The photometric latex test for rheumatoid factors in patients with rheumatoid arthritis. II. Clinical evaluation.

The photometric latex test (PLT) for the detection of rheumatoid factors has been clinically evaluated. PLT titers have been closely studied in relation to clinical and laboratory parameters by means of parametric and nonparametric statistical methods. An analysis of the sensitized sheep cell test (SSC) titers has also been undertaken. The subjects comprised 377 patients with rheumatoid arthritis (RA) and 120 controls. The medical data recorded included sex, age, diagnosis, anatomical stage, functional class, duration and course of the disease, presence of the American Rheumatism Association (ARA) criteria, blood sedimentation rate, red and white blood counts, haemoglobin concentration, total protein content, serum protein levels, and SSC and PLT titers. A multivariate stepwise regression analysis with eight normally distributed variables was made. In accordance with previous findings, a significant correlation was shown to exist between the serum protein levels and the development of the RA when the anatomical stage, functional class and course of the disease were used as parameters of disease activity. In the RA patients there was also correlation between the serologic titers and the serum protein levels, and the anatomical stage, functional class and course of the disease, and the sedimentation rate, thus showing that titers can also serve as a measure of the inflammatory process. There was a significant correlation between the number of ARA criteria and the titers in the RA patients but not in the controls. The course of the disease correlated with the serum titers and other inflammatory parameters, a finding showing that the course of the disease is an important diagnostic parameter with possible prognostic value. Correlation was also demonstrated between the white blood count and the titers. It is concluded that the sedimentation rate, albumin and gamma-globulin levels, and PLT titer are the best parameters of disease activity. The titer values are not only of diagnostic importance but have prognostic value as regards the severity of the disease.