Despite improvements achieved in laboratory medicine over the years, discrepant results from different clinical laboratories are still a source of imminent risk to patients and the pharmaceutical industry. The problem is aggravated by a disconnect between the in vitro diagnostic community and clinicians or drug developers. This is the sequel to a previous report where data from proficiency testing, originally established as a tool for good laboratory practice, were used to highlight the size of the problem, and its possible impact on patients and pharmaceutical trials. Results from three laboratory tests commonly used as tools to monitor patients undergoing therapy with heparin or antithrombin agents, activated partial thromboplastin time, anti-factor Xa and thrombin time, were investigated. Unfortunately, data show that, owing to an absence of standardization approaches or a reasonable technique to harmonize results from different laboratories, results for the same sample, if analyzed by different laboratories or even by one laboratory employing different platforms or reagents, can be extremely different and misleading.