I wouldn't hit the panic alarm just yet. If there is something critical, they wouldn't put it off until Friday. You may have shown some abnormal levels hence the follow up on Friday. It could be a million things so try and relax a little. If you are that worried, call into the office and tell them the nature of your concern and waiting until Friday just won't cut it. They always have a little pad time built in and certainly could see you for 15 minutes to go over your labs. Sometimes you just have to be stern in your approach though.

Good Luck

Doc M