Is high titre ANA specific for connective tissue disease?

Objective A positive antinuclear antibody (ANA), while sensitive, is not specific for systemic lupus erythematosus or connective tissue diseases (CTD). The purp ose of the present study was to review those sera with a high titre (greate r than or equal to 4 dilutions above screening) ANA and determine from a re view of the charts if these higher titres offered a satisfactory specificit y for CTD. Methods All FANA testing in this region is carried out in one of two related labora tories. We reviewed the medical records of patients who had a positive ANA at a titre 4 dilutions above screenmg at this city-wide laboratory over a 6 -month period to determine whether this titre ("high titre") may offer rela tive diagnostic certainty. Antibody to extractable nuclear antigens (ENA) a nd native DNA were also obtained. Results 422 ANA results were positive at high titre. The medical record was availab le for review in 320 patients, of whom 238 (75%) were seen by a specialist physician, almost always including a rheumatologist. Our review determined that 35% had a diagnosis of connective tissue disease, 21% had a diagnosis of a possible/probable inflammatory disease, 16% had an alternative specifi c diagnosis provided, and in 29% no final disease specific diagnosis was re corded but CTD was not suggested to us or the specialist by the data availa ble. One or more anti-ENA antibodies and/or anti-DNA were positive in 69 (2 2%) and 8% of the sera tested respectively. Conclusion While long term follow-up is still required, a significant proportion of pa tients with high titre ANA have no CTD at the time of testing. Setting a hi gher cutoff for reporting of ANA may not increase specificity sufficiently to make it a useful alternative or addition to reporting a positive or nega tive value at screening titre alone.