A 3-year-old girl has had a swollen, stiff left knee and right ankle for 10 weeks, without fever, rash or eye symptoms, and is diagnosed with oligoarticular juvenile idiopathic arthritis. Results: HEp-2 ANA 1:320, speckled; anti-dsDNA negative; ENA panel (Sm, RNP, SSA, SSB, Scl-70, Jo-1) negative; rheumatoid factor negative; anti-CCP negative; HLA-B27 negative; CRP 9 mg/L (reference < 5 mg/L); CBC, urinalysis, C3 and C4 within reference intervals. What is the main clinical significance of her ANA result?

A high risk of silent anterior uveitis

Future RF-positive, adult-type arthritis

Early systemic lupus erythematosus

Likely enthesitis-related arthritis

A 58-year-old man with chronic hepatitis C has leg purpura, joint pain and proteinuria. RF is 480 IU/mL (reference < 15), anti-CCP is negative, C4 is very low and C3 is mildly low. The most likely explanation is:

IgA vasculitis (Henoch-Schonlein)

Seropositive rheumatoid arthritis

Thyroglobulin antibodies are measured with every serum thyroglobulin used to monitor differentiated thyroid cancer. Why?

They can make immunometric thyroglobulin results falsely low

They show whether the patient also has Graves disease

They are needed to adjust thyroglobulin for the TSH level

They make immunometric thyroglobulin results falsely high

ANA, thyroid antibodies and rheumatoid factor

10 ASCP MLS practice questions on ANA, thyroid antibodies and rheumatoid factor, part of Immunology. The first 10 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A 3-year-old girl has had a swollen, stiff left knee and right ankle for 10 weeks, without fever, rash or eye symptoms, and is diagnosed with oligoarticular juvenile idiopathic arthritis. Results: HEp-2 ANA 1:320, speckled; anti-dsDNA negative; ENA panel (Sm, RNP, SSA, SSB, Scl-70, Jo-1) negative; rheumatoid factor negative; anti-CCP negative; HLA-B27 negative; CRP 9 mg/L (reference < 5 mg/L); CBC, urinalysis, C3 and C4 within reference intervals. What is the main clinical significance of her ANA result?
1. AFuture RF-positive, adult-type arthritis
2. BEarly systemic lupus erythematosus
3. CLikely enthesitis-related arthritis
4. DA high risk of silent anterior uveitis
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Answer: D · A high risk of silent anterior uveitis
In young girls with oligoarticular JIA, a positive ANA is the strongest laboratory marker of risk for chronic anterior uveitis. This uveitis is usually painless, with no red eye, and can scar the eye and reduce vision before anyone notices, so ANA-positive children have slit-lamp eye screening every few months. In JIA the ANA is a risk marker, not a sign of lupus, which the negative dsDNA and ENA panel, normal urine and normal complement also argue against. Negative RF and anti-CCP make an adult-type seropositive polyarthritis unlikely. Enthesitis-related arthritis is linked to HLA-B27 and to acute, painful uveitis, mostly in older boys.
- A: RF and anti-CCP are both negative, so seropositive adult-type disease is unlikely.
- B: Negative dsDNA and ENA, normal urine and normal complement argue against lupus.
- C: Enthesitis-related arthritis goes with HLA-B27, which is negative, and usually affects older boys.
Question 2 · Hard
A 58-year-old man with chronic hepatitis C has leg purpura, joint pain and proteinuria. RF is 480 IU/mL (reference < 15), anti-CCP is negative, C4 is very low and C3 is mildly low. The most likely explanation is:
1. ASystemic lupus erythematosus
2. BMixed cryoglobulinemia
3. CIgA vasculitis (Henoch-Schonlein)
4. DSeropositive rheumatoid arthritis
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Answer: B · Mixed cryoglobulinemia
In hepatitis C, B cells often make an IgM with RF activity that binds IgG to form cold-precipitating immune complexes (type II or III mixed cryoglobulins). These complexes deposit in small vessels, causing purpura, joint pain and membranoproliferative glomerulonephritis, and they consume early complement, so C4 is typically very low. A high RF with a negative anti-CCP fits, because RF is not specific for rheumatoid arthritis. The sample for cryoglobulins must be kept at 37 °C until the serum is separated.
- A: SLE is diagnosed with ANA and dsDNA antibodies; hepatitis C with a high RF and very low C4 fits cryoglobulinemia better.
- C: IgA vasculitis has normal complement and no high RF.
- D: Rheumatoid arthritis is unlikely with negative anti-CCP, purpura and nephritis in hepatitis C.
Question 3 · Medium
On HEp-2 cells, an ANA stains interphase nuclei evenly and also stains the condensed chromosomes of dividing cells. Antibodies to which antigens are most likely?
1. ASm and U1-RNP
2. BFibrillarin and PM/Scl
3. CSS-A/Ro and SS-B/La
4. DdsDNA, histones or nucleosomes
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Answer: D · dsDNA, histones or nucleosomes
A homogeneous pattern with stained metaphase chromatin means the antibody targets chromatin itself: dsDNA, histones or nucleosomes. It is common in SLE and drug-induced lupus. Antibodies to Sm, RNP, SS-A and SS-B target the nucleoplasm and give speckled patterns with an unstained chromosome plate. The specific antibody is then identified with dsDNA, histone or ENA tests.
- A: Sm and U1-RNP give a coarse speckled pattern with unstained chromosomes.
- B: Fibrillarin and PM/Scl give a nucleolar pattern.
- C: SS-A and SS-B give a fine speckled pattern with unstained chromosomes.
Question 4 · Easy
Rheumatoid factor is most often an IgM antibody that binds:
1. ACitrullinated peptides
2. BDouble-stranded DNA
3. CThe Fab portion of human IgG
4. DThe Fc portion of human IgG
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Answer: D · The Fc portion of human IgG
Rheumatoid factor is an autoantibody, usually IgM, against the Fc region of the patient's own IgG. Latex and nephelometric RF tests use particles or complexes carrying IgG, which the IgM RF links together. RF is found in most patients with rheumatoid arthritis but also in Sjogren syndrome, hepatitis C, chronic infections and healthy older adults. Anti-CCP is the more specific test for rheumatoid arthritis.
- A: Antibodies to citrullinated peptides are anti-CCP, a separate test.
- B: Antibodies to dsDNA are linked to SLE, not to RF.
- C: The Fab region holds the antigen-binding site; RF binds the Fc region.
Question 5 · Medium
Thyroglobulin antibodies are measured with every serum thyroglobulin used to monitor differentiated thyroid cancer. Why?
1. AThey show whether the patient also has Graves disease
2. BThey are needed to adjust thyroglobulin for the TSH level
3. CThey make immunometric thyroglobulin results falsely high
4. DThey can make immunometric thyroglobulin results falsely low
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Answer: D · They can make immunometric thyroglobulin results falsely low
About a quarter of patients with differentiated thyroid cancer have thyroglobulin antibodies. In two-site immunometric assays these antibodies bind thyroglobulin and block the capture or detection antibody, giving falsely low or undetectable results that can hide a recurrence. Labs therefore measure the antibodies in the same sample as every thyroglobulin. When antibodies are present, a low thyroglobulin cannot be trusted, and the antibody trend is followed as well.
- A: Graves disease is identified by TSH receptor antibodies.
- B: Thyroglobulin is read with the TSH status in mind, but that is not why antibodies are measured.
- C: Immunometric assays are biased low, not high, by these antibodies.
Question 6 · Hard
A woman treated with radioactive iodine for Graves disease 3 years ago is now 22 weeks pregnant and euthyroid on levothyroxine. Which test best predicts the risk of fetal or neonatal hyperthyroidism?
1. AThyroglobulin antibodies
2. BTSH receptor antibodies
3. CThyroid peroxidase antibodies
4. DMaternal serum TSH
Answer and explanation in LearnFree account
Question 7 · Medium
A HEp-2 ANA shows bright staining of the nucleoli, with little staining of the rest of the nucleus. This pattern is most closely linked to:
1. ADrug-induced lupus
2. BSystemic sclerosis
3. CMixed connective tissue disease
4. DRheumatoid arthritis
Answer and explanation in LearnFree account
Question 8 · Hard
A healthy 32-year-old woman has a HEp-2 ANA of 1:640 with a dense fine speckled nuclear pattern. The chromosomes of dividing cells also stain strongly. Tests for dsDNA and ENA antibodies are negative. The best interpretation is:
1. ADrug-induced lupus from antihistone antibodies
2. BProbable anti-DFS70, common in healthy people
3. CSjogren syndrome with undetectable SS-A antibody
4. DEarly SLE that needs monthly dsDNA testing
Answer and explanation in LearnFree account
Question 9 · Hard
A 56-year-old woman has itching, fatigue and ALP 410 U/L [6.8 µkat/L] (reference 40-130 U/L [0.67-2.17 µkat/L]) with normal bilirubin. Her HEp-2 ANA shows no nuclear staining but coarse granular staining across the cytoplasm. Which antibody is most likely?
1. AAnti-smooth muscle (F-actin) antibody
2. BAnti-ribosomal P antibody
3. CAnti-Jo-1 antibody
4. DAnti-mitochondrial antibody
Answer and explanation in LearnFree account
Question 10 · Medium
Which ANA immunofluorescence pattern is linked to anti-centromere antibodies and limited cutaneous systemic sclerosis (CREST)?
1. APeripheral (rim) pattern
2. BHomogeneous pattern
3. CNucleolar pattern
4. DDiscrete speckled pattern
Answer and explanation in LearnFree account

ANA, thyroid antibodies and rheumatoid factor

A 58-year-old man with chronic hepatitis C has leg purpura, joint pain and proteinuria. RF is 480 IU/mL (reference < 15), anti-CCP is negative, C4 is very low and C3 is mildly low. The most likely explanation is:

On HEp-2 cells, an ANA stains interphase nuclei evenly and also stains the condensed chromosomes of dividing cells. Antibodies to which antigens are most likely?

Rheumatoid factor is most often an IgM antibody that binds:

Thyroglobulin antibodies are measured with every serum thyroglobulin used to monitor differentiated thyroid cancer. Why?

A woman treated with radioactive iodine for Graves disease 3 years ago is now 22 weeks pregnant and euthyroid on levothyroxine. Which test best predicts the risk of fetal or neonatal hyperthyroidism?

A HEp-2 ANA shows bright staining of the nucleoli, with little staining of the rest of the nucleus. This pattern is most closely linked to:

A healthy 32-year-old woman has a HEp-2 ANA of 1:640 with a dense fine speckled nuclear pattern. The chromosomes of dividing cells also stain strongly. Tests for dsDNA and ENA antibodies are negative. The best interpretation is:

A 56-year-old woman has itching, fatigue and ALP 410 U/L [6.8 µkat/L] (reference 40-130 U/L [0.67-2.17 µkat/L]) with normal bilirubin. Her HEp-2 ANA shows no nuclear staining but coarse granular staining across the cytoplasm. Which antibody is most likely?

Which ANA immunofluorescence pattern is linked to anti-centromere antibodies and limited cutaneous systemic sclerosis (CREST)?