Laboratory Tests and Ancillaries
The
lab tests performed for the diagnosis of systemic lupus erythematosus 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.
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. Renal biopsy is
recommended in all patients with evidence of kidney involvement, particularly
those with persistent proteinuria (≥0.5 g/24 hr or UPCR ≥500 mg/g), glomerular
hematuria, and/or unexplained decrease in glomerular filtration rate (GFR).
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 Systemic Lupus
Erythematosus (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.