primary disease, or a combination of both In addition to usual laboratory testing, urinalysis, procalcitonin, and quantitative CRP provide a rapid and general overview of the patient’s well-being CH50 (or C4), C3, ANA, and anti-ds DNA, and extractable nuclear antigen (ENA) and possibly antiphospholipid antibody titers should be obtained in order to assess the degree to which the patient’s SLE is active An elevated procalcitonin and/or CRP without other evidence of active SLE is highly suggestive of bacterial infection Blood cultures are mandatory if no source of fever is apparent after a complete physical examination, and clinicians should have a low threshold for obtaining a chest x-ray, and for culturing CSF and other fluids when indicated In most cases, children with SLE who develop fever without a readily apparent source should be given antibiotics pending culture results; abnormal splenic function places them at increased risk of rapid development of bacteremia and overwhelming sepsis from encapsulated organisms