[Significance of hepatitis B core antibody as the only marker of hepatitis B infection]. / Significado de la reactividad aislada anti-HBc como único marcador de infección de la hepatitis B.

INTRODUCTION: Little is known about the clinical significance of the "anti-HBc alone" serological profile (absence of HBsAg and anti-HBs) in HBV infections. The objective of the present study was to estimate the prevalence of the anti-HBc alone immunological profile and the clinical-epidemiological characteristics of patients with this profile. METHODS: Prospective, cross-sectional, descriptive study performed in 2002 and including patients with anti-HBc alone (HBsAg-negative, anti-HBs-negative and anti-HBc-positive). All the cases identified underwent the following microbiological tests: IgM anti-HBc, HBeAg, anti-HBe, anti-HDV, anti-HCV, anti-HIV, as well as HBV-DNA testing by qualitative nested-PCR. Furthermore, studies of serum biochemical parameters, blood counts and coagulation, as well as a clinical-epidemiological interview were performed in all patients. RESULTS: Among 3900 patients studied, 195 (5%) presented the anti-HBc alone profile (48% were > 65 years old). Residual anti-HBs (< 10 mUI/mL) was found in 44% of cases and 33% were anti-HBe positive. HCV or HIV coinfection were seen in 38% and 8%, respectively. HBV-DNA was detected in 4.2% (5/120) of cases. Epidemiologically, detection of anti-HBc alone was casual in 60% of patients, whereas the remaining cases had a history of chronic liver disease (82% of these were anti-HCV positive). In a high percentage (63%) the transmission mechanism of HBV infection was unknown (11% intravenous drug abuser, 10% surgery, 6% transfusions). CONCLUSION: The anti-HBc alone pattern is a frequent finding, particularly in patients > 65 years old and in HCV or HIV coinfected patients. Although HBV-DNA was detected in a small percentage of cases, this test could be indicated in certain clinical situations (liver disease, coinfection, donors). Furthermore, this profile seems to be related with HCV infection; hence, we consider anti-HCV detection necessary in all patients with anti-HBc alone.