Ordering Recommendation

Useful for confirming a diagnosis of systemic lupus erythematosus (SLE) or mixed connective tissue disease (MCTD) following a positive ANA result. Antibodies may be useful in the differential diagnosis of other systemic autoimmune rheumatic diseases such as systemic sclerosis, Sjögren syndrome, polymyositis, dermatomyositis, and overlap syndromes.

Mnemonic

SMITH_RNP

Methodology

Semi-Quantitative Multiplex Bead Assay

Performed

Sun-Sat

Reported

1-2 days

New York DOH Approval Status

This test is New York DOH approved.

Specimen Required

Patient Preparation
Collect

Serum Separator Tube (SST).

Specimen Preparation

Separate from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.2 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions

Plasma or other body fluids. Contaminated, hemolyzed, or severely lipemic specimens.

Remarks
Stability

After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles)

Reference Interval

Test Number
Components
Reference Interval
0050470 Smith/RNP (ENA) Antibody, IgG
29 AU/mL or less Negative
30-40 AU/mL Equivocal
41 AU/mL or greater Positive

0050085 Smith (ENA) Antibody, IgG
29 AU/mL or less Negative
30-40 AU/mL Equivocal
41 AU/mL or greater Positive

Interpretive Data

Refer to report.

Compliance Category

FDA

Note

Hotline History

N/A

CPT Codes

86235 x2

Components

Component Test Code* Component Chart Name LOINC
0050085 Smith (ENA) Antibody, IgG 18323-6
0050470 Smith/RNP (ENA) Ab, IgG 33983-8
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.

Aliases

  • Anti-Sm
  • Anti-Smith (ENA) Antibody
  • Sm antibody IgG
  • Sm/RNP
  • Sm/RNP Antibody
Smith and Smith/RNP (ENA) Antibodies, IgG