CRD - Research - Laboratory

Detection of Antinuclear antibodies from Filter Paper Blood Clots
using Indirect Immunoenzyme technique.

ARVIND CHOPRA, AURADHA VENUGOPALAN, J EDMONDS
CENTER FOR RHEUMATIC DISEASES, PUNE DEPT. OF RHEUMATOLOGY, THE GEORGE HOSPITAL, AUSTRALIA

Aim

To evaluate indirect immunoenzyme (IIE) technique, for detection of antinuclear antibodies (ANA) using serum and filter paper blood clots (FPBC) especially for screening.

Methods

Antinuclear antibody processing from FPBC (prepared by expressing blood drops by finger pricking) was standardized in a pilot study. Paired samples (serum and corresponding FPBC) from 224 individuals [142 patients of systemic rheumatic diseases, chiefly lupus and rheumatoid arthritis (RA) and 82 healthy controls (HC)] were tested by the standard immunofluorescence (IIF) and IIE (using light microscope); samples were coded, blinded and randomly processed as per the protocol. End-point titers were determined for positive serum samples only. Standard reagents (Immunoconcepts Incorporation, USA) and controls (CDC, Atlanta, USA) were used. All patients were identified in a rheumatology referral practice in an Indian metropolis.

Results

	The sensitivity of IIE and IIF for SLE, using serum and FPBC was ~90%.
	The specificity of IIE and IIF for SLE, using serum and FPBC was in the range 66 – 73% and 58 – 63 % respectively.
	Good- perfect agreement (k>0.8) between the results obtained by IIE & IIF for all groups except RA;
	Except RA group, all other paired samples showed good concordance (72%) on testing for ANA patterns by both techniques.

Conclusions

IIE is a robust technique and should be considered a viable option to IIF at least in countries like India. And its further use on FPBC is a socioeconomically appealing proposition for carrying out population studies on lupus and related uncommon connective tissue disorders.

Key Indexing Terms

Antinuclear Antibodies; Immunoenzyme Method, Filter Paper Blood Sample, Systemic Lupus Erythematosus, Sero-epidemiology.

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