Rheumatoid factor and immunoglobulin M mark hepatitis C-associated mixed cryoglobulinaemia: an 8-year prospective study

The prevalence and factors of hepatitis C virus (HCV) -associated mixed cryoglobulinaemia in Asia remain elusive, and we aimed to investigate these topics. An 8-year prospective cohort study was conducted in 678 consecutive Taiwanese individuals with chronic HCV infection (438 completed an anti-HCV therapy course). Of 678 individuals, 437 (64.5%) had mixed cryoglobulinaemia and 20 (2.9%) had mixed cryoglobulinaemic syndrome. At baseline, IgM (cut-off >122 mg/dL), triglycerides and IgG levels, and HCV genotype 3 were independently associated with mixed cryoglobulinaemia. Rheumatoid factor (RF) levels were associated with mixed cryoglobulinaemic syndrome (cut-off >12.2 IU/mL). At 24 weeks post-therapy, the 362 individuals with a sustained virological response (SVR) had higher cured (106/362 (29.3%) versus 10/76 (13.2%), p = 0.003) and lower persistent (100/362 (27.6%) versus 33/76 (43.4%), p = 0.003) mixed cryoglobulinaemia rates than non-SVR patients. Among SVR patients, compared with baseline levels, RF, IgG and IgM levels decreased, except in individuals with new mixed cryoglobulinaemia. Pre-therapy IgM levels were associated with 24-week post-therapy new (95% CI of OR 1.002–1.023) and persistent (95% CI of OR 1.004–1.015) mixed cryoglobulinaemia in SVR patients. After up to 8 years, 24-week post-therapy IgM levels were associated with mixed cryoglobulinaemia in SVR patients (9/51; 17.64%; 95% CI of HR 1.004–1.011). Among 17 SVR patients with pre-therapy mixed cryoglobulinaemic syndrome, 5 (29.4%) had long-term mixed cryoglobulinaemia and 4 (23.5%) had mixed cryoglobulinaemic syndrome. Over 60% of chronic HCV-infected individuals had mixed cryoglobulinaemia, and 17.64% of SVR patients had mixed cryoglobulinaemia 8 years post-therapy. Pre-therapy RF and IgM levels marked HCV-associated mixed cryoglobulinaemic syndrome and mixed cryoglobulinaemia, respectively.