Tottori J. Clin. Res. 8(1), 74-79, 2016

A case of HCV-positive conversion in antibody testing for hospital staff—From follow-up—
Michiyo Yamamoto*, Kiyoshi Okita, Ikuko Ohata, Hitoshi Takahashi
Department of Clinical Laboratory, NHO Tottori Medical Center*Correspondence: 876 Mitsu, Tottori 689-0203
Abstract
HCV antibody testing is a screening test for the hepatitis C virus (HCV). Numerous immunological measurement
methods are presently being used. However, the reactivity of testing reagents may vary depending on the differences inmeasurement methodology and equipment even when the reagents are made by the same manufacturer. In this paper, wereport a case of an individual who tested positive in HCV antibody testing for staff at Hospital A but later tested negativein a reexamination conducted at another institution. This case was referred to the distributor of the testing reagent for
closer scrutiny. We also performed a follow-up using a modified reagent with improved reaction specificity. By using
the serum sample of this case, we were able to respectively reproduce the same results as obtained at Hospital A and theother institution with reagents with the same lot number. The HCV core antigen levels were below the detectable limit.
The result of an HCV antibody profile test was negative. In a test using different HCV antigen particles, high levelsof luminance count compared to those of the HCV antibody–negative control serum were detected in all particles
including unsensitized ones. The patient also tested negative with the modified reagent with improved HCV antibody
specificity. These results indicate that before the HCV-positive conversion occurred and after the last negative result wasobtained, some sort of immunological stimulus might have induced the production of nonspecific substances in thepatient’s blood that would react to different antigen particles in the reagent. Moreover, these results also indicate that theuse of modified reagents with improved specificity might reduce the likelihood of nonspecific reactions. Tottori J. Clin.
Res. 8(1), 74-79, 2016
Key Words: Hepatitis C virus (HCV), HCV antibody testing, screening, HCV-RNA testing, antibody profiling, different
antigen particles	 
1. Introduction
Hepatitis C is a hepatic disease caused by HCV
infection. In Japan, there are estimated to be between 1.5
and 2 million individuals with persistent HCV infection(HCV carriers). It has recently become known that some
HCV carriers can develop liver cirrhosis and liver cancer.
The HCV is primarily transmitted via blood, and in thepast, many cases of infection were caused by bloodtransfusion and administration of blood preparations. In
1989, however, blood centers nationwide adopted a
testing method aimed at preventing HCV infection,
namely HCV c100-3 antibody testing (first-generation
antibody testing). Since then, next-generation antibody
testing methods with higher accuracy have been
introduced one after another, making HCV infection via

blood transfusion a rarity. Moreover, the introduction ofHCV-RNA testing in 1999 has further improved thesafety of blood transfusion and preparations.
HCV antibody testing is the method of choice forscreening HCV infection. However, as there are many
immunological measurement techniques, levels ofreactivity may vary depending on the differences inmeasurement methodology and equipment even whenreagents made by the same manufacturer are used.
Normally, individuals with HCV antibody–positive
serum are divided into “HCV carriers” and “alreadyinfected patients”. For clearer differentiation, the mostcommon modality presently employed is to perform
either HCV core antigen testing or nucleic acidamplification testing (NAT) on HCV antibody–positive