4 AUTOIMMUNE DISEASES Flashcards
(1) What is a general definition for autoimmunity?
A. Increase of tolerance to self-antigens
B. Loss of tolerance to self-antigens
C. Increase in clonal deletion of mutant cells
D. Manifestation of immunosuppression
B. Loss of tolerance to self-antigens
Autoimmunity is a loss of tolerance to self-antigens and the subsequent formation of autoantibodies.
(2) An ANA test is performed on a specimen from a 55-year-old woman who has unexplained joint pain. The IFA result shows a titer of 40 and a homogeneous pattern. The appropriate follow-up for this patient is:
A. Anti-DNA assay
B. Extractable nuclear antigen (ENA) testing
C. Retest ANA in 3 to 6 months
D. CH50 complement assay
C. Retest ANA in 3 to 6 months
Approximately 25% of women in this age range may have low titer–positive ANA assays with no demonstrable connective tissue disease. A patient with anti-DNA–positive SLE would be expected to have a much higher titer (greater than 160) in an IFA. A similar titer would be expected for an ENA positive specimen, although the pattern would be speckled. Complement testing would not be indicated with this low titer in a 55-year-old female.
(3) Which disease is likely to show a rim (peripheral) pattern in an immunofluorescence (IF) microscopy test for ANA?
A. Mixed connective tissue disease (MCTD)
B. RA
C. SLE
D. Scleroderma
C. SLE
The rim or peripheral pattern seen in indirect immunofluorescence techniques is most commonly found in cases of active SLE. The responsible autoantibody is highly correlated to anti–double stranded DNA (anti-dsDNA).
(4) A patient’s specimen is strongly positive in an ANA ELISA. Which of the following would not be an appropriate follow-up to this result?
A. IFA on human epithelial type 2 (HEp-2) cells
B. Specific ENA ELISA tests
C. Specific anti-DNA ELISA
D. Rheumatoid factor (RF) assay
D. Rheumatoid factor (RF) assay
The ANA ELISA is a screening assay. A positive result may be followed up by more specific antibody ELISA tests or an ANA IFA to determine pattern and titer. The ANA ELISA does not screen for RF.
(5) What type of antibodies is represented by the homogeneous pattern in the IFA for ANAs?
A. Antihistone antibodies
B. Anticentromere antibodies
C. Anti-ENA (anti-Smith [anti-Sm] and anti ribonucleoprotein [anti-RNP]) antibodies
D. Anti-RNA antibodies
A. Antihistone antibodies
Antihistone antibodies (and also anti-DNA antibodies) cause the solid or homogeneous pattern, which is commonly found in patients with SLE, RA, MCTD, and Sjögren syndrome. Antibodies to the centromere of chromosomes is a marker for the CREST (calcinosis, Raynaud phenomenon, esophageal dysfunction, sclerodactyly, and telangiectasia) form of systemic sclerosis.
(6) What disease is indicated by a high titer of anti Sm antibody?
A. MCTD
B. RA
C. SLE
D. Scleroderma
C. SLE
High titer anti-Sm is indicative of SLE. Anti-Sm is an antibody against saline ENAs and causes a speckled pattern of immunofluorescence.
(7) Which disease is least likely when a nucleolar pattern occurs in an IFA for ANAs?
A. MCTD
B. Sjögren syndrome
C. SLE
D. Scleroderma
A. MCTD
All of the diseases except MCTD may cause a nucleolar pattern of immunofluorescence. Nucleolar fluorescence is caused by anti-RNA antibodies and is seen in about 50% of patients with scleroderma.
(8) What antibodies are represented by the nucleolar pattern in the IFA for ANAs?
A. Antihistone antibodies
B. Anti-dsDNA antibodies
C. Anti-ENA (anti-Sm and anti-RNP) antibodies
D. Anti-RNA antibodies
D. Anti-RNA antibodies
Anti-RNA antibodies are represented by the nucleolar pattern. This pattern may be seen in most systemic autoimmune diseases and is especially common in patients with scleroderma. Anti-RNA and anti-Sm are not usually found in patients with MCTD. This is a syndrome involving aspects of SLE, RA, scleroderma, and polymyositis. The immunofluorescence pattern most often seen in MCTD is the speckled pattern caused by anti-RNP.
(9) Which test would best distinguish between SLE and MCTD?
A. Multiplex or ELISA test for anti-Sm and anti-RNP
B. IFA using Crithidia as substrate
C. Slide agglutination testing
D. Laboratory tests cannot distinguish between these disorders
A. Multiplex or ELISA test for anti-Sm and anti-RNP
Line blots, multiplex, and ELISA assays, using purified or recombinant antigens, are available for differentiating anti-RNP from anti-Sm. Anti-Sm with or without anti-RNP is found in approximately one third of patients with SLE. Anti-RNP in the absence of anti-Sm is found in over 95% of patients with MCTD.
(10) An ANA test on HEp-2 cells shows nucleolar staining in interphase cells and dense chromatin staining in mitotic cells. The most likely cause of this staining pattern is:
A. Antifibrillarin antibody
B. Anti–ribosomal P antibody
C. A serum with nucleolar and homogeneous patterns
D. Technical artifact
A. Antifibrillarin antibody
Antifibrillarin antibody has this appearance. Ribosomal P antibody has nucleolar staining and a background homogeneous and cytoplasmic stain. A combination nucleolar/homogeneous specimen will also show homogeneous staining in the interphase cells. This pattern is not seen in typical technical artifacts.
(11) Which immunofluorescence pattern indicates the need for ENA testing by multiplex, line blots, or ELISA assays?
A. Homogeneous or solid
B. Peripheral or rim
C. Speckled
D. Nucleolar
C. Speckled
A speckled pattern is often caused by the presence of antibodies against the ENAs, such as Sm, RNP, SSA, and SSB. Homogeneous and rim patterns suggest antibodies to dsDNA. The homogeneous pattern may also be seen with antibodies to deoxyribonuclear protein, which is not an ENA. Nucleolar patterns often indicate antibodies to RNA or fibrillarin.
(12) Which of the following is used in rapid slide tests for detection of RFs?
A. Whole IgM molecules
B. Fc portion of the IgG molecule
C. Fab portion of the IgG molecule
D. Fc portion of the IgM molecule
B. Fc portion of the IgG molecule
RFs react with the Fc portion of the IgG molecule and are usually IgM. This is the basis of rapid agglutination tests for RA. Particles of latex or cells are coated with IgG. Addition of serum containing RF results in visible agglutination.
(13) Which of the following methods is least likely to give a definitive result for the diagnosis of RA?
A. Nephelometric measurement of anti-IgG
B. Agglutination testing for RF
C. Anti-CCP
D. IFA for ANAs
D. IFA for ANAs
Patients with RA often show a homogeneous pattern of fluorescence in tests for ANAs. However, this pattern is seen in a wide range of systemic autoimmune diseases and in many normal persons at a titer below 10. The first two methods listed may be used to identify anti-IgG, which is one laboratory criterion used to establish a diagnosis of RA. Anti CCP is an additional laboratory criterion used in the RA diagnostic algorithm.
(14) Which disease might be indicated by antibodies to smooth muscle?
A. Atrophic gastritis
B. Autoimmune hepatitis
C. Myasthenia gravis
D. Sjögren syndrome
B. Autoimmune hepatitis
Antibodies to smooth muscle are found in the serum of up to 70% of patients with active chronic hepatitis and up to 50% of patients with primary biliary cirrhosis.
(15) Antibodies to thyroid peroxidase may appear in which of the following diseases?
A. Graves disease and Hashimoto thyroiditis
B. Myasthenia gravis
C. Granulomatous thyroid disease
D. Addison disease
A. Graves disease and Hashimoto thyroiditis
Antibodies to thyroid peroxidase may be detected in both Graves disease (hyperthyroidism) and Hashimoto thyroiditis (hypothyroidism). If a positive result is found to thyroid peroxidase, thyroxine levels and clinical presentation can be used to distinguish between the two diseases.
