How likely would be a false positive test result of tyrosinuria in metabolic urine screening after 12 hours fasting? If indeed pos., what is the cause

Rare entity if true. This is a rare condition that can be treated with a low phenylalanine/tyrosine diet. Blurry vision could be related but unlikely. High cholesterol and triglycerides are probably unrelated. Tyrosinuria is a genetic disease most common in french canadians. Repeat test if marginally abnormal.