Thanks for your question on HCM. Yes you are right. Long duration of time for transporting blood samples can alter the result. And hepatic encephalopathy is not only laboratory diagnosis. It is more of a clinical diagnosis. Yes, high ammonia level is helpful in diagnosis but clinical judgement is must. Recent studies suggest that ammonia level can help in predicting encephalopathy. Means high ammonia level suggest high chances of developing encephalopathy. So better to recheck it with other lab.