Please refer to the following suggestions...
First, you are mentioning "asthma" in your medical history. May I know if you are taking any drugs on daily or occasional use? - This is to clarify whether the isolated elevation of gamma gt
could be related to drugs used for relieving asthma symptoms: NSAIDS, aspirin
Another factor could be the viral infection which could have touched the gall bladder
. - Please bare in mind that viral infections before showing their "notable" symptoms, have their prodromal stage.
Hope it answered to your inquiry!
p.s. if you have more questions, please write back to me!