Detection of antinuclear antibodies: added

value of solid phase assay? Agmon-Levin et al1 formulated recommendations for the assess-ment of antinuclear antibodies (ANA). Indirect immunofluores-cence (IIF) is considered the reference method for ANA screening, which is in agreement with the American College of Rheumatology (ACR) position statement.2 The recommenda-tions are based on current knowledge and expert experience. However, as recognised by Meroni and Schur,2 no well-planned studies comparing the diagnostic accuracy of the old IIF and the new methods have been undertaken. In a recent study, IIF was compared to a new automated method for connective disease screening (fluoroenzymeimmunoassay (FEIA) (EliA CTD screen, Thermo Fisher)) using samples obtained at the time of diagnosis from well-characterised patients and con-trols.3 Diagnostic accuracy data (for systemic lupus erythematosus (SLE), systemic sclerosis (SSc) and Sjögren’s syndrome (SS)) from this study is recapitulated in table 1. For comparison, data from a multinational study4 on IIF is included in the Table as well. The results for IIF in the two studies were comparable, thereby validat-ing the study population. A higher specificity was observed for FEIA than for IIF (especially at IIF cutoff dilution 1:80), whereas sensitivity was higher for IIF than for FEIA for SLE and SSc, but not for SS. The diagnostic performance of FEIA was comparable to the performance of a multiplexed bead assay.5 For the combination of IIF and FEIA, the highest likelihood ratios (LR) (35–50) were found for double positivity (FEIA and IIF), the lowest (0.03–0.11) for double negativity. IIF positivity combined with FEIA negativity (22–25 % of SLE and SSc patients) had a low LR (<5). Table 1 Likelihood ratios for systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and Sjögren’s syndrome (SS) for test results obtained by indirect immunofluorescence (IIF) (at two different cutoff dilutions),3 4 EliA CTD screen,3 and a combination of IIF and EliA CTD screen (calculated for this manuscript) Systemic lupus erythematosus Systemic sclerosi