Clarification On Blood Testing

HV,
I would like to know what you recommend someone does in order to determine if they have a certain disease or condition? I was reading some of you past posts and you mentionend that allot of Doctor recommended tests were not accurate, is this true? Do you recommend blood test or one go by symptoms? I understand that blood test can result in false positives, but am a bit confused as you mention that one should not self diagnose. So, if I'm correct we should goto our regular Doctor depending on our problem, and then decide independently whether we want to take the allopathic or alternative treatment, right? There is allot of conflicting information here on this site. I was reading one thread on the Barefoot forum, someone had asked a question regarding PH balancing and that there friend was eating junk and there ph stript that was tested showed an alkaline side (name of thread is "Don't Understand"). Barefoot was saying that by doing a fast all the acids in the body will start to flow outward. He is another proponent of the acid causing disease as well. He feels that we should eat natural fruits only..I just find the information here and there so conflicting, please make my understand..Thanks...