What laboratory finding is indicative of primary sclerosing cholangitis (PSC)?

• A. Negative p-ANCA
• B. Positive anti-mitochondrial antibodies
• C. Positive p-ANCA
• D. Elevated bilirubin levels

Answer: (C)

Primary sclerosing cholangitis (PSC) is a chronic autoimmune disease characterized by progressive inflammation and scarring of the bile ducts. A key laboratory finding commonly associated with PSC is the presence of positive perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA), particularly in conjunction with the presence of myeloperoxidase (MPO) antibodies.

The positivity of p-ANCA serves as a useful serological marker in diagnosing PSC, especially since the disease often presents in conjunction with inflammatory bowel disease, such as ulcerative colitis. The presence of these antibodies helps to reinforce the autoimmune nature of PSC and provides insight into the underlying pathophysiology of the disease.

Elevated bilirubin levels may also be observed in PSC due to bile duct obstruction and subsequent liver dysfunction; however, they are not specific to PSC and can occur in many other liver diseases. Therefore, the presence of positive p-ANCA serves as a more definitive indicator for PSC in the context of laboratory findings.