Such occult (meaning hidden or concealed) infection is not supposed to occur--the conventional wisdom is that the virus leaves markers in serum or plasma, including specific antibodies and viral RNA, which have been the serologic cornerstones for diagnosing and monitoring HCV-infected patients. Although occult HCV infection generally appears to be mild, some patients have shown evidence of serious chronic liver injury. In addition, occult infection raises the possibility of disease spread via blood donations, hemodialysis and other procedures. Fortunately, the study also suggests a minimally invasive approach to detect occult infection.
The study, reported by a group headed by Vicente Carreo, MD, in Madrid, Spain, involved 100 patients with abnormally high levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) or gamma glutamyl transpeptidase (GGTP) for at least 12 months in whom all causes of liver disease, including HCV infection, had ostensibly been excluded. All three liver enzymes were elevated in eight patients, two of the enzymes in 48 and one enzyme in 44. For comparison, 30 patients with liver damage known to be of non-viral origin were also studied.
The investigators relied on two assays to demonstrate the presence or absence of HCV infection. First, using reverse transcription-polymerase chain reaction (RT-PCR) with primers from one region of the HCV genome, they detected the virus's RNA in liver biopsies from 57 (57%) of the patients with abnormal liver enzymes of unknown etiology, compared to none of the biopsies from control patients. When primers from another region of the genome were used in the RT-PCR assay, HCV RNA was found in liver
Contact: Diana Olson
Infectious Diseases Society of America