Hepatitis B surface antigen levels: association with 5-year response to peginterferon alfa-2a in hepatitis B e-antigen-negative patients.

PURPOSE: To investigate the durability of response to peginterferon alfa-2a up to 5 years post-treatment and factors associated with response in hepatitis B e-antigen (HBeAg)-negative patients. METHODS: HBeAg-negative patients received peginterferon alfa-2a (180 µg/week) ± lamivudine (100 mg/day) for 48 weeks as part of a multicenter, randomized study. The planned 5-year efficacy analysis included patients (n = 230) enrolled in the long-term follow-up study. On-treatment hepatitis B surface antigen (HBsAg) decline kinetics were analyzed retrospectively in a subgroup of patients with HBsAg data available at baseline, weeks 12, 24, and 48 on-treatment, and 6 months post-treatment (n = 120). Receiver operating characteristic analyses identified the on-treatment HBsAg levels associated with response at 1 and 5 years post-treatment. RESULTS: HBV DNA ≤2,000 IU/mL and HBsAg clearance at 5 years post-treatment were achieved by 23 and 12% of patients, respectively. High rates of HBsAg clearance at 5 years post-treatment were achieved by patients with HBV DNA ≤2,000 IU/mL at 1 year post-treatment (28%). Rates of HBV DNA ≤2,000 IU/mL at 1 year post-treatment were 47.2 and 43.4% in patients with ≥10% decline from baseline at weeks 12 and 24, respectively, compared with 16.4% (p = 0.0003) and 13.2% (p < 0.0004) in patients with a <10% decline. Rates of HBsAg clearance at 5 years post-treatment were 22.6 and 22.4% in patients with ≥10% decline at weeks 12 and 24, respectively, compared with 7.5% (p = 0.0161) and 3.8% (p < 0.0001) in patients with <10% decline. CONCLUSIONS: Peginterferon alfa-2a results in increasing rates of HBsAg clearance during post-treatment follow-up in HBeAg-negative patients. On-treatment decline in HBsAg is significantly associated with long-term post-treatment response.

Hepatitis B surface antigen: association with sustained response to peginterferon alfa-2a in hepatitis B e antigen-positive patients.

PURPOSE: Patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B, who achieve HBeAg seroconversion 6 months after completing 48 weeks of peginterferon alfa-2a therapy, have an increased chance of clearing hepatitis B surface antigen (HBsAg) during long-term treatment-free follow-up. This analysis aimed to determine whether HBsAg quantification during treatment could be used to identify posttreatment response. METHODS: Patients (n = 399) treated with peginterferon alfa-2a (180 µg/week) alone or in combination with lamivudine (100 mg/day) for 48 weeks during a large, randomized study were included in this retrospective analysis. Receiver-operating characteristic analyses were used to identify baseline and on-treatment HBsAg levels associated with response (HBeAg seroconversion 6 months posttreatment). RESULTS: Baseline HBsAg levels were lower in patients achieving posttreatment response than in nonresponders (3.97 and 4.21 IU/mL, respectively, p = 0.039). Two baseline HBsAg cutoff levels (5,000 and 50,000 IU/mL) provided a positive predictive value of 42% and a negative predictive value of 77%. HBsAg decline was significantly greater during and posttreatment in responders than in nonresponders (p < 0.0001). HBeAg seroconversion rates 6 months posttreatment were significantly higher in patients with HBsAg < 1,500 IU/mL at weeks 12 and 24 (56.7 and 54.4%, respectively) versus patients with HBsAg 1,500-20,000 IU/mL (32.3 and 26.1%, respectively) or HBsAg < 20,000 IU/mL (16.3 and 15.4%, respectively) (all p < 0.0001 and <0.0001). CONCLUSIONS: HBsAg levels at baseline strongly associated with posttreatment response were not identified. Low HBsAg levels during peginterferon alfa-2a therapy were associated with high rates of posttreatment response. On-treatment HBsAg quantification may, therefore, help guide patient management in the future.

HBsAg blood screening and diagnosis: performance evaluation of the ARCHITECT HBsAg qualitative and ARCHITECT HBsAg qualitative confirmatory assays.

A low initial reactive rate for screening assays is important for time- and cost-effective infectious disease testing. Therefore, the new ARCHITECT HBsAg Qualitative screening assay, in conjunction with the new ARCHITECT HBsAg Qualitative Confirmatory assay, was introduced. As the role of hepatitis B surface antigen (HBsAg) as surrogate marker for HBV resolution and the monitoring of drug effectiveness are becoming increasingly important, the established ARCHITECT HBsAg Quantitative assay remains available on the market. Precision, sensitivity, and specificity of the newly developed screening assay were in the range of established HBsAg assays. Seroconversion sensitivity was slightly superior compared to other commercially available assays. An initial reactive rate of 0.2% (without HBsAg-confirmed positive samples of 0.17%) for the ARCHITECT HBsAg Qualitative assay was observed. As the new screening assay is a 1-step assay format, the "high-dose hook effect" was investigated to assess the risk of false-negative results, but even very high positive HBsAg samples obtained signals clearly above the cutoff.

Development of a fluorescence resonance energy transfer peptide library technology for detection of protease contaminants in protein-based raw materials used in diagnostic assays.

Protease impurities in raw materials used in enzyme immunoassays can impair assay performance. This risk may be greatly decreased if incoming protein-based raw materials are controlled for protease impurities or if protease inhibitors are used in the assay formulations. As many different proteases might occur in protein raw materials, it is desirable to have a general test for protease contamination. With the help of a fluorescence resonance energy transfer peptide library containing about 2.5 million peptides, we have succeeded in establishing such a system, with sensitivity in the nanogram range for known proteases. Protease contamination was found to differ between different raw materials and was correlated with assay performance. Protease activity in contaminated raw materials could be suppressed to various degrees with different chemical inhibitors or by thermal treatment. This technology is suited for the control of incoming protein-based raw materials used for enzyme immunoassays, as well as for the optimization of the use of protein inhibitors or thermal treatment of protein-based raw materials for the inactivation of proteases.

Evaluation of a new third-generation ARCHITECT rHTLV-I/II assay for blood screening and diagnosis.

In comparison to current on-market assays, the ARCHITECT rHTLV-I/II assay is the first fully automated assay that simultaneously detects human T-cell lymphotropic virus type I (HTLV-I) and type II (HTLV-II) in human serum and plasma. Specificity was assessed on 5646 blood donors and 692 clinical specimens. For sensitivity determination, 301 HTLV-I-positive and 105 HTLV-II-positive specimens were tested. Precision was between 3.98% and 4.31% coefficient of variation (CV) for specimens with 1 to 6 sample to cutoff. Specificity was 99.95% and 99.86% on specimens from blood donors and hospitalized patients, respectively. Sensitivity evaluation showed 100% detection on 301 HTLV-I and 105 HTLV-II specimens. HTLV-I and HTLV-II viruses are still circulating among general populations even in the low prevalence areas. To control the further spread of these retroviruses, we need to know that it is important to continue screening of blood. The performance evaluation data from this study demonstrate that the high throughput and fully automated ARCHITECT rHTLV-I/II chemiluminescence immunoassay effectively serves this purpose.

Performance evaluation of the new fully automated human immunodeficiency virus antigen-antibody combination assay designed for blood screening.

BACKGROUND: Before the introduction of human immunodeficiency virus (HIV) combination assays, serologic diagnosis of HIV infection was performed with assays that detected either antibodies or p24 antigen. Owing to the capability to detect the early appearance of p24 antigen, combination assays that are designed for simultaneous detection of antibodies and antigen can significantly reduce the diagnostic window. STUDY DESIGN AND METHODS: Specificity and sensitivity of a commercially available HIV antigen-antibody combination assay (Abbott PRISM; assay is not licensed by the FDA for use in the United States) were evaluated in a multicenter study by testing volunteer blood donors, hospitalized patients, seroconversion panels, and p24 antigen and HIV antibody subtype panels. Performance data were compared to a commercially available HIV combination assay and the PRISM HIV O Plus assay. RESULTS: Apparent specificity of 99.95 percent was observed in the donor population for the PRISM HIV antigen-antibody combination assay, and better seroconversion sensitivity was demonstrated compared with another combination assay and the PRISM HIV O Plus assay. Analytical HIV antigen detection sensitivity averaged 33 pg per mL on the Agence Française de Sécurité Sanitaire des Produits de Santé (AFSSAPS) panel. Furthermore, comparable antigen sensitivity was demonstrated for 32 HIV-1 group M subtype and group O panels. The PRISM HIV combination assay detected all HIV-1 group M and O and HIV-2 antibody-positive specimens evaluated. CONCLUSIONS: The PRISM HIV antigen-antibody combination assay demonstrated a significant reduction of the window period for diagnosis of HIV infection. The assay demonstrated enhanced specificity and sensitivity along with broad subtype detection. The assay performance represents the "state-of-the art" technology for serologic blood screening of HIV infection.

Sensitivity of a modified version of the ARCHITECT Anti-HCV test in detecting samples with immunoblot-confirmed, low-level antibody to hepatitis C virus.

BACKGROUND AND OBJECTIVES: Compliance with current regulations regarding the prevention of hepatitis C virus (HCV) transmission in the blood transfusion setting requires the use of sensitive assays for HCV antibody (anti-HCV) detection, which should, ideally, identify any donor having had prior contact with the virus. Therefore, low-level anti-HCV positive blood units should be detected by the screening assays, even those reflecting a past and resolved infection. To assess the sensitivity of two versions of an automated chemiluminescent microparticle immunoassay (CMIA) for anti-HCV screening (ARCHITECT Anti-HCV), 113 single serum samples containing low levels of anti-HCV, assessed by two immunoblot tests, were selected from 3686 samples received for confirmation of HCV infection by a reference laboratory over a 2-year period. MATERIALS AND METHODS: The panel included 17 samples with HCV RNA detected by the polymerase chain reaction (PCR) and 96 PCR negative samples with either positive or indeterminate (anti-Core and anti-NS3 alone) results by immunoblot. RESULTS: All but 13 specimens (100/113, 88.5%) were detected by the current version of the ARCHITECT Anti-HCV assay and 10 additional samples (110/113, 97.3%) tested positive in a modified version of the test. CONCLUSION: The results showed that the modification introduced in the ARCHITECT Anti-HCV assay achieves a significant sensitivity improvement including samples with low-level anti-HCV which are either PCR positive or negative.

Performance characteristics of the ARCHITECT anti-HCV assay.

INTRODUCTION: The ARCHITECT Anti-HCV assay is a fully automated high throughput chemiluminescent microparticle immunoassay (CMIA) for the detection of antibodies to structural and nonstructural proteins of the hepatitis C virus (HCV). To further enhance the performance of this test, the assay was modified to improve the specificity for blood donor specimens. METHODS: The specificity of the enhanced ARCHITECT Anti-HCV assay was evaluated by screening blood donor samples randomly collected from various German blood banks, as well as hospitalized patient samples derived from Germany and the US. Additionally, antibody sensitivity was determined on commercially available anti-HCV seroconversion panels and on a commercially available worldwide anti-HCV genotype performance panel. RESULTS: Apparent specificity of the modified ARCHITECT Anti-HCV assay in a blood donor population consisting of 3811 specimens was 99.92%, compared to 99.76% for the current on-market assay. Additionally, antibody sensitivity was determined on commercially available anti-HCV seroconversion panels. Seroconversion sensitivity equivalent to or better than the current on-market product was observed by testing 33 seroconversion panels. CONCLUSION: This study demonstrates that the modified version of the ARCHITECT Anti-HCV assay shows improved specificity for blood donor specimens compared to the current assay on market without compromising sensitivity. With the availability of the improved ARCHITECT Anti-HCV assay and the recent launch of the ARCHITECT HIV Ag/Ab Combo assay, the ARCHITECT system now offers a full hepatitis/retrovirus menu with excellent performance on a high throughput, random access, automated analyzer, ideally suited for blood screening and diagnostic applications.

Multicenter evaluation of a new, automated enzyme-linked immunoassay for detection of human immunodeficiency virus-specific antibodies and antigen.

A collaborative multicenter study was conducted to evaluate the sensitivity, specificity, and precision of a three-step, fully automated, qualitative microparticle-based enzyme-linked immunoassay (AxSYM HIV Ag/Ab Combo; Abbott Laboratories), designed to simultaneously detect (i). antibodies against human immunodeficiency virus type 1 (HIV-1) and/or type 2 (HIV-2) and (ii). HIV p24 antigen. A significant reduction in the HIV seroconversion window was achieved by combining detection of HIV antibodies and antigen into a single assay format. For 22 selected, commercial HIV seroconversion panels, the mean time of detection with the combined-format HIV antigen-antibody assay was reduced by 6.15 days compared to that with a similar third-generation single-format HIV antibody assay. The quantitative sensitivity of the combination assay for the p24 antigen (17.5 pg/ml by use of the p24 quantitative panel VIH SFTS96') was nearly equivalent to that of single-format antigen tests. The combination assay demonstrated sensitive (100%) detection of anti-HIV immunoglobulin in specimens from individuals in CDC stages A, B, and C and from individuals infected with different HIV-1 group M subtypes, group O, or HIV-2. The apparent specificity for hospitalized patients (n = 1938) was 99.90%. In a random population of 7900 volunteer blood donors, the specificity (99.87%) was comparable to that of a third-generation single-format HIV antibody assay (99.92%) on the same donor specimens. In addition, the combination assay was robust to potential interfering specimens. The precision of the combination was high, with intra- and interrun variances of