Long term outcome of patients with low level of cryoglobulin (<0.05g/L)

Objectives: To date, no studies have yet assessed the characteristics of non-HCV patients with low level of cryoglobulin (≤0.05 g/L). The aims of the current study were thus to: 1) determine the prevalence of cryoglobulin ≤0.05 g/L in patients with non-HCV cryoglobulin; and 2) compare clinical features and long term outcome, including organ complications and mortality rate, between non-HCV patients with cryoglobulin level ≤0.05 g/L and those exhibiting cryoglobulin level >0.05 g/L.

Methods: Among 6379 cryoglobulin testing, cryoglobulin was detected in 618 patients (9.69% of cases); of these 618 patients, 453 non-HCV patients were included in the study. The medical records of these patients were reviewed.

Results: Of the 453 non-HCV cryoglobulin-positive patients, 265 (58.6%) exhibited cryoglobulin level ≤0.05 g/L. We showed that patients with cryoglobulin level ≤0.05 g/L had: 1) less commonly: palpable purpura (p<0.001), digital ulcers (p=0.006), peripheral neurologic involvement (p=0.03) and renal impairment (p=0.03); and 2) lower median values of ESR (p<0.001) and C-reactive protein (p=0.001). The patients with cryoglobulin level ≤0.05 g/L less often experienced infections (p=0.04) and hematological malignancies (p=0.01); both groups did not differ regarding prevalence of connective tissue diseases and solid tumors. Mortality rate was as high as 13.6% in patients with cryoglobulin level ≤0.05 g/L; death was mainly due to: solid tumors (16.6%), cardiovascular complications (13.8%), hematological malignancies (11.1%), infections (8.3%), pulmonary/renal complications of cryoglobulin (8.3%) and connective tissue diseases (8.3%).

Conclusion: Our study shows a high prevalence of cryoglobulin level ≤0.05 g/L in clinical practice. Our findings further underscore that non-HCV cryoglobulin level ≤0.05 g/L may be responsible for severe renal and neurological complications, leading to high morbidity and mortality in these patients. Thus, our data suggest that both appropriate therapy and close follow-up may be required to improve such patients' outcome.