What is the blood test that could be a marker to detect early cirrhosis?

More than one/many.: Cirrhosis is a broad condition that covers so many causes that there are many blood tests that indicate it and the cause. In general cirrhosis, low red cell count, low albumin, and high prothrombin time, indicate the liver's inability to do its job due to cirrhosis. These can happen before cirrhosis and can mean worse prognosis. Hepatitis abs, anti-mitochondrial ab, etc. Point to the causes.

A few but none good: biopsy or fibroscan are really a lot more reliable. FIB-4, APRI, Fibrosure are all used in trying to detect advanced fibrosis/early cirrhosis - but they're poorly reliable.