Systemic Lupus Erythematosus Diagnostics

Laboratory Tests and Ancillaries

The lab tests performed for the diagnosis of SLE include a complete blood count (CBC), urinalysis, liver and renal function tests, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), antinuclear antibodies (ANAs), anti-double stranded deoxyribonucleic acid (anti-dsDNA), complement 3 and 4 (C4 and C4), and antiphospholipid antibodies.  

ANAs are present in approximately 95% of patients with systemic lupus erythematosus. A negative test indicates a low clinical probability of systemic lupus erythematosus; a positive test alone has a poor diagnostic value without the clinical features of autoimmune rheumatic disease.  

The entry criterion in the diagnosis of systemic lupus erythematosus is an ANA titer of ≥1:80 on HEp-2 cells or an equivalent positive test is measured at least once. It is recommended to test by indirect immunofluorescence on HEp-2 cells or a solid-phase ANA screening immunoassay with at least equivalent performance. If the patient is ANA negative, an alternative entry criterion could be low complement levels and/or the presence of antiphospholipid antibodies.  

Specific Manifestations of Systemic Lupus Erythematosus  

Lupus Nephritis  

Patients suspected of having lupus nephritis should immediately undergo a renal biopsy to confirm the diagnosis, evaluate severity, and determine prognosis and therapy.  

The indications for renal biopsy in systemic lupus erythematosus patients include an unexplained increase in serum creatinine in the absence of alternative causes (eg sepsis, hypovolemia, medications) and confirmed proteinuria of ≥1 g/24 hr or reproducible proteinuria of ≥0.5 g/24 hr plus glomerular hematuria and/or cellular casts.  

Please see Lupus Nephritis disease management chart for further information.  

Neuropsychiatric SLE (NPSLE)  

Diagnostic work-up may include lumbar puncture, nerve conduction studies (NCS), neuropsychological assessment of cognitive function, cerebrospinal fluid analysis, electroencephalography (EEG), and neuroimaging such as T1/T2 MRI, diffusion-weighted imaging, or gadolinium-enhanced T1 sequences.