The General and Socio-demographic characteristics
A total of 521 patients were enrolled, including 400 patients hospitalized once and 121 patients hospitalized repeatedly, and 23.2% of the patients were readmitted within one year. Hospital stays were longer in patients with readmission during the first hospitalization than in patients without readmission (11.0±8.4 vs. 9.0±6.0 days, P=0.007). Age at SLE onset and first hospitalization were higher in the readmission group (35.8±17.0 vs. 31.6±13.3 years, P=0.007; 40.3±16.4 vs. 35.5±13.6 years, P=0.015, respectively). In addition, gender, disease duration, payment method, hospitalization cost, local GDP per capita, and geographical distance from hospital were compared between the two groups, and the differences were not statistically significant (Table 1).
The incidence of kidney damage and hypertension in the SLE patients with readmission was significantly higher than that in the SLE patients without readmission (Table 2) (63.9% vs. 50.4%, P=0.01; 12.4% vs. 4.0%, P=0.001, respectively). There were no statistically significant differences in other clinical symptoms, including fever, alopecia, arthritis, edema, convulsion, erythra, dental ulcers, or other complications between the two groups (Table 2).
Laboratory Examination and Renal Pathology
Patients with SLE who were readmitted had lower hemoglobin and albumin levels than patients without readmission (P=0.005 and P<0.001, respectively) during initial hospitalization, and higher urea nitrogen, total cholesterol, cystatin C, serum creatinine, blood uric acid, and triglycerides levels than patients without readmission (all P <0.005) (Table 3). There were no statistically significant differences in white blood cell counts, platelet counts, aspartate aminotransferase, alanine aminotransferase, total bilirubin, complement, antinuclear antibody series, or urine protein levels between patients (Table 3). More patients underwent renal biopsy in SLE patients who were readmitted than patients without readmission (33.1% vs. 20.8%, P=0.006). Type IV lupus nephritis was common in both groups, but there was no statistically significant difference in renal pathological types between the groups.
Analysis of risk factors associated with readmission and reasons for readmission in SLE patients within 1 year
Univariate logistic regression analysis was applied to define the risk factors for readmission in patients with SLE within 1 year in general and in relation to sociodemographic characteristics, clinical characteristics, laboratory examination results, and renal pathology. Finally, the onset age, duration of the first hospitalization, the hemoglobin, albumin, urea nitrogen, total cholesterol, cystatin C, serum creatinine, uric acid, blood triglycerides levels, and kidney damage were confirmed to be statistically significant. Multicollinearity analysis was performed among the screened risk factors, and the results showed VIF < 10, suggesting that there was no multicollinearity among these risk factors. However, cystatin C, urea nitrogen, and serum creatinine are highly correlated, and cystatin C is reported to be more sensitive. The screened risk factors excluding serum creatinine and urea nitrogen were enrolled, and multivariate logistic regression analysis was applied. The results showed that the age of onset (OR 1.022, 95%CI 1.007-1.036), albumin (OR 0.965, 95%CI 0.942-0.989), and cystatin C (OR 1.404, 95%CI 1.180 -1.670), were closely related to readmission (Table 4).
The most common causes of readmission were infection (52 cases, 27.08%), lupus activity or recurrence (45 cases, 23.4%), review and consolidation treatment (16 cases, 8.3%), and readmission due to cardiovascular and cerebrovascular diseases (12 cases, 6.25%) (Table 5).The most common infection factors in readmitted SLE patients were respiratory tract infection (29, 60%), followed by herpes zoster (8,14%), skin and soft tissue infection (7,12%), urinary tract infection (4,7%), and other factors such as nervous system infection, acute peritonitis, and pelvic inflammatory mass (Table 5).