess the prevalence of low level HBV infection. Group I consists of 866 healthy blood donors without HBV serologic markers, group II consists of 377 donors with ALT elevations (> 45 IU/L), group II consists of 148 donors positive for anti-HBc, and group IV consists of eight donors positive for both surrogate markers. A sensitive monoclonal immunoradiometric assay (M-IRMA) was employed for detection of HBsAg-associated epitopes (detection limit of 20 pg/ml) in serum. A subset of sera were analyzed for the presence of HBV DNA using the method of anti-HBs capture of HBV related virions in serum followed by polymerase chain reaction (PCR) amplification. Using these techniques, 0.8% and 1.7% of donors were positive for HBsAg and HBV DNA respectively in group I. In contrast, 0.9% and 9.5% in group II and 0.7% and 18.1% in group III were positive, respectively. There were eight donors with both ALT elevation and anti-HBc; and four (50%) of these were positive for HBV DNA. In the group with anti-HBc, the majority (80%) of donors with HBV DNA had either no or low (signal to noise ratio < 10) anti-HBs titer. Using anti-HCV testing and reverse transcription-PCR for detection of HCV genomes, we detected evidence of HCV infection in nine of the 49 donors with low level HBV DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of former and newly developed HBV assays in a Third World setting

Newly available HBV serological assays have not been established routinely in most underdeveloped countries. Utilizing enzyme-immune assays to determine the presence of pre-S1 antigen and anti-pre-S2, and using two conventional hybridization techniques and the PCR assay to detect HBV-DNA, we studied 30 HBsAg chronic carriers and as a reference group 10 subjects whose only HBV routine marker was anti-HBc. Seventy-nine percent of the HBeAg positive carriers showed detectable HBV-DNA by a non-radioactive slot-blotting technique. The PCR assay was more sensitive than the slot-blotting technique, detecting HBV-DNA in anti-HBe positive patients with moderate or normal ALT activity. Pre-S1 antigen was mostly related to the presence of HBsAg and anti-pre-S2 was associated with active viremic state, increased ALT activity (ranges 51 to 640 IU/L), and with self-limited HBV infection. The presence of HBV-DNA in the group with anti-HBc only was detectable solely by the PCR assay. For an underdeveloped country the addition of a PCR assay or pre-S/anti-pre-S protein tests to the current assessment procedures of HBV chronic infection should be used only in selective cases. HBeAg/anti-HBe serological evaluation and HBV-DNA detection by a non-isotopic conventional hybridization technique still remain as useful tools to screen initially for the presence of viremia in chronic HBsAg carriers. The presence of HBV-DNA in individuals with anti-HBc only suggests that anti-HBc screening should be maintained and expanded to all the blood banks of less industrialized countries where the rate of HBV infection in apparently healthy people tends to be high.

Response to hepatitis B vaccine of persons positive for antibody to hepatitis B core antigen

The significance of antibody to hepatitis B core antigen (anti-HBc) present in a person's serum without hepatitis B surface antigen (HBsAg) or its antibody (anti-HBs) is unknown. Serum specimens from 281 persons initially positive only for anti-HBc by enzyme immunoassay (EIA) were retested by radioimmunoassay (RIA), and of these, 177 (63%) remained positive for anti-HBc by both assays. Of these 177 persons, 3 were positive for HBsAg, and 72 possessed low levels of anti-HBs [less than 10 sample ratio units; (SRU's)]. When persons positive for anti-HBc by EIA and RIA were given one 20-micrograms dose of plasma-derived hepatitis B vaccine and tested for anti-HBs 1 month later, a booster response was observed in 14 of 41 (34%) persons with low level anti-HBs and 3 of 50 (6%) persons negative for anti-HBs. Of those positive only for anti-HBc by EIA but negative by RIA, only 3 of 37 (8.1%) showed a booster response. Of those who completed the three-dose immunization series and did not show a booster response, 63 of 80 (78.8%) developed anti-HBs levels greater than 10 standard ratio unit. The majority of persons with isolated anti-HBc will have a primary rather than a booster response to hepatitis B vaccine.

Significance of isolated hepatitis B core antibodies detected by enzyme immunoassay in a high risk population

Serum samples, which were found positive for anti-HBc and negative for HBsAg and anti-HBs during routine testing with Abbott enzyme immunoassays (EIA), were collected prospectively. The samples were obtained from patients with a high risk of hepatitis B. Further analysis was carried out using radioimmunoassays and tests for additional markers of hepatitis B. 84 of the 203 initially collected samples (41.4%) were found positive for anti-HBs by RIA. Of the 119 samples negative for anti-HBs by RIA, 103 were available for further investigation, and 35 (34.0%) of these were negative for anti-HBc by RIA. This indicates that low sensitivity of the anti-HBs EIA and non-specificity of the anti-HBc EIA may account for about 60% of the cases presenting with isolated anti-HBc at initial testing. Fifty-two samples positive for anti-HBc by RIA, with isolated anti-HBc confirmed after RIA testing for HBsAg and anti-HBs, were examined further: anti-HBe was detected in 16 sera, anti-HDV in one serum and HBV-DNA in 5 sera by PCR. Additional testing of serum samples with isolated anti-HBc is warranted.