RT Journal
A1 Walcott BP, Nahed BV, Coumans J
T1 HElicopter vs ground transportation for patients with trauma
JF JAMA
JO JAMA
YR 2012
FD August 8
VO 308
IS 6
SP 563
OP 565
DO 10.1001/jama.2012.7776
UL http://dx.doi.org/10.1001/jama.2012.7776
AB 
To the Editor: The authors of the study on helicopter vs ground EMS1 recognized the potential influence of missing data in the NTDB and attempted to overcome this limitation by using multiple imputation. While this was used for variables missing up to 20% of data, no accounting was made for the large percentage of patients whose discharge disposition was unknown (734 386 of 1 816 982; 40%). These patients were excluded from analysis, but one cannot assume that their outcome mirrored that of the rest of the study patients.