IMPACT OF USING STORED CELLS FOR IMMUNOFLUORESCENCE DETECTION OF ANTIPERINUCLEAR FACTOR ON SENSITIVITY OF THE METHOD FOR THE DIAGNOSIS OF RHEUMATOID-ARTHRITIS

Antiperinuclear factor is as sensitive as (0.75 to 0.80) and more spec ific than (0.94 to 0.97) rheumatoid factor for the diagnosis of rheuma toid arthritis. Although three groups found similar performance charac teristics using the assay technique described by Youinou, lower sensit ivities have also been reported. To clarify these discrepancies, we in vestigated each parameter of the assay, including storage time of the oral mucosa cells used as the substrate. Even when the slides were fro zen, titers fell by one dilution within the first week and by two dilu tions within two weeks after sampling. This decline seemed related to storage rather than to freezing: slides kept at 4 degrees C yielded an apparent three-dilution fall in titers after one week and were uneval uable after longer storage times. Successive freeze-thaw cycles did no t influence results when the assay was done on the day the cells were sampled and fixed. Titers in sera stored at -25 degrees C remained unc hanged or decreased by no more than one dilution during the first 18 m onths but declined thereafter. These data emphasize the need for perfo rming the assay on the same day or, at the latest, on the day after fi xation of the slides. That this precaution was taken should be specifi ed in the ''Methods'' section of articles on antiperinuclear factor de tection.