Our initial database contained 471,112 adult intensive care admissions to 169 Pennsylvania hospitals from fiscal years 2005 to 2006. After exclusions, 138,720 patients were included in the final analysis: 95,995 (69.2%) were privately insured, 36,911 (26.6%) were insured by Medicaid, and 5,814 (4.2%) were uninsured (). Severity of illness, measured as the MediQual Atlas probability of death, was available for 74,353 (77.5%) privately insured patients, 25,533 (69.2%) Medicaid patients, and 3,829 (73.9%) uninsured patients.
Exclusions. FFS = fee for service; HMO = health management organization.
Patient demographic and clinical characteristics by insurance status are shown in . Uninsured patients were younger, with a mean age of 42 versus 50 years, were more likely to be men (71.3 vs. 59.7%), with a higher percentage of minorities (black 15.8 vs. 7.9%). The uninsured were more likely to be admitted to the hospital through the emergency department, with a higher percentage of trauma and nonsurgical admissions. Uninsured patients in our cohort also had fewer comorbidities and tended to have a lower MediQual probability of death. For those with Medicaid, the mean age, race, and median income fell between that of the uninsured and private insurance groups. Women made up a higher percentage of Medicaid patients, and Medicaid patients were more likely to have a higher MediQual death probability. For our primary outcome, uninsured patients had an absolute 30-day mortality of 5.7%, compared with 4.6% for those with private insurance and 6.4% for Medicaid.
DEMOGRAPHIC AND CLINICAL CHARACTERISTICS
We found substantial variation in the percent of uninsured patients cared for in the 167 hospitals included in our study (), ranging from 0 to nearly 20%, with uninsured patients accounting for less than 10% of the critically ill in the majority of Pennsylvania hospitals. In contrast, the proportion of Medicaid patients accounted for 0 to 80% of critically ill patients in individual hospitals (). With significant variation between the 167 hospitals included in our studies, Medicaid patients were found to constitute 10 to 50% of the critically ill in the majority of PA hospitals. When compared with patients with private insurance, uninsured patients were more likely to be admitted to small community hospitals, whereas Medicaid patients were more likely to be admitted to larger academic hospitals.
Histogram of the proportion of critically ill (A) uninsured and (B) Medicaid patients at 167 Pennsylvania hospitals 2004 to 2006.
Patients without insurance had an unadjusted 30-day mortality odds ratio (OR) of 1.26 (95% confidence interval [CI], 1.12–1.41; P < 0.001) when compared with those with private insurance (). The increased odds of death persisted after adjustment for patient variables (OR, 1.25; 95% CI, 1.04–1.51; P = 0.020). Furthermore, the increased odds of 30-day mortality persisted in our fixed-effects model that controlled for hospital site, with uninsured patients having a 25% higher odds of death within 30 days compared with privately insured patients (OR, 1.25; 95% CI, 1.04–1.50; P = 0.016). In unadjusted analysis, patients with Medicaid also had increased odds of 30-day mortality compared with those with private insurance, (OR, 1.42; 95% CI, 1.35–1.50; P < 0.001), but adjustment for patient characteristics eliminated this effect (OR, 1.06; 95% CI, 0.98–1.15; P = 0.164). Further adjustment for hospital center fixed effects again showed no difference in 30-day mortality for Medicaid patients when compared with the privately insured. Given the absence of center effects we used a marginal model to estimate the standardized absolute risk difference for 30-day mortality. We found an absolute risk difference of 0.01 (P = 0.011) when comparing patients alternatively as if they were all privately insured versus all uninsured, meaning for every 1,000 patients treated there would be 10 more deaths if everyone in our sample was uninsured.
ADJUSTED 30-DAY MORTALITY AND PROCEDURAL USE BY INSURANCE STATUS
In our analysis of five critical care procedures used as a proxy for ICU service use, the uninsured were significantly less likely to receive CVC, tracheostomy, and acute hemodialysis in our unadjusted analyses (). This effect, although attenuated, persisted after adjustment for patient characteristics and did not change when we additionally adjusted for hospital-level effects in our fixed-effects model: uninsured patients had decreased odds of CVC placement (OR, 0.84; 95% CI, 0.72–0.97; P = 0.018), acute hemodialysis (OR, 0.59; 95% CI, 0.39–0.58; P = 0.016), and tracheostomy (OR, 0.43; 95% CI, 0.29–0.64; P < 0.001). Although uninsured critically ill patients were also less likely to receive bronchoscopy or PAC in all models, results for these procedures did not reach statistical significance.
Medicaid patients were more likely to receive CVC, tracheostomy, and acute hemodialysis than the privately insured patients in unadjusted analyses. Although the effect size seen was attenuated by adjustment for patient characteristics and hospital-level fixed effects, Medicaid patients had increased odds of CVC (OR, 1.21; 95% CI, 1.14–1.28; P < 0.001), acute hemodialysis (OR, 1.21; 95% CI, 1.06–1.39; P = 0.006), and tracheostomy (OR, 1.16; 95% CI, 1.03–1.31; P < 0.019) in our final adjusted model. No difference was seen in our adjusted models for bronchoscopy or PAC for Medicaid patients when compared with those with private insurance.