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New Perspectives on New
(and Old)
Rheumatology Serologies
Robert W. Lightfoot, Jr., MD
Topics for Today’s Talk
1. The Old ANA
- What are the upper limits of normal for the ANA?
2. The New ANA (The Bead Assays)
- The problem of the false negative ANA
- The problem of the false positive ANA
3. The “ANA Profile” and Its Problems
4. The anti- CCP in Arthritis Diagnosis
Case #2
A 33 yr. old woman comes by the booth of the local lupus society at a health fair in your local shopping mall to be screened for SLE.
A 33 yr. old woman is referred
to you with 4 mos. of sustained
pain, stiffness and swelling in
the knuckles of the hand, the
wrists and the knees.
PE corroborates same and is
otherwise negative.
She is Normal Rheumatoid Arthritis
Case #1
Her ANA is + at 1:160Her ANA is + at 1:160
The most likely diagnosis is: The most likely diagnosis is:
What are the upper limits of
normal for the ANA?
The Bell Curve
2 S.D. 2 S.D.1 S.D. 1 S.D.
68% 2.5% 2.5%
The ANA
Hospital personnel, medical students 1%
Blood donors 3%
Elderly 10-15%
Miscellaneous diseases 6%
Arthritis, excluding RA, SLE 14%
Hospitalized, non-rheumatic 17%
Conn. Tissue diseases, not SLE 24%
Rheumatoid arthritis 30-40%
Relatives of SLE patients 33%
SLE 95%
uu uuuu1:20 1:40 1:80 1:160 1:320 1:640 1:1280
u
INDIRECT IF(IIF) ASSAY
HEP-2 CELL
PATIENT
SERUM
Fluorescein-tagged
anti-IgG, -IgA or -
IGM
ANA’S
There are between 100- 150
different antigens in the nucleus
that can be detected in the IIF ANA.
We only know what about 8 of those
antigens are.
What does an ANA of 1:160 tell
you?
Disease Present Disease Absent
Test Sensitivity & Specificity
SLE Present SLE Absent
ANA
95%+
97%Neg.
The ANA in Normals
ANA 1:40 positive
ANA 1:80 positive
ANA 1:160 positive
ANA 1:320 positive
Tan, EM, et al. Arthritis Rheum, 1997. 40:1601-1611.
Specificity
68.3%
86.7%
95%
96.7%
31.7%
13.3%
5%
3.3%
The Problem Is...
Lupus occurs in only 0.05% of the
general population
Ergo, 99.95% do not have lupus
SLE Present General Population
ANA Sensitivity & Specificity
97% Neg.
So...
Of the 0.05% of people who have SLE, 95% have a + ANA, or
0.0475% of people
Of the 99.95% of non-SLE, 3% have a + ANA, or
2.999% of people
2.999 / 0.0475 = 63/1
A ratio of 63:1:: Normal:SLE, i.e.,
98% of ANA positives do NOT have SLE
NOW…
Rheumatoid arthritis is
present in 1.5% of the
population
And, So...
Of the 1.5% of people who have RA, 30% are ANA + , or 0.45% of people,
Therefore,
The ratio of RA to SLE with positive ANA’s is:
0.45/0.0475, or >9 ANA + RA patients for every 1 ANA + SLE patient
And…
We could do similar calculations
for any pre-test percentage
likelihood a given patient has
lupus
SLE Present General Population
ANA Sensitivity & Specificity
97% Neg.
SLE Present General Population
ANA Sensitivity & Specificity
97% Neg.
SLE Present General Population
ANA Sensitivity & Specificity
97% Neg.
SLE Present General Population
ANA Sensitivity & Specificity
97% Neg.
Test Sensitivity & Specificity
SLE Present SLE Absent
ANA
95%+
97%Neg.
ANA PREDICTIVE VALUE FOR SLE
0%
20%
40%
60%
80%
100%
0% 20% 40% 60% 80% 100%
Pre-Test Probability
Po
st-T
est
Pro
ba
bil
ity
ANA +
ANA -
Sensitivity 95%, Specificity 97%
How can the ANA be
made more useful?
ANA PREDICTIVE VALUE
0%
20%
40%
60%
80%
100%
0% 20% 40% 60% 80% 100%
Pre-Test Probability
Po
st-T
est
Pro
ba
bil
ity
ANA +
ANA -
Sensitivity 95%, Specificity 97%
Every historical feature, every
physical finding (or lack
thereof) has its own sensitivity
and specificity for a given
illness.
At the end of the history and
physical exam, 98% of the
diagnostic testing has been
done.
Of the remainder, 98% of the
talent and wisdom required
is for differential diagnosis.
THE BEAD ASSAYS*
*ANA Choice
ANA Direct
Polystyrene microparticles of uniform size are used
as the solid phase.
SOLID-PHASE IMMUNOASSAYS
HISTONE SSA“n-DNA”
SSB SCL-70 RNP
SMITH
Unique bead sets can be conjugated with various, unique target
molecules of interest.
RNPSSBSSA Scl70
Thousands of each bead set are combined to form a
multiplex bead suspension.
The bead suspension is added to the wells of the microplate.
If present, antibody from the test sera will bind to the
antigen-coated bead.
Anti-human Ig reporter “tags” bound antibody.
AtheNA Multi-Lyte System
RNPSSBSSA Scl70
If the patient possesses antibody to more than one bead set, all the
relevant beads will be labeled with antibody and then conjugate.
AtheNA Multi-Lyte System
RNPSSBSSA Scl70
Beads flow through the flow cell, one bead at a time.
• Beads flow through the flow cell and light scatter will determine
color of each bead and if it fluoresces.
• The other determines the amount of classification dyes…the color
of the bead set (i.e., the antigen)
• One laser identifies the amount of fluorescence on the surface.
This flow analysis of the beads occurs at a rate of up to 20,000
beads/per second.
THE BEAD ASSAY AND
FALSE POSITIVES
Risks of “Panel” Testing*
No. of tests Percent of Times One is
Abnormal
1 5%
2 10%
4 19%
6 26%
10 40%
20 64%
*Galen & Gambino- “Beyond Normality”, Wiley & Sons 1975
“The more tests performed
on a healthy subject, the
more likely is the discovery
of an abnormal result.”
Beyond Normality- Galen, RS,& Gambino R, Wiley, 1975
In some labs, if a single “bead
antigen” assay is positive, the ANA is
reported as “positive”
Clues are-
There is no “ANA titer”
There are no “ANA units”
THE BEAD ASSAY AND
FALSE NEGATIVE ANA’s
OTHER SOLID-PHASE IMMUNOASSAYS
HISTONE SSA“n-DNA”
SSB SCL-70 RNP
SMITH? ?
Lab Report
ANA PositivenDNA Negative
SSA Positive
SSB Negative
Scl-70 Negative
Smith Negative
RNP Negative
Lab Report
ANA NegativenDNA Negative
SSA Negative
SSB Negative
Scl-70 Negative
Smith Negative
RNP Negative
Lab Report
ANA (IIF) PositivenDNA Negative
SSA Positive
SSB Negative
Scl-70 Negative
Smith Negative
RNP Negative
THE BEAD ASSAY AND FALSE
POSITIVE ANTI-nDNA
THE BEAD ANTI-“nDNA” ASSAY
Anti- nDNA
• The biggest problem with all anti-nDNA
assays is contamination of the antigen
with single-stranded portions.
• Antibodies to single-stranded DNA are
less specific than the ESR.
F-Anti-IgGSLE Serum
+ +
Crithidia luciliae Tube Dilution anti-nDNA Assay
Kinetochore
Nucleus
1. Any ANA screening test should include an
indirect immunofluorescent ANA screen.
2. For any bead assay positive for anti- “n-
DNA”, a better assay (? Crithidiae) should
be performed.
3. Any patient with an antibody to a single
“bead” antigen (e.g., anti-SSA), should
probably see a specialist.
(IIF)
THE ANTI-CCP ASSAY
peptidyl
arginine
deiminase
(PAD)
Ca++
+ H20+ NH3
+ H+
Arginine
NH2
C=NH2+
NH
CH2
CH2
CH2
O
CN
H
C
Citrulline
NH2
NH
C=O
CH2
CH2
CH2
O
CN
H
C
Known Citrullinated Proteins
• Myelin basic protein
• Filaggrin
• Keratin
• Histones
• Vimentin
• Fibrinogens/fibrins
• Type I Collagen in synovium
CCP Peptides
SHQESTRGRSRGRSGRSGS (306-324)
SHQESTXGRSRGRSGRSGS ( “ - “ )
SHQESTRGXSRGRSGRSGS ( “ - “ )
SHQESTRGRSXGRSGRSGS ( “ - “ )
SHQESTXGRSXGRSGRSGS ( “ - “ )
Lee & SchurRF+
RF-
From, Lee, DM and Schur, PH, Ann Rheum Dis 2003 62:870.
False Positive anti-CCP TestsPsoriatic arthritis 8.6%
-Psoriasis sans arthritis 0.7-17%
SLE 7.8%
Sjogren’s 5.7%
Spondyloarthropathy 2.3%
Scleroderma 6.8%
Hep C Cryoglobulinemia 3.5%
Osteoarthritis 2.2%
Juvenile polyarthritis 7.7%
Fibromyalgia 2.7%
Tuberculosis 34.3%
Arthritis Rheum 61 (11): 1472, 2009
Anti-CCP Specificity and PPV
TEST
Pos.
Likelihood
Ratio
Neg.
Likelihood
Ratio
Sens. Spec.
RF 4.9 0.38 69% 85%
Anti-CCP 12.5 0.36 67% 95%
Prognostic Value of a-CCP’s
• Of 936 patients seen in an Early (<2yrs.)
Arthritis Clinic (EAC), 590 (63%) could
be readily diagnosed, and 205 (21.9%)
had RA.
• 346 (37%) had undifferentiated arthritis
(UA).
• They were followed for 3 years.
Van Gaalen, et al., A&R 50:709, 2004
Prognostic Value of a-CCP
Criterion ACR Criteria ACR & a-CCP
AM stiffness > 1hr. 2.9 ns
Arthritis of > 3 jts. 5.8 5.0
Symmetric arthritis 2.6 6.1
IgM RF positivity 9.8 ns
Erosions on x-ray 7.6 8.7
Anti-CCP positive N/A 38.6
(Odds Ratios in Multivariate Analysis)
Van Gaalen, et al.,A&R, 2004
RF > 50IU
RF < 50IU
Ero
sion
Sco
re
0 2 yrs1 yr 3 yrs
0
10
20
30
40
50
60
70
Nell, et al., Ann Rheum Dis 2005
A-CCP +
A-CCP -
Ero
sion
Sco
re
0 2 yrs1 yr 3 yrs
0
10
20
30
40
50
60
70
Nell, et al., Ann Rheum Dis 2005
ANA
RF
a-CCP
I
N
T
E
R
P
R
E
T
+
+
+
–
–
–
–
–
+
+
–
–
–
+
+
+
+
–
+
–
+
–
+
–
?SLE
M
O
R
E
T
E
S
T
S
RA
?SLE
M
O
R
E
T
E
S
T
S
?RAOther
?SLE
M
O
R
E
T
E
S
T
S
RA
?SLE
RA RA RARA
Summary
• If your ANA Panel shows a negative
ANA, make sure an IIF ANA is done.
• If your ANA is “positive” without a titer,
make sure an IIF ANA is done.
• If your ANA is positive at a titer of
<1:320, more history and/or a panel may
be indicated.
• A positive anti-nDNA usually isn’t.
• A positive anti-CCP is strong evidence
for RA