Human Sm Ab ELISA kit can be used for analysing in-vitro quantitative levels of IgG auto-antibodies to Smith antibodies (Sm Ab, anti-Sm IgG, anti-Sm antibody) using human serum and plasma. This assay has a minimum analytical sensitivity limit of 1.0 U/ml.


Smith antibodies (anti-Sm, anti-Sm antibody, Sm Ab) are made up of small nuclear ribonucleoprotein, consisting of a number of autoantigens ranging between 11-26 kD that are designated B, B1, D, E, F and G. Sm are essentially 1 of 4 autoantigens that are referred to as extractable nuclear antigens (ENAs), the other ENAs are SS-A/Ro, SS-B/La and RNP.

Antibodies to ENAs are present in patients with connective tissue diseases (including SLE), scleroderma, MCTD, Sjogren’s syndrome and polymyositis/dermatomyositis. The concentrations of Sm antibodies remain relatively constant in patients with SLE and they are also usually present in patients that possess RNP antibodies. Sm antibodies are highly specific (over 99%) for systemic lupus erythematosus (SLE) and therefore regarded as an important diagnostic marker for SLE.


All reagents supplied need to be stored at 2 °C – 8 °C, unopened reagents will retain reactivity until expiration date. Do not use reagents beyond this date.

  • Divisible Microplate: Consisting of 12 modules of 8 wells, highly purified Smith antibody bound to microwells.
  • Calibrators (A-F): Concentration 0-200 U/ml, made up from Sm antibodies.
  • Controls Positive and Control Negative: Containing human Sm antibody.
  • Sample Buffer (5x).
  • Enzyme Conjugate: Contains anti-human IgG antibodies, HRP labelled.
  • TMB Substrate.
  • Stop Solution: Contains acid.
  • Wash Buffer (50x Concentrated).
  • Instruction Manual.
  • Certificate of Analysis.


The minimum detection sensitivity level of human IgG against Smith antibodies (Sm antibody, Sm Ab, anti-Sm IgG) using current Sm antibody ELISA kit was 1.0 U/ml. The dynamic range for this assay is 12.5 – 200.0 U/ml.


– Smith Antibody (Anti-Sm): ELISA
– Measuring Range: 0 – 200 U/ml
– Linearity: 97 – 100%
– Limit Of Detection (LOD): 1 U/ml.
– Results Interpretation: Negative: < 15 U/ml, Borderline 15-25 U/ml, Positive: ≥ 25 U/ml.
– Expected Values: Cut-off 25 U/ml.
– Intra Assay: 2.0 – 4.1%
– Inter Assay: 1.3 – 5.3%
– Interference: None.
– Clinical Diagnosis: Sensitivity (51.4%), Specificity (95.8%), Overall agreement (79.5%).


  1. Association of cerebrospinal fluid anti-Sm antibodies with acute confusional state in systemic lupus erythematosus. Arthritis Res Ther. (2014) 16 (5): 450. Hirohata S., et al.
  2. Sm peptides in differentiation of autoimmune diseases. Adv Clin Chem. (2011) 54: 109-28. Review. Mahler M.
  3. Clinical value of an integrated ELISA system for the detection of 6 autoantibodies (ssDNA, dsDNA, Sm, RNP/Sm, SSA, and SSB). J Rheumatol. (1990) 17 (2): 192-200. Froelich C.J., et al.
  4. Diagnostic criteria for systemic lupus erythematosus: a critical review. J Autoimmun. (2014) 48-49: 10-3. Review. Yu C., et al.
  5. Anti-Sm and anti-RNP antibodies. Autoimmunity. (2005) 38 (1): 47-54. Review. Migliorini P., et al.
  6. The sensitivity and specificity of autoantibodies to the Sm antigen in the diagnosis of systemic lupus erythematosus. Ann Acad Med Singapore. (1998) 27 (1): 21-3. Pan L.T., et al.


  • Full Name: Sm Ab ELISA Kit
  • Reactivity: Human
  • Sample Type: Serum, Plasma
  • Sensitivity: 1.0 U/ml



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