Emergency physician tends to assume that the sample analysed by the lab and the results authenticated and released reflects what is happening in the patient. It is important to note that the clinical decision making process based on correlation with lab reports will be flawed and may have disastrous consequences if a system exists where the pre-analytical variables of Lab testing, especially coagulation tests are not considered and monitored. This review essentially highlights most important pre-analytical variables with the underlying mechanisms that if ignored can lead to correct analysis but wrong results if correlated to patients condition.