Background Systemic lupus erythematosus (SLE) patients are at an increased risk for infection. It is known that some SLE patients develop severe acute illnesses and require admission to the intensive care unit (ICU). Infection is one of the most common causes for admission to the ICU and SLE patients may have vague clinical signs and symptoms due to their impaired immune responses to infection.
Objectives In this retrospective study, we examined clinical presentations and outcomes of SLE patients admitted to the ICU for infection and compared them to SLE patients admitted for non-infectious causes and to non-SLE patients admitted with infection.
Methods SLE patients with infection, SLE patients with non-infecious causes and non-SLE patients with infection were identified from the Cooper University Hospital Project IMPACT database between 2002 and 2010. Project IMPACT is a nationally representative, voluntary, fee based database system used to measure and describe the care of intensive care patients in the USA. The following information was obtained from the database: demographic data (age, gender), acute physiology and chronic health evaluation II (APACHE II) scores, physiologic data (temperature, heart rate (HR), systolic blood pressure (SBP)), laboratory data (white blood cell (WBC) count, hematocrit, creatinine(Cr)), length of stay in the ICU, length of stay in the hospital and mortality. Mann Whitney U (median difference) Pearson Chi Square and Fisher Exact Tests were used for all univariate significance tests.
Results Twenty five SLE patients with infection, 45 SLE patients with non-infectious causes and 1466 non-SLE patients with infection were included in the study. SLE patients with infection had significantly longer ICU length of stay, higher APACHE II scores, higher maximum temperature, higher minimum and maximum HR and lower minimum and maximum SBP in comparison to the SLE with non-infectious causes group. There was no significant difference in minimum and maximum WBC count between the two groups. The distribution of WBC count was generally less than 15,000/µL in the SLE group with infection.
Mortality was 40.0% in the SLE with infection group, 11.1% in the SLE with non-infectious causes group and 31.8% in the non-SLE with infection group. There was increased risk of mortality in the SLE group with infection relative to the SLE with non-infectious causes group that was statistically significant (p <0.01). There was no difference in mortality unadjusted for age and gender (p=0.39, OR=1.43, 95% CI=0.64-3.21) and in mortality adjusted for age and gender (p=0.27, OR= 1.67, 95% CI=0.67-4.15) between the SLE with infection group and the non-SLE with infection group.
Conclusions SLE patients with infection in the ICU had a higher mortality and a higher APACHE II score compared to SLE patients with non-infectious causes in the ICU. Their physiologic signs including temperature, HR and SBP were more reflective of infection than their WBC count. Our data raises the possibility that WBC count is misleading in diagnosing infection in SLE patients admitted to the ICU.
Disclosure of Interest None Declared