Home / Decoding the ANA: A Guide to ANA Testing
Website authors: Ashley Abbott, MD and Abigail L. Gilbert, MD, MSCI
When should I order an ANA?ANA testing is an important test when it is likely a patient has an autoimmune disease like systemic lupus erythematosus. Only order an ANA after careful clinical evaluation. This includes a thorough history and physical exam and sometimes basic labs such as a blood count, chemistry, and urine tests.
ANA testing pearls:
- An ANA should be ordered if you have a high suspicion for an autoimmune disease such as Sjogren’s, Lupus, or Scleroderma. (See table below.)
- ANA is NOT recommended in patients with fatigue, back pain, headaches, musculoskeletal pain, paresthesia, abdominal pain, or vague symptoms such as diffuse pain.
Autoimmune diseases associated with a positive ANA:
- A positive ANA does NOT need to be repeated!
- A positive ANA only indicates antibodies are present. It does NOT mean a patient has an autoimmune disease.
- If positive, additional testing for antigen specific antibodies should only be considered if presentation is consistent with an autoimmune disease.
- Serial ANA tests in autoimmune disease is NOT useful to monitor disease activity. The ANA will usually still be positive even when an autoimmune disease is well controlled.
- A negative ANA does NOT need to be repeated!
- If the ANA test is negative, do not order additional antibody testing.
- Repeating an ANA less than 12 months is almost always unnecessary (2).
- If an autoimmune condition such as lupus is suspected, then more lab tests can be helpful. Consider checking the following:
- CBC with differential
- CMP
- Urinalysis and Urine/Protein ratio
- dsDNA
- ENA
- C3 and C4 complements
The level at which the sample is diluted with a recognizable stain is the ANA titer. The clinical significance of ANA titers can be difficult to assess. Up to 30% of healthy individuals have a positive ANA of 1:40 or greater. Higher ANA titers are more likely to be clinically significant. In one study analyzing ANA titers in patients with confirmed autoimmune diseases, the median ANA titer was 1:320 (3).
In one study, Tan et. el found the following (9):
Careful consideration must be placed in interpreting an ANA test. A positive test does NOT denote the presence of an autoimmune disease!
Counseling a patient with a positive ANA can be challenging since this result can often be misinterpreted. Proper counseling is essential in helping the patient understand the results. They also need you to guide them through the next steps. It is important to let a patient know that the positive result only indicates an antibody is present. Emphasize that a positive test result can also be positive in healthy individuals. Apositive ANA test alone does NOT diagnose a specific autoimmune disease. Sometimes further investigation is indicated if there are symptoms suggestive of an autoimmune disease.
Patients need to know that a positive test result can also be seen in healthy individuals.If there is high concern for an autoimmune disorder, discuss the disease you are considering. Sometimes further testing and consultation with a rheumatologist can help determine the underlying cause. Patients with a positive ANA who do not have symptoms of an autoimmune disease do NOT need to see a rheumatologist.
If there is low concern for an autoimmune condition, it is important to address the patient’s fears and anxieties while providing reassurance that a positive test result does not mean the patient has a new diagnosis.
Given that 15-20% of healthy individuals have a positive ANA, it is challenging to diagnose rheumatologic disorders. In a cross-sectional analysis, the prevalence a of positive ANA increased with age (P = 0.01) and were more prevalent among females than males (17.8% vs 9.6%,P < 0.001). The prevalence is also higher in African Americans compared to Caucasians (adjusted prevalence odds ratio 1.30, 95% CI 1.00 to 1.70) (4). Hence, there are demographic variables that can affect positivity which may not be accounted for in ANA interpretation.
Healthcare costs continue to rise. ANA screening can have a high background positivity rate in the general population. When ANA is checked for vague symptoms, it can lead to misdiagnosis and additional testing which is often not helpful. In a retrospective study, more than 90% of patients who were referred to an academic rheumatology clinic for a positive ANA had no evidence of an ANA-associated rheumatic disease (5). Consequently, inappropriate ANA testing places a strain on healthcare resources and undue anxiety for patients.
ANA antibodies can be seen in up to 20% of healthy adults. ANA antibodies can bind and damage certain structures within a cell’s nucleus (1). ANA antibodies are not specific and can be seen in many autoimmune diseases. ANA can also be positive in other conditions including infections (eg tuberculosis, endocarditis, HIV, Hepatitis C, EBV), malignancy, and lymphoproliferative disorders.
Conclusion- Consider ordering an ANA if a patient has signs or symptoms of lupus, Sjogren’s, or scleroderma.
- An ANA should not be ordered for headaches, diffuse pain, back pain, fatigue, diffuse pain, or vague complaints without other symptoms.
- A positive ANA is not sufficient for diagnosing lupus or other autoimmune diseases.
- 20% of health adults can have a positive ANA.
- If an ANA is positive, it should be interpreted using the context of specific symptoms and clinical findings (ie skin tightening, lupus rashes, inflammatory arthritis, oral or nasal ulcers, alopecia, cytopenia, etc).
- Only check additional antibodies if the ANA is positive.
- Do NOT repeat an ANA test.
You can contact Dr. Gilbert with further questions about ANA testing: (email: abigail.gilbert@unc.edu)
- Kumar Y, Bhatia A, Minz RW. Antinuclear antibodies and their detection methods in diagnosis of connective tissue diseases: a journey revisited. Diagn Pathol. 2009 Jan 2;4:1. doi: 10.1186/1746-1596-4-1. PMID: 19121207; PMCID: PMC2628865.
- Abeles AM, Abeles M. The clinical utility of a positive antinuclear antibody test result. Am J Med. 2013 Apr;126(4):342-8. doi: 10.1016/j.amjmed.2012.09.014. Epub 2013 Feb 8. PMID: 23395534.
- Wei Q, Jiang Y, Xie J, Lv Q, Xie Y, Tu L, Xiao M, Wu Z, Gu J. Analysis of antinuclear antibody titers and patterns by using HEp-2 and primate liver tissue substrate indirect immunofluorescence assay in patients with systemic autoimmune rheumatic diseases. J Clin Lab Anal. 2020 Dec;34(12):e23546. doi: 10.1002/jcla.23546. Epub 2020 Oct 13. PMID: 33047841; PMCID
- Dinse GE, Parks CG, Weinburg CR, Meier HCS, Co CA, Chan L, Miller F, Antinuclear Antibodies and mortality in the National Health and Nutrition Examination Survey (1999-2004). PLoS One 2017:12:20185977
- Narain S, Richards HB, Satoh M, et al. Diagnostic accuracy for lupus and other systemic autoimmune diseases in the community setting. Arch Intern Med. 2004;164:2435-2441.
- Satoh M, Vázquez-Del Mercado M, Chan EK. Clinical interpretation of antinuclear antibody tests in systemic rheumatic diseases. Mod Rheumatol. 2009;19(3):219-28. doi: 10.1007/s10165-009-0155-3. Epub 2009 Mar 10. PMID: 19277826; PMCID: PMC2876095.
- Tan EM, Feltkamp TE, Smolen JS, Butcher B, Dawkins R, Fritzler MJ, Gordon T, Hardin JA, Kalden JR, Lahita RG, Maini RN, McDougal JS, Rothfield NF, Smeenk RJ, Takasaki Y, Wiik A, Wilson MR, Koziol JA. Range of antinuclear antibodies in “healthy” individuals. Arthritis Rheum. 1997 Sep;40(9):1601-11. doi: 10.1002/art.1780400909. PMID: 9324014.
- Tan EM, Feltkamp TE, Smolen JS, Butcher B, Dawkins R, Fritzler MJ, Gordon T, Hardin JA, Kalden JR, Lahita RG, Maini RN, McDougal JS, Rothfield NF, Smeenk RJ, Takasaki Y, Wiik A, Wilson MR, Koziol JA. Range of antinuclear antibodies in “healthy” individuals. Arthritis Rheum. 1997 Sep;40(9):1601-11. doi: 10.1002/art.1780400909. PMID: 9324014.
