Standardisation of serological tests for rheumatoid factor measurement

Standardisation of quantitative data obtained by several types of rheumatoid factor test was achieved by the use of a reference serum preparation. Interlaboratory comparability improved for the latex fixation test, the Waaler-Rose test, the IgM RF test by an enzyme linked immunosorbent assay (ELISA), and for the antiperinuclear factor test. Use of a common method and latex preparation was not sufficient to improve comparability for the latex test. The comparability of IgM RF tests by immunofluorescence (IF) was not changed by reading against a common reference. It is concluded that expression in international units, as defined by the World Health Organisation (WHO), improves interlaboratory comparison of quantitative data in rheumatoid serology.