<P> Enzyme - linked immunosorbent assay (ELISA) uses antigen - coated microtitre plates for the detection of ANAs . Each well of a microtitre plate is coated with either a single antigen or multiple antigens to detect specific antibodies or to screen for ANAs, respectively . The antigens are either from cell extracts or recombinant . Blood serum is incubated in the wells of the plate and is washed out . If antibodies that bind to antigen are present then they will remain after washing . A secondary anti-human antibody conjugated to an enzyme such as horseradish peroxidase . The enzyme reaction will produce a change in colour of the solution that is proportional to the amount of antibody bound to the antigen . There are significant differences in the detection of ANA by immunofluorescence and different ELISA kits and there is only a marginal agreement between these . A clinician must be familiar with the differences in order to evaluate the outcomes of the various assays . </P> <P> The following table lists the sensitivity of different types of ANAs for different diseases . </P> <Table> <Tr> <Th> ANA type </Th> <Th> Target antigen </Th> <Th_colspan="7"> Sensitivity (%) </Th> </Tr> <Tr> <Th> SLE </Th> <Th> Drug - induced LE </Th> <Th> Diffuse systemic sclerosis </Th> <Th> Limited systemic scleroderma </Th> <Th> Sjögren syndrome </Th> <Th> Inflammatory myopathy </Th> <Th> MCTD </Th> </Tr> <Tr> <Th> All ANAs (by indirect IF) </Th> <Td> Various </Td> <Td>> 95 </Td> <Td>> 95 </Td> <Td> 70--90 </Td> <Td> 70--90 </Td> <Td> 50--80 </Td> <Td> 40--60 </Td> <Td> 95 </Td> </Tr> <Tr> <Th> Anti-dsDNA </Th> <Td> DNA </Td> <Td> 40--60 </Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td> - </Td> </Tr> <Tr> <Th> Anti-Sm </Th> <Td> Core proteins of snRNPs </Td> <Td> 20--30 </Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td> - </Td> </Tr> <Tr> <Th> Anti-histone </Th> <Td> Histones </Td> <Td> 50--70 </Td> <Td> 90--95 </Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td> - </Td> </Tr> <Tr> <Th> Anti Scl - 70 </Th> <Td> Type I topoisomerase </Td> <Td>--</Td> <Td>--</Td> <Td> 28--70 </Td> <Td> 10--18 </Td> <Td>--</Td> <Td>--</Td> <Td> - </Td> </Tr> <Tr> <Th> Anti-centromere </Th> <Td> Centromeric proteins </Td> <Td>--</Td> <Td>--</Td> <Td> 22--26 </Td> <Td> 90 </Td> <Td>--</Td> <Td>--</Td> <Td> - </Td> </Tr> <Tr> <Th> Anti-snRNP70 </Th> <Td> snRNP70 </Td> <Td> 30 - 40 </Td> <Td> - </Td> <Td> 15 </Td> <Td> 10 </Td> <Td> - </Td> <Td> 15 </Td> <Td> 90 </Td> </Tr> <Tr> <Th> SS - A (Ro) </Th> <Td> RNPs </Td> <Td> 30--50 </Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td> 70--95 </Td> <Td> 10 </Td> <Td> - </Td> </Tr> <Tr> <Th> SS - B (La) </Th> <Td> RNPs </Td> <Td> 10--15 </Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td> 60--90 </Td> <Td>--</Td> <Td> - </Td> </Tr> <Tr> <Th> Jo - 1 </Th> <Td> Histidine - tRNA ligase </Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td>--</Td> <Td> 25 </Td> <Td> - </Td> </Tr> <Tr> <Td_colspan="9">--= less than 5% sensitivity <P> Unless else specified in boxes, then ref is: </P> </Td> </Tr> </Table> <Tr> <Th> ANA type </Th> <Th> Target antigen </Th> <Th_colspan="7"> Sensitivity (%) </Th> </Tr>

Hep-2 substrate antinuclear antibodies (ana) serum