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. Author manuscript; available in PMC: 2019 May 1.
Published in final edited form as: Crit Care Med. 2018 May;46(5):764–773. doi: 10.1097/CCM.0000000000003015

Table 2.

Demographic and Clinical Characteristics of ARDS Cases by In-Hospital Mortality Status; NIS 2002-2011 (N=117,204)

Variable Mortality status Odds ratio (CI) p-value
Alive
N = 68,848		 Died in hospital
N = 48,356
Demographic
Age in years, mean (SD) 58.42 (18.17) 66.29 (17.48) 1.03 (1.02-1.03) < 0.001
Age group, years, %
 18-29 9.01 4.68 ref ref
 30-39 7.89 4.44 1.08 (0.99-1.18) 0.03
 40-49 13.10 8.21 1.21 (1.11-1.31) < 0.001
 50-59 18.10 13.54 1.44 (1.34-1.55) < 0.001
 60-69 19.84 18.03 1.75 (1.63-1.88) < 0.001
 70-79 20.20 25.51 2.43 (2.26-2.61) < 0.001
 ≥80 11.87 26.50 4.15 (3.86-4.47) < 0.001
Female, % 41.40 44.85 1.15 (1.12-1.19) < 0.001
Race, %
 White 58.48 59.36 ref ref
 Black 9.87 9.56 0.95 (0.90-1.01) 0.02
 Hispanic 7.54 7.18 0.94 (0.88-1.00) 0.01
 Asian or Pacific Islander 1.51 1.90 1.25 (1.11-1.40) < 0.001
 Native American 0.55 0.45 0.81 (0.65-1.01) < 0.001
 Other 2.77 2.75 0.98 (0.89-1.08) 0.57
Expected Primary Payer, %
 Medicare 44.48 59.79 ref ref
 Medicaid 12.93 8.89 0.51 (0.49-0.54) < 0.001
 Private including HMO 31.36 21.93 0.52 (0.50-0.54) < 0.001
 Self-pay 5.31 5.45 0.76 (0.81-0.82) < 0.001
 No charge 0.73 0.47 0.48 (0.39-0.59) < 0.001
 Other 4.91 3.27 0.50 (0.46-0.54) < 0.001
Comorbid Conditionsa
Elixhauser Comorbidity Score, mean (SD) 7.63 (7.20) 8.98 (7.44) 1.03 (1.02-1.03) < 0.001
Severity Measures, %
APR-DRG risk of mortalityb
 Minor likelihood of dying 2.49 0.25 ref ref
 Moderate likelihood of dying 10.12 1.97 1.95 (1.50-2.52) < 0.001
 Major likelihood of dying 33.96 18.32 5.41 (4.23-6.91) < 0.001
 Extreme likelihood of dying 52.57 78.46 14.97 (11.73-19.10) < 0.001
APR-DRG severity of illness subclassb
 Minor loss of function 0.03 0.01 ref ref
 Moderate loss of function 0.82 0.49 1.93 (0.53-6.98) 0.19
 Major loss of function 9.86 9.35 3.06 (0.86-10.92) 0.02
 Extreme loss of function 88.43 89.43 3.26 (0.91-11.61) 0.02
Discharge Quarter
 January –March 25.11 26.46 ref ref
 April-June 25.91 25.14 0.92 (0.88-0.96) < 0.001
 July-September 25.60 25.02 0.93 (0.89-0.97) < 0.001
 October-December 23.33 23.29 0.95 (0.91-0.99) < 0.001
Admission-Weekday v. Weekend
 Monday-Friday 78.00 77.95 ref ref
 Saturday or Sunday 22.00 22.05 1.00 (0.97-1.01) 0.84
Admission Typec
 Emergency 46.51 52.60 ref ref
 Urgent 14.76 15.24 0.91 (0.87-0.95) < 0.001
 Elective 21.82 16.23 0.66 (0.63-0.69) < 0.001
 Trauma center (beginning in 2003) 6.12 3.79 0.55 (0.51-0.59) < 0.001
 Other 0.02 0.01 0.37 (0.10-1.37) 0.05
Length of Stay, Median (IQR) 23 (16-35) 10 (4-19) 0.94 (0.94-0.95) < 0.001
OR Procedure 77.16 63.61 0.52 (0.50-0.54) < 0.001

ARDS = Acute Respiratory Distress Syndrome; APR-DRG = All patient refined diagnosis related grouping; CI = 99% confidence interval; HMO = Health Maintenance Organization; NIS=Nationwide Inpatient Sample; OR = operating room; SD = standard deviation

a

This represents a weighted Elixhauser Score based on comorbidities on discharge record. Comorbidities within the Healthcare Cost and Utilization Project (HCUP) are determined using the Agency for Healthcare Research and Quality (AHQR) comorbidity software which seeks to identify comorbid medical conditions present prior to admission (https://www.hcup-us.ahrq.gov/tools_software.jsp).

b

The All Patient Refined Diagnosis Related Grouping (APR-DRG) risk of mortality and severity of illness subclass are assigned using a software developed and maintained by 3M Health Information Systems (www.hcup-us.ahrq.gov). Category of ‘Minor loss of function’ includes cases with no comorbidity or complication.

c

11.33% of observations missing data on this variable.