HI welcome to healthcare magic... Usually if some one needs to test for alcohol use , the test used is blood alcohol levels which would show a higher levels in you and they might know that you had alcohol. LFT is liver function test -alcohol if taken for a longer timer or taken in very heavy amounts can damage liver and so when a liver function test is done , it may be deranged and is an indirect evidence for alcohol consumption . MCV - is mean carpuscular volume - usually alcoholics dont eat , so usually suffer from Vit B12 and folic acid deficiancy which shows up as Macrocytic anaemia ,i.e MCVwill be high 100 .again indirect evidence of long standing alcoholism. CDT stands for Carbohydrate deficient transferrin which will again be increased in alcoholics. So all the tests you said are for testing long term effects of alcohol use , they would be normal if u just started to use alcohol.But if you are using alcohol since long time than they may show up as positive.. Hope i answered your question.