Systemic lupus erythematosus laboratory tests

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: {{MIR}

Overview

Laboratory findings consistent with the diagnosis of systemic lupus erythematosus include anemia, leukopenia or lymphopenia, elevated levels of ANA, anti-dsDNA, anti-SM and antiphospholipid, and decrease of complement levels.

Laboratory tests

Laboratory findings consistent with the diagnosis of systemic lupus erythematosus include anemia, leukopenia or lymphopenia, elevated levels of ANA, anti-dsDNA, anti-SM and antiphospholipid, and decrease of complement levels.

	Lab exam	result	clinical correlation
Hematology	Complete blood count	Leukopenia Lymphopenia Mild anemia Thrombocytopenia
	Serum creatinine	Elevated	Suggestive of renal dysfunction
	Amylase-Lipase	Elevated	Acute pancreatitis
Urine	Urinalysis Urine sediment	Hematuria Pyuria Proteinuria Cellular casts
Serology	ANA	Elevated	Positive in virtually all patients with SLE at some time in the course of their disease
	Antiphospholipid antibodies	Lupus anticoagulant [LA] IgG and IgM anticardiolipin [aCL] antibodies IgG and IgM anti-beta2-glycoprotein [GP]	aPLs are a heterogenous group of autoantibodies which are directed against phospholipid-binding proteins
	complement levels	C3: vary between varying between normal to slightly reduced C4: reduced CH50: reduced	Impaired clearance of immune complexes Impaired handling of apoptotic cells Aberrant tolerance induction or changes in cytokine regulation During disease flares, the complement system is activated giving rise to partial deficiency or dysfunction due to consumption Takes part in the inflammatory reaction in the diseases which lead to the tissue and organ damage
	Erythrocyte sedimentation rate (ESR)	Elevated
	C-reactive protein (CRP)	Elevated
	Urine protein-to-creatinine ratio	Elevated
	Anti-dsDNA	Elevated	Highly specific for SLE In 70% of patients
	anti-Sm antibodies	Elevated	Highly specific for SLE In 30% of patients Lack sensitivity
	Anti-Ro/SSA antibodies	Elevated	In 30% of patients More commonly associated with Sjögren’s syndrome
	anti-La/SSB antibodies	Elevated	In 20% of patients More commonly associated with Sjögren’s syndrome
	Anti-U1 RNP antibodies	Elevated	In approximately 25 percent of patients with SLE Not specific, always present in patients with mixed connective tissue disease (MCTD)
	Antiribosomal P protein antibodies	Elevated	High specificity for SLE & low sensitivity for SLE Lack specificity for involvement of a particular organ system or disease manifestation
	Direct Coombs' test	Positive	Clinically important in the absence of other causes of hemolytic anemia

If the initial ANA test is negative, but the clinical suspicion of SLE is high, then additional antibody testing may still be appropriate. This is partly related to the differences in the sensitivity and specificity among the methods used to detect ANA.

Laboratory exams to distinguish SLE from other diseases

Test	Interpretation
anti-cyclic citrullinated peptide (CCP) antibodies	In patients with predominant arthralgias or arthritis may help exclude a diagnosis of rheumatoid arthritis (RA) Higher specificity for RA and may be more useful for distinguishing the arthritis associated with RA
Rheumatoid factor (RF)	Less diagnostic since only 20 to 30 percent of people with SLE have a positive RF
Serological studies for infection	Serologic testing for human parvovirus B19 In patients with a brief history (for example, less than six weeks) of predominant arthralgias or arthritis
	Serologic testing for hepatitis B virus (HBV) and hepatitis C virus (HCV) In patients with multi-systemic clinical findings
	Serologic studies for Borrelia Especially in areas endemic for Lyme disease
	Testing for Epstein-Barr virus (EBV)
Creatine kinase (CK)	Can reflect myositis (relatively uncommon in patients with SLE) Myositis may also suggest an alternative diagnosis such as: MCTD Polymyositis (PM) Dermatomyositis (DM)