Are there any medications, specifically for OCD or other related conditions, which would mask the results of a blood test for Hepatitis C? A friend of mine was told he had to go off his meds for ten days in order to get an accurate reading.

I'm not sure about the masking the results as in false-negative or a false-positive, but acetaminophen (Tylenol) is definitely one of those drugs that can change the read of liver problems.

Many OCD medications have an effect on the liver as well...can potentially cause damage and also change the way that the liver breaks down other meds...

They may want to ensure that they are getting an accurate read on what the potential damage to the liver may be in addition to testing itself.

The CDC has this Hepatitis C FAQ article that says all of the tests look for either antibodies to viral antigen or RNA from the virus itself. Neither method is likely to be thrown off by the presence of additional chemicals: the active binding site of an antibody molecule is remarkably stereo-specific for its antigen, while RNA matching obviously involves specific base sequences. So I doubt that stopping the medication would matter in diagnosing Hepatitis C. Of course his doctor knows best.

But if hepatitis is already strongly suspected, the doctor would want to assess liver damage, which includes blood levels of certain enzymes. Here's a semi-technical article from American Academy of Family Physicians: Special Considerations in Interpreting Liver Function Tests.

Many medications are metabolized by enzymes in the liver. Some medications can cause the liver to make additional enzyme by inducing genes in the liver cells. Other drugs might be mildly toxic to the liver. Either way the result is elevated serum enzymes, in effect a red herring in the search for hepatitis-associated liver injury. Hence the temporary stoppage. That's my educated guess.

Good luck to your friend.

Thanks a lot. I figured meds would not mask the presence of Hep C, so the damage extent was probably the factor.