**3. Results**

#### *3.1. Patient Characteristics and In-Hospital Treatment*

Of 93,377,054 hospital admissions during the study period, 964 patients were admitted to hospital with GS as the principal diagnosis. The mean age of patients was 54 ± 21 years; 47% were female, 65% were Caucasian, and 9% had a co-diagnosis of ANCA-associated vasculitis. Of patients with GS, 19% needed invasive mechanical ventilation, 5% needed non-invasive ventilation support, and 52% required renal replacement therapy. Plasmapheresis was performed in 39% of patients. Table 1 shows clinical characteristics and in-hospital treatment of GS patients in this cohort.




**Table 1.** *Cont.*

#### *3.2. Inpatient Prevalence of GS*

Table 2 shows the annual distribution and inpatient prevalence of GS in hospitalized patients. The inpatient prevalence of GS ranged from 6.7 to 12.1 per 1,000,000 admissions between the years 2003 and 2014 in the United States with an overall inpatient prevalence of GS over 12 years of 10.3 cases per 1,000,000 admissions (Figure 1).


**Table 2.** The distribution and inpatient prevalence of Goodpasture's syndrome from 2003 to 2014.

**Figure 1.** Rate of hospital admission and in-hospital mortality rate for Goodpasture's syndrome stratified by year.

#### *3.3. Organ Failure and In-Hospital Mortality*

Seventy-six percent of patients had at least one end-organ failure. Renal failure was the most common end-organ failure (62%), followed by respiratory failure (29%), metabolic failure (17%), hematologic failure (13%), circulatory failure (6%), neurological failure (5%), and liver failure (1%) (Table 1). The number of end-organ failures was significantly associated with increased in-hospital mortality with an adjusted OR of 2.19 (95% CI 0.45–10.58) for one end-organ failure, 7.60 (95% CI 1.67–34.56) for two end-organ failures, and 19.86 (95% CI 4.10–96.19) for ≥3 end-organ failures.

Of 964 patients with GS, 74 (8%) died in the hospital. In the multivariable logistic regression, age older than 70 years (OR 3.62; 95% CI 1.52–8.61 compared to age ≤ 39 years), sepsis (OR 5.38; 95% CI 2.53–11.45), respiratory failure (OR 7.41; 95% CI 3.85–14.26), circulatory failure (OR 7.85; 95% CI 3.37–18.26), renal failure (OR 2.55; 95% CI 1.21–5.37), and liver failure (OR 32.32; 95% CI 3.51–297.19) were associated with increased in-hospital mortality. In contrast, more recent year of hospitalization (OR 0.23; 95% CI 0.10–0.55 for year 2011–2014 compared to year 2003–2006) and the use of therapeutic

plasmapheresis (OR 0.43; 95% CI 0.22–0.84) were associated with decreased in-hospital mortality (Table 3).


**Table 3.** Univariable and multivariable analysis assessing factors associated with in-hospital mortality in Goodpasture's syndrome patients.

#### *3.4. Length of Hospital Stay and Hospitalization cost*

The median length of hospital stay was 10 (IQR 5–18) days. The median hospitalization cost was \$75,831 (IQR 31,687–163,201) (Table 1).
