Transcript Rheumatology_Laboratory_Talk

RHEUMATIC DISEASE
LABORATORY TESTING
BASICS OF LAB TEST
ORDERING
Intent:
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Establish a diagnosis
Determine prognosis
Monitor disease activity
Indicate organ
involvement
Monitor stage of disease
Indicate disease
mechanisms
Guide treatment
Monitor toxicity
Pitfalls:
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Misdiagnosis
Permanent labeling of
patient
Needless additional
testing
Inappropriate therapy
and/or referral
Expense
Overlooking the correct
diagnosis
NEEDLESS ANXIETY
FOR PATIENT!!!
BASICS OF LAB TEST
ORDERING
“We checked
an ANA, ESR,
& RF to look
for connective
tissue
disease…..”
TWO BY TWO TABLE
DIS
(+)
DIS
(-)
TEST
(+)
A
(TP)
B
(FP)
PPV =
A/A+B
TEST
(-)
C
(FN)
D
(TN)
NPV =
D/C+D
SENS =
SPEC =
TP/TP+FN TN/FP+TN
DISEASE PREVALENCE &
PREDICTIVE VALUES
SNOUT
A test with high
SeNsitivity is excellent
For ruling OUT a dx…
“SNOUT”
Sensitivity is true pos
over true pos plus
false negatives
SPIN
A test with a high
SPecificity is great for
Ruling IN a dx
“SPIN”
Specificity is true
negative over true
negative plus false
positive
TYPES OF LABS
1. High sensitivity labs - SNOUT:
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good for “screening” or “ruling out”
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ESR (inflammation)
ANA (lupus – but NOT “CTD”)
2. High specificity labs - SPIN:
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good for “diagnosing” or “ruling in”
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ds-DNA (lupus)
Scl-70 (PSS)
Jo-1 (ILD in polymyositis)
C-ANCA (WG)
TYPES OF LABS
3. Disease activity labs:
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How is treatment working ?
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CPK
complement levels (lupus)
ds-DNA (lupus)
ESR, CRP (RA, GCA, PMR)
4. Prognosis labs:
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Should I be aggressive early with meds?
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RF (RA)
ds-DNA antibody (SLE)
Citrulline antibody (RA)
“THE NET”
– looking for organ
damage and mimickers
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UA with micro
 glomerulonephritis
CBC
 anemia chronic disease
Lipids
 accelerated atherogenesis w/ inflammation
Hep B & Hep C
 extrahepatic disease features.
TSH
CPK
Chem Panel and LFT’s
? Vitamin D (fibromyalgia)
ESR
ESR
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The king of non-specific lab tests but
very sensitive
Infection / malignancy/CTD all raise the
ESR
Westergren method used at NMCSD (up
to 120 mm/hr)
Useful for “ruling out” systemic
inflammatory disease
ESR
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Non-inflammatory factors that raise ESR
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Aging
Female Sex
Obesity
Pregnancy
Anemia
Markedly Low ESR (0 mm/hr)
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Afribinogenemia/dysfibrinogenemia
Agammaglobulinemia
Extreme polycythemia (HCT > 65)
Increased plasma viscosity
ESR
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Adjunctive Testing
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Good history and physical
Repeat test 1-3 mo? Prior ESRs?
CRP
SPEP, Quantitative Immune Globulins
Age Appropriate Malignancy Screen
CRP
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(“Can’t refuse prednisone”)
Produced as an acute-phase reactant by the liver in response to IL-6
and other cytokines
Seen in sera of patients with pneumococcal pneumonia in 1930
(protein could precipitate C-polysaccharide of pneumococcus)
Can recognize phosphocholine, other phospholipids
Can activate complement (classic)
Can bind to and modulate the behavior of phagocytic cells in both pro
and anti-inflammatory ways
Quicker rise and fall than ESR
Sensitive but not diagnostic of any particular condition
“CRP rises with infection and ESR rises with CTD’s….” (not always
true!!!)
Normal less than 1.0 mg/dl
> 8-10 mg/dl, think bacterial infection, systemic vasculitis, or widely
metastatic cancer
CRP
OTHER ACUTE PHASE
REACTANTS
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Polyclonal Immunglobulins (SPEP)
Alkaline phosphatase
Transaminases
Fibrinogen
Haptoglobin
Serum amyloid A
Platelet count
Ferritin
Alpha-1 antitrypsin
Decreased albumin (“negative” APR)
COMPLEMENT
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A system of interacting serum proteins that function
sequentially as initiators, regulators, and effectors of
cell lysis and inflammation
Provide innate defense against microbes and a
“complement” to humoral immunity
Biologic cascade in which, by limited proteolysis, one
component activates the next, causing rapid and
robust amplification of the system
Critical to normal processing of immune complexes
Causes host tissue damage in antibody-mediated
autoimmune syndromes
COMPLEMENT
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Measurement useful if:
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concern for inherited deficiency states
which can pre-dispose to infectious and
rheumatic syndromes
immune-complex mediated disease
COMPLEMENT
COMPLEMENT
CLASSICAL:
ALTERNATIVE:
Ag-Ab
complexes
such as SLE
Endotoxin
IgA
Drugs
COMPLEMENT
COMPLEMENT REGULATION
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C1 inhibitor – [prevents C1s from activating
C4 and C2]
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deficiency -> hereditary angioneurotic edema
and chronic C4 activation/consumption with
resulting low C4
C3 and C4 nephritic factors
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Autoantibodies against alternative and classical
pathway C3 convertases, respectively
Stabilizes antibody, increasing half-life causing
excessive C3 cleavage
Secondary deficiency of C3
ROUTINE COMPLEMENT
LEVEL TESTING
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CH 50
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C3
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useful screen for BOTH classic and alternative
pathways
C4
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reflects a functionally intact classic pathway; good
screen for deficiency state (C1-9)
depressed with activation of classic pathway or in
patients with angioneurotic edema
C5-9
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terminal attack complex
DIMINISHED COMPLEMENT
LEVELS
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partial or complete inherited deficiency
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C1q inhibitor deficiency -> hereditary angioedema
and low C4
C2 or C4 deficiency -> SLE
C3 deficiency -> recurrent infections (bacterial)
C5a inhibitor deficiency -> FMF
C5-9 deficiency -> recurrent neisserial infxn
immune complex consumption
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(SLE / post-strep GN, cryoglobulinemia, SBE,
membranoproliferative GN, Sjogren’s, other
vasculitides)
RHEUMATOID FACTOR
RHEUMATOID FACTOR
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Hemagglutinating
activity noted in 1940,
associated with RA in
1949
Heterogeneous family
of IgM abys directed
against IgG
RF response transiently
associated with many
infectious diseases (TB,
SBE, syphillis, HCV)
RF response more
permanent with chronic
diseases
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1-4% of healthy whites,
10-25% age > 70 ,
30% some NA Indians
80% of RA pts (+)
80-90% of SS (+)
70% of chronic HCV (+)
Both Types II and III
cryoglobulins
worse prognosis and
more aggressive RA
Not specific for RA
No correlation with
RA disease activity
RHEUMATOID FACTOR
RHEUMATOID FACTOR
Elevated RF (ChRONIC immune
stimulation)
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Ch- chronic disease (esp hepatic and
pulmonary)
R- rheumatoid arthritis
O- other connective tissue disease
N- neoplasms (lymphoproliferative
diseases, esp after XRT, chemo)
I – Infections
C - cyroglobulins
ANTI-CITRULLINE AB
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ELISA available against CCP (cyclic
citrullinated peptide) – one of the antifilaggrin antibodies
Very specific, not very sensitive (SPIN)
Utility may be in defining early and
aggressive RA, prior to development of RF
Useful in RF (+) positive conditions that
mimic RA
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Sjogren’s
Hep C
cryoglobulinemia
ANA
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ANA’s are directed against a variety of
nuclear antigens in serum of patients
with/without rheumatic disease as well as in
normal persons
The ANA IS NOT a useful screen for
rheumatic disease (nor is the RF)
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not sensitive enough (SNOUT)
not specific enough (SPIN)
The ANA IS a useful screen for SLE
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is very sensitive-95% (SNOUT)
Offers less in area of specificity (SPIN)
ANA
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many false positives
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5% of healthy controls pos at 1:160 dilution
10-15% of healthy controls pos at 1:80 dilution
30% of healthy controls pos at 1:40 dilution
positive with SBE / age / liver disease / thyroid dz
should be done on HEp2 cell line
pattern is important and helps w/ dx
titer doesn’t correlate with disease activity
a negative ANA “rules out” SLE most of the
time
ANA TESTING
Pre-test
ANA
Assessment
Low
< 1:80
likelihood
> 1:160
Moderate
< 1:80
likelihood
> 1:160
Your Action
High
likelihood
Fill out consult to
Rheum
Disease specific
antibodies
negative
positive
Ignore
Observe; look
elsewhere
Observe; look
elsewhere
Disease specific
antibodies
ANA PATTERNS
RIM
SPECKLED
HOMOGENEOUS
NUCLEOLAR
ANA PATTERNS
NUCLEOLAR
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Against RNA
Nonspecific
Associated with
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PSS
PM-DM
SLE
vasculitis
RIM or PERIPHERAL
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Against DNA
Specific for SLE
Should trigger check
for ds-DNA
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SLE
More active disease
Nephritis
ANA PATTERNS
CENTROMERE
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Associated with
CREST
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Calcinosis
Raynaud’s
Esophageal
Dysmotility
Sclerodactyly
Telangeictases
ANA PATTERNS
HOMOGENEOUS
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Against DNA &
histone
Nonspecific
Associated with
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SLE
Drug induced lupus
RA
Vasculitis
PM-DM
SPECKLED
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Against the various
ENA’s
“More” specific-SPIN
Associated with
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SLE
Sjogren’s
PSS
PM-DM
RA
SPECIFIC ANA’s
ds-DNA
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Nearly 100% specific
for SLE
Correlates well with
disease activity
Probably pathogenic
Moderate Sensitivity
SPECIFIC ANA’s
Smith (Sm)
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RNA/protein complex involved in processing
messenger RNA
More severe disease
Speckled ANA
Higher prevalence in AA & Asians
Moderate sensitivity (30%)
Highly specific for SLE
SPECIFIC ANA’s
RNP (U1 RNP)
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Ribonucleoprotein
Speckled ANA
Diagnostic of
MCTD if:
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High titer
No other ENA’s
Features of SLE, PM,
RA, and PSS
RF (+)
HISTONE
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High sensitivity and
low specificity
Drug induced lupus
gives anti-histone
alone
SLE gives antihistone along with
ds-DNA
Also seen in RA
SPECIFIC ANA’s
Ro/SS-A
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Protein-RNA complex
found in both nucleus
and cytoplasm
Sjogren’s and lupus
The rare ANA-neg lupus
Subacute cutaneous
lupus (a very
photosensitive lupus)
Neonatal SLE and
congenital heart block
La/SS-B
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Protein-RNA complex
found in both nucleus
and cytoplasm
Sjogren’s and lupus
The rare ANA-neg lupus
May protect against renal
disease
Usually also have
antibodies to
Ro/SS-A
Ro/SS-A & La/SS-B
SPECIFIC ANA’s
SCL-70
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Anti-topoisomerase I
Found in 20% of
patients with PSS
VERY specific
NOT sensitive
Lung disease
Associated with
nucleolar ANA
pattern
Jo-1
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Anti-histidyl tRNA
synthetase
A cytoplasmic protein
Found in 30% of
PM/DM patients –
often with lung
involvement/ILD
Highly specific
CRYOGLOBULINS
CRYOGLOBULINS
A group of serum Ig’s
with conformational
change in the cold:
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Precipitate or gel on
cold exposure
Phenomenon reversible
with rewarming
Found in variety of
clinical situations
Other labs: RF, low
complement, QIG, ESR
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TYPE I
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TYPE II (essential)
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Single monoclonal Ig or
light chain
“mixed” – a monoclonal
directed against
polyclonal IgG
(rheumatoid factor
activity)
TYPE III
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“polyclonal” – no
monoclonal Ig
also RF activity
CRYOGLOBULINS
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Type I (myeloproliferative disorders)
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Type II
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Myeloma, lymphoma, Waldenstrom’s
Infections (majority HCV and some HBV),
CTD (Sjogren’s, lupus),
Type III
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CTD, Infection
lymphoproliferative disorder
CRYOGLOBULINS
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“Essential mixed cryoglobulinemia” is now
recognized as driven by chronic Hep C in
most cases.
Clinical features:
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Acrocyanosis / digital necrosis (type I)
Palpable purpura (type II and III)
Livedo reticularis
Raynaud’s
Arthritis / GN / peripheral neuropathies
HLA B-27
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Class I MHC cell surface marker
found in 6-8% of NA whites, 3-4% of NA
AA’s, 18-50% of Haida Indians
90-100% of AS pts/lesser frequency in other
spondyloarthropathies
NOT a “screening” test for the SNSA’s
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IBD-associated arthritis – 50%
Ankylosing spondylitis (AS) – 90%
Reactive / Reiter’s – 80%
Psoriatic arthritis – 50% w/ spine; 15% peripheral
HLA B-27
ANTIPHOSPHOLIPID AB’s
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lupus anticoagulant
1.
2.
3.
4.
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anticardiolipin antibodies
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prolonged PTT or PT or final common pathway
(DRVVT)
Failure to correct by mixing patient plasma w/ nml
plasma
Correction with addition of excess phospholipid or
platelets
Ruling out other coagulopathies
via ELISA
antibodies against beta-2 glycoprotein
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Via ELISA
NEJM
7 Mar 2002
ANCA
C-ANCA and P-ANCA
Originally defined by
indirect IF staining
of neutrophils
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C-ANCA
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Cytoplasmic IF
pattern
P-ANCA
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Perinuclear IF pattern
ANCA (“C3PO”)
C-ANCA
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Ab against PR3
(proteinase-3) (found in
neuts/monos)
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Wegener’s
granulomatosis
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C-ANCA usually found in
widespread WG
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C-ANCA seen less frequently
with limited WG
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Correlates with dz
activity in 60% of cases
P-ANCA
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Ab against MPO
(myeloperoxidase),
elastase, lactoferrin, others
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Churg-Strauss
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MPAN
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Crescentic GN (pauciimmune GN)
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Drug-induced (PTU,
minocycline, hydralizine)
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IBD
 SLE / RA/HIV
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No correlation with
disease activity
ARTHROCENTESIS
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NORMAL/NONINFLAMMATORY (0-2,000
WBC)
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INFLAMMATORY (2,000-60,000 WBC)
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Transparent / < 25% POLYS
osteoarthritis / AVN / sympathetic effusion
Translucent / > 50% POLYS
RA / SLE / crystal / spondyloarthropathies
PURULENT (80,000-100,000 WBC)
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Infection / predominantly POLYS
SUMMARY
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No lab test is as good as your history and
physical exam
No lab test “screens” for CTD’s
Disease pattern recognition is far more
helpful than any serology or test
Know the SENS and SPEC of lab tests for
different diseases
Say “NO” to laboratory panels
QUESTIONS!!!