Rheumatology - Clinical Utility Of Serology And Lab Tests

Front 1

Bayes' Theorem

Back 1

Clinical utility of a test is highest when the pre-test probability is intermediate

Front 2

Lab tests available to help with rheumatology diagnosis

Back 2

Antinuclear antibody
Specific ANA's (dsDNA, ENA)
Complement
RF and anti-CCP
Anti neutrophil cytoplasmic Ab (ANCA)
Anti-phospholipid antiboides (APLA)
Uric acid
Creatinine and urinalysis
Synovial fluid analysis
Basic lab and acute phase reactants (CRP, ESR)

Front 3

SLE serology (with sensitivity and specificity)

Back 3

ANA - sensitivity=98%, specificity=poor
Anti dsDNA Ab - sensitivity=20-70%, specificity=98%
ENA: Ro, La, Sm (sensitivity=30-40%, specificity=100%)
Serum complements
APLA

Front 4

SLE serology technique

Back 4

ANA for screening (very sensitive)
If positive do dsDNA (specific), ENA and serum complement.
If ENA screen positive do panel and check Sm (specific).

Front 5

SLE serology: clinical utility of ANA, dsDNA, ENA and complements

Back 5

ANA: initial screen, no correlation with disease (do once only). If negative=no SLE
Sm: diagnosis
dsDNA: diagnosis + disease monitoring (if concordant)
Complements: disease monitoring (if concordant)

Front 6

Conditions with decreased serum complement

Back 6

Circulating immune complexes (SLE, cryoglobulinemia, hepatitis C, SBE, post strep glomerulonephritis)
Complement deficiency
Liver failure

Front 7

RA: tests for diagnosis

Back 7

ESR
RF
Xray

Front 8

RA: Sensitivity and specificity of RF

Back 8

Sensitivity: 60-80%
Specificity: 80-90%

Front 9

Conditions with elevated RF

Back 9

RA, Sjogren's syndrome, SLE, Sarcoidosis, Dermatomyositis/polymyositis, etc.

Front 10

RA: clinical utility of RF and anti-CCP

Back 10

RA: diagnosis (with other criteria), correlates with extra-articular features and disease severity, does not fluctuate with disease activity
Anti-CCP: diagnosis, poor correlation with extra articular features, not useful for disease monitoring
RF + anti-CCP - correlates with radiographic changes

Front 11

Specificity and Sensitivity of anti-CCP

Back 11

Sensitivity: 68%
Specificity: 95%

Front 12

Advantages and disadvantages of CRP

Back 12

Advantages: unaffected by age/gender, rapid response to inflammatory stimulation, wide range of clinically relevant values, can be measured and stored in sera, precise and reproducible
Disadvantages: expensive

Front 13

Advantages and disadvantages of ESR

Back 13

Advantages: reflects overall health status, provides good clinical information, relatively cheap
Disadvantages: Affected by age/gender/RBC, etc., reflects many plasma proteins, responds slowly, requires fresh sample

Front 14

Clinical utility of CRP and ESR

Back 14

No value for diagnosis
May help follow disease activity

Front 15

Clinical utility of creatinine and urinalysis

Back 15

"physical exam" of the kidney
Helps with diagnosis of many rheumatic conditions
Need biopsy for definitive diagnosis
Assess renal stability vs. progression

Front 16

Factors that decrease hemoglobin

Back 16

Anemia of chronic inflammatory disease
Red blood cell destruction by antibodies (SLE)
Drug effects

Front 17

Diseases that increase or decrease WBC

Back 17

Increase: Systemic vasculitis, infection
Decrease: SLE, drug effects

Front 18

Diseases that increase or decrease plateletts

Back 18

Increase: RA
Decrease: SLE, antiphospholipid syndrome, drug effects