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Laboratory Evaluation of Connective Tissue Disease

Dr. Ajay Wanchu, M.D., D.M

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C Reactive Protein (CRP)

It is one of the acute phase proteins whose value is raised in inflammatory arthritic condition such as RA, JCA and patients with seronegative spondyloarthopathy (SSA). Interestingly, in SLE though the ESR rises the CRP is normal in active disease but in presence of infection it CRP rises. This is measured by latex agglutination and also by turbidimetry and, therefore, more expensive than ESR.

HLA (Human Leukocyte Antigen)

Despite the strong association of HLA B27 with SSA group of disease, this does not have diagnostic significance. Therefore, in conclusion I have attempted to describe briefly about the various investigations that are currently being used for management of patients with connective tissue disease. They are very useful in making a diagnosis and following up a patient provided the limitations are kept in mind.

Table I: Prevalence of ANA positivity in various disorders

Disease Incidence of ANA positivity (%)
Systemic lupus erythematosus 99
Drug induced lupus 100
Systemic sclerosis 97
Mixed connective tissue disease 93
Inflammatory myositis 78
Sjogren’s syndrome 96

Table II: Spectrum of antibodies associated with Systemic lupus erythematosus

Antibody specificity Prevalence (%)
dsDNA 70
Histone 60
Chromatin 85
Sm 25
U1RNP 35
Ro (SSA) 40
La (SSB) 15

Table III: Staining Patterns of antinuclear antibodies on Indirect Immunoflourescence

Type Antibodies against Disease association(s)
Diffuse/Homogenous Native DNA Histones SLE, Drug induced SLE, RA
Speckled Extractable nuclear antigens like Sm and RNP; Centromere Mixed connective tissue disease, SLE, SS, SSc
Nucleolar RNA polymerase I, PM-Scl SSc, SS, SLE, Inflammatory myositis
Rim dsDNA, possibly histones SLE

Table IV: Diversity of anti-ENA antibodies and their clinical relevance

Antibodies against Disease Association(s) Remark(s)
Sm SLE Highly specific
U1RNP Mixed connective tissue disease Also seen in SLE, Myositis, SS
Ro (SSA) SLE, Primary SS, RA Neonatal lupus, Subacute cutaneous lupus
La (SSB) Primary SS, SLE Often seen with Ro
Topoisomerase -1 SSc – diffuse cutaneous type Earlier called Scl-70
Jo-1 Poly/Deramtomyositis One of the myositis specific antibodies
PM/Scl Poly/Deramtomyositis, SSc Seen with overlapping features of both
Nucleolar Poly/Deramtomyositis, SSc Seen with overlapping features of both

Dr. Ajay Wanchu, M.D., D.M
Department of Internal Medicine, PGIMER, Chandigarh

Department of Internal Medicine, PGIMER, Chandigarh

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