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Annals of Clinical & Laboratory Science 37:256-259 (2007)
© 2007 Association of Clinical Scientists

Comparison of the Abbott Architect i2000 Assay, the Roche Modular Analytics E170 Assay, and an Immunoradiometric Assay for Serum Hepatitis B Virus Markers

Hyunjung Kim1, Eun-Jee Oh1, Mi-Sook Kang1, Sung Hoon Kim2 and Yeon-Joon Park1
1 Departments of Laboratory Medicine and 2 Radiology, College of Medicine, The Catholic University of Korea, Seoul, Korea

Address correspondence to Yeon-Joon Park, M.D., Department of Laboratory Medicine, The Catholic University of Korea, Kangnam St. Mary’s Hospital, 505 Banpo-dong, Seocho-ku, Seoul, 137-701, South Korea; tel 82 2 590 1604; fax 82 2 592 4190; e-mail yjpk{at}catholic.ac.kr.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Serum hepatitis B virus (HBV) markers are the most important data for epidemiological screening and clinical diagnosis of HBV infection, especially in endemic areas. We compared the results of the Roche Modular Analytics E170 assay, the Abbott Architect i2000 assay, and an immunoradiometric assay (IRMA) for HBV surface antigen (HBsAg), anti-HBV surface antigen (anti-HBs), HBV e antigen (HBeAg), and anti-HBV e antigen (anti-HBe). A number of serum samples (264, 263, 224, and 202 for HBsAg, anti-HBs, HBeAg, and anti-HBe, respectively) were studied. For samples giving discrepant results for HBeAg between methods, real-time PCR assays were performed. The concordance rates among the three methods were high for HBsAg (100%) and HBeAg (94.6), but low for anti-HBs (91.6%) and anti-HBe (82.2%). For anti-HBs, which could be measured quantitatively by the Modular E170 and Architect i2000 procedures, discrepant results were observed at low levels of anti-HBs. For anti-HBe, the positive rate was highest with Modular E170 (60.9%) followed by the IRMA kit (54.1%) and Architect i2000 (51.0%). This study shows substantial differences between the assay results by the three methods, which should be taken into account in determinations of serum HBV markers.

Keywords: automated analyzers, hepatitis B viral markers, immunoradiometric assay


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Hepatitis B virus (HBV) infection is a major global public health problem. Of the approximately 2 billion people who have been infected worldwide, more than 350 million are chronic carriers of HBV. Approximately 15 to 40% of infected patients will develop cirrhosis, liver failure, or hepatocellular carcinoma (HCC) [1]. In particular the HBsAg seroprevalence in the Western Pacific (China, South Korea, and Taiwan) ranges between 10 and 12% [2]. Determination of serum HBV markers is crucial for rapid screening and clinical diagnosis of HBV infection, particularly in regions with high prevalence. Recently, automated analyzers, such as Roche Modular Analytics E170 (Modular E170) and Abbott Architect i2000 (Architect i2000) have been developed. However, there are few reports that have assessed the performance of these analyzers. In this study, we compared the test results of HBV serologic markers as measured by an immunoradiometric assay (IRMA), the Modular E170 assay, and the Architect i2000 assay.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Four serologic markers were selected for comparison: HBV surface antigen (HBsAg), anti-HBsAg (anti-HBs), HBV e antigen (HBeAg), and anti-HBeAg (anti-HBe). From July to August 2006, 264, 263, 224, and 202 samples were submitted for routine testing for HBsAg, anti-HBs, HBeAg, and anti-HBe, respectively. Samples were tested using IRMA and two automated immunoassay analyzers (Modular E170, Architect i2000) in parallel.

Measurement of four serum HBV markers.  The IRMA kit (North Institute of Biological Technology, Beijing, China), a solid phase radioimmunoassay kit, was used according to the manufacturer’s instruction. First, serum is incubated with beads coated with monoclonal antibody. After 3 washing steps, the second antibody conjugated with I125 reacts with the analytes fixed on the beads. Radioactivity is measured in counts per min (cpm) using a Packard gamma counter (GMI, Inc., Minneapolis, MN, USA). All four HBV markers are measured by the qualitative method. Where the cpm value of the sample exceeds a cut-off value, the result is positive for HBsAg, anti-HBs, and HBeAg; and where the cpm value of the sample is less than the cut-off value, the result is positive for anti-HBe.

The Modular E170 analyzer (Roche Diagnostics, Mannheim, Germany) uses an electrochemiluminescence immunoassay (ECLIA); serum anti-HBs is determined quantitatively while serum HBsAg, HBeAg, and anti-HBe are determined qualitatively. HBsAg, HBeAg, and anti-HBe are interpreted using the ratio of the sample signal to the cut-off signal (S/CO). Results of anti-HBs with concentration values ≥10 IU/L are positive and the upper detection limit is 1,000 IU/L.

The Architect i2000 analyzer (Abbott Diagnostics, Abbott Park, IL, USA) uses a chemiluminescent microparticle immunoassay (CMIA); serum HBsAg and anti-HBs are determined quantitatively, while serum HBeAg and anti-HBe are determined qualitatively. Positive cut-offs values for HBsAg and anti-HBs are ≥0.05 and ≥10 IU/L, respectively; the upper detection limits for HBsAg and anti-HBs are 250 and 1,000 IU/L, respectively. HBeAg and anti-HBe are interpreted using a ratio of the sample relative light unit (RLU) rate to the cut-off RLU (S/CO).

Real-time polymerase chain reaction.  For samples showing discrepant results for HBeAg among the IRMA and two automated analyzers, a real-time PCR assay was performed using HBV PCR kits (Abbott Diagnostics, Hamburg, Germany) and an ABI PRISM 7000 HT Sequence Detection Systems (Applied Biosystems, Foster City, CA, USA). DNA extraction was performed using the Abbott DNA Sample Preparation System (Abbott Diagnostics, Wiesbaden, Germany) following the manufacturer’s instructions. The prepared DNA samples were stored at –20°C until use.

Statistics.  For comparison of anti-HBs titers by the Modular E170 and Architect i2000 assay, the correlation coefficient was calculated by the Excel 2000 program (Microsoft, Seattle, WA, USA).


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
The concordance rates among the three analyzers were 100%, 91.6%, 94.6%, and 82.2% for HBsAg, anti-HBs, HBeAg, and anti-HBe, respectively (Table 1Go). The positive rates and concordance rates between analyzers are shown in Tables 2Go and 3Go.


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  		Table 1. Comparison of serum HBV marker results among the IRMA kit, Modular E170, and Architect i2000 assays.
 

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  		Table 2. Positive rates of the three methods.
 

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  		Table 3. Concordance rates (%) among the three methods.
 
For anti-HBs, the 22 cases that showed discrepancy among the three analyzers were low in anti-HBs level (<100 IU/L). However, the concordance rate of Modular E170 and Architect i2000 was significantly higher (97.3%) than that of IRMA and Modular E170 (92.4%), or that of IRMA and Architect i2000 (93.5%) (Table 3Go). The correlation between the serum anti-HBs levels measured quantitatively by Modular E170 and Architect i2000 was high (r = 0.918) (Fig. 1Go).


Figure 1
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  		Fig. 1. Comparison of anti-HBs titers obtained with the Modular E170 and Architect i2000 anslyzers.

 
For HBeAg, the concordance rate between the two automated analyzers was higher than for each with the IRMA (Table 3Go). Of 224 samples, 7 were negative only by the IRMA, 2 were positive only by IRMA, and for these 9 cases real time PCR was performed. Six of 9 cases showed positive results in real-time PCR. For these 6 samples, IRMA was positive in only 1, whereas with Modular E170/Architect i2000, 5 gave positive results (Table 4Go). Of the 3 real-time PCR negative samples, IRMA gave 2 negative results and Modular E170/Architect i2000 gave 1 negative result. Concordance rates of IRMA and Modular E170/Architect i2000 assays with real-time PCR were 33.3% (3/9) and 66.6% (6/9), respectively.


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  		Table 4. Cases showing HBeAg and Anti-HBe discrepancies among the three methods.
 
For anti-HBe, the positive rate was highest with Modular E170 (60.9%) followed by IRMA kit (54.1%) and Architect i2000 (51.0%). In 16 cases positive results were obtained only by Modular E170, and 15 of them were HBeAg-positive with all three analyzers.


   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Determination of serum HBV markers is crucial for rapid screening and clinical diagnosis of HBV infection, particularly in regions with high prevalence. However, in determination of serum HBV markers, discrepancies among test results from different types of immunoassay analyzers, which could affect the accuracy of epidemic screening and clinical diagnosis, have been reported [3]. In this study, we compared the results for HBsAg, anti-HBs, HBeAg, and anti-HBe among two automated immunoassay analyzers (Modular E170, Architect i2000) and an IRMA assay.

In determination of HBsAg, the concordance rate of the three methods was 100%, but only Architect i2000 could perform quantitative analysis. This quantitative measurement of HBs titers may be an easy and economical reference for HBV replication, because the change in HBsAg concentration correlates well with the changes in HBeAg and HBV DNA levels [4,5]. Serum anti-HBs is important for confirmation of protective immunity after vaccination and recovery after HBV infection. An anti-HBs concentration >10 IU/L, is considered to be protective against HBV infection [6]. Therefore, low titers of anti-HBs must be accurately determined for evaluating the effect of vaccination and booster injections. Modular E170 and Architect i2000 can perform quantitative analysis, and there was good correlation (r = 0.918, concordance rate = 97.3%) between these two analyzers. These findings are in agreement with another report [3]. For comparison with RIA, Wang et al [7] reported that anti-HBs titers measured by EIA correlated well with the results of RIA. However, inconsistent results have been reported in other studies [3, 8–10]. These differences may be related to the various sources of reagents and to the different HBV vaccines [11].

There are fewer reports comparing serum HBeAg and anti-HBe assays than of HBsAg and anti-HBs assays. HBeAg seroconversion is the short-term goal of antiviral therapy in chronic hepatitis B [12], and the fall of HBeAg levels during early treatment is an important independent predictor of response [13]. In the present study, the concordance rate of HBeAg with the three analyzers was high (94.6%), and it was higher between Modular E170 and Architect i2000 (98.7%) than for each with IRMA. In addition, although the HBV DNA level does not always correlate with the HBeAg level, the concordance rate of HBeAg results from Modular E170/Architect i2000 with the HBV DNA level was higher than that of IRMA. For anti-HBe, the positive rate was highest with the Modular E170 assay, which is consistent with a previous study [3]. Of the 16 cases positive only by Modular E170, 15 were HBeAg-positive with all three analyzers, suggesting false positive results with the Modular E170 assay.

In conclusion, the concordance rate was highest for HBsAg, followed by HBeAg, anti-HBs, and anti-HBe. The concordance rate was greater between the two automated analyzers than those of each with IRMA for anti-HBs and HBeAg and the positive rates were highest with the Modular E170 assay for anti-HBe. This study shows substantial differences between the assay results by the three methods, which should be taken into account in determinations of serum HBV markers.


   Acknowledgments
 
The authors thank Abbott Diagnostics and Roche Diagnostics for donating the reagents for assays of HBV markers.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Lavanchy D. Hepatitis B virus epidemiology, disease burden, treatment, and current and emerging prevention and control measures. J Viral Hepat 2004;11:97–107.[Medline]
  2. Custer B, Sullivan SD, Hazlet TK, Iloeje U, Veenstra DL, Kowdley KV. Global epidemiology of Hepatitis B Virus. J Clin Gastroenterol 2004;38:158–168.
  3. Chen Y, Wu W, Li LJ, Lou B, Zhang J, Fan J. Comparison of the results for three automated immunoassay systems in determining serum HBV markers. Clin Chim Acta 2006;372:129–133.[Medline]
  4. Chen CH, Lee CM, Wang JH, Tung HD, Hung CH, Lu SN. Correlation of quantitative assay of hepatitis B surface antigen and HBV DNA levels in asymptomatic hepatitis B virus carriers. Eur J Gastroenterol Hepatol 2004;16:1213–1218.[Medline]
  5. Deguchi M, Yamashita N, Kagita M, Asari S, Iwatani Y, Tsuchida T, Iinuma K, Mushahwar IK. Quantitation of hepatitis B surface antigen by an automated chemiluminescent microparticle immunoassay. J Virol Methods 2004;115:217–222.[Medline]
  6. Ambrosch F, Courouce AM, Coursaget P, et al. Immunization against hepatitis B. Lancet 1988;331:875–876.
  7. Wang CW, Wang LC, Chang MH, Ni YH, Chen HL, Hsu HY, Chen DS. Long-term follow-up of hepatitis B surface antibody levels in subjects receiving universal hepatitis B vaccination in infancy in an area of hyperendemicity: correlation between radioimmunoassay and enzyme immunoassay. Clin Diagn Lab Immunol 2005;12:1442–1447.[Medline]
  8. Taylor P, Pickard G, Gammie A, Atkins M. Comparison of the ADVIA Centaur and Abbott AxSYM immunoassay systems for a routine diagnostic virology laboratory. J Clin Virol 2004;30(Suppl 1):11–15.[Medline]
  9. Oh SH, Choi SK, Park SY, Ki CS. Evaluation of serologic markers for HBV Infection using Roche Modular Analytics E170. J Lab Med Qual Assur 2005;27:167–172.
  10. Whang DH, Shin BM. Comparison of four-assay system for the quantification of hepatitis B surface antibody. Korean J Lab Med 2002;22:424–430.
  11. Heijtink RA, Schneeberger PM, Postma B, Crombach W. Anti-HBs levels after hepatitis B immunisation depend on test reagents: routinely determined 10 and 100 IU/L seroprotection levels unreliable. Vaccine 2002; 20:2899–2905.[Medline]
  12. Heijtink RA, Janssen HL, Hop WC, Osterhaus AD, Schalm SW. Interferon-alpha therapy for chronic hepatitis B: early response related to pre-treatment changes in viral replication. J Med Virol 2001;63:217–219.[Medline]
  13. Heijtink RA, Kruining J, Honkoop P, Kuhns MC, Hop WC, Osterhaus AD, Schalm SW. Serum HBeAg quantitation during antiviral therapy for chronic hepatitis B. J Med Virol 1997;53:282–287.[Medline]



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