Td. Jaskowski et al., COMPARISON OF 3 COMMERCIALLY AVAILABLE ENZYME IMMUNOASSAYS FOR THE SCREENING OF AUTOANTIBODIES TO EXTRACTABLE NUCLEAR ANTIGENS, Journal of clinical laboratory analysis, 9(3), 1995, pp. 166-172
The initial screening test used in the diagnosis of connective tissue
diseases is based on the detection of antinuclear antibodies (ANA) by
indirect immunofluorescence (IFA). When the ANA screen is positive, it
is often useful to determine the specificity of the autoantibody to a
series of extractable nuclear antigens (ENA), a procedure that has be
en classically performed by double immunodiffusion. Testing large numb
ers of clinical specimens for autoantibodies to ENA by double diffusio
n techniques can be time-consuming and expensive. ENA screening system
s that employ enzyme immunoassay (EIA) technology have recently become
commercially available. We compared three EIA ENA assays to classic O
uchterlony double diffusion techniques. Furthermore, the sensitivity o
f each antigen and methodology (including ANA immunofluorescence using
HEp-2 cells) was tested using ENA positive sera possessing single aut
oantibodies. Two of the three EIAs that detected immunoglobulin G type
autoantibodies to Smith (Sm), ribonucleoprotein (RNP), Sjogren's synd
rome-associated antigens Ro (SSA) and La (SSB), were provided by INOVA
and Sigma Diagnostics. A third EIA, which also included scleroderma-a
ssociated antigen 70 (SCL-70/DNA-topoisomerase 1) and histidyl-tRNA sy
nthetase (JO-1) in addition to the four previously stated antigens, wa
s provided by Clark Laboratories. This latter ENA screen detected IgG,
IgA, and IgM type autoantibodies. Included in the study were sera cov
ering a wide variety of anti-nuclear and other autoantibodies. Sensiti
vity was 100% for all EIA ENA screens when compared to Ouchterlony dou
ble diffusion and specificity exceeded 95% in each case. Sensitivity s
tudies showed Ouchterlony to be less sensitive than EIA when detecting
low levels of autoantibodies to ENA. After the detection of ANA antib
ody by IFA, EIAs utilizing combined antigens can be used to screen lar
ge numbers of clinical specimens for autoantibodies against SSA, SSB,
Sm, RNP/SCL-70, and Jo-1 prior to confirmation by Ouchterlony double d
iffusion. (C) 1995 Wiley-Liss, Inc.