First, the Nationwide Inpatient Sample (NIS) underwent significant revisions between 1993 and 2012. The 1993 sample covered only 17 states and represented approximately 54% of the US population, whereas by 2012, the NIS captured patients from 44 states covering approximately 96% of the US population. The authors' use of US Census data to create the denominator for national rates of pulmonary embolism (PE) admissions during the study period may not be correct given the limited scope of earlier years of the NIS. Also, there was a complete redesign of the NIS sampling methods for the year 2012 that requires significant adjustments for trend analysis when comparing with previous years. The authors made no comment on adjustments for trend analyses accounting for changes in the NIS, including the major redesign for 2012. Also, it is assumed, but not stated, by the authors that proper complex survey procedures were used in the analysis of the data set.