OBJECTIVE: To compare quantitative nephelometry to the traditional semiquantitative latex agglutination (LAT) test for rheumatoid factor (RF). METHODS: We evaluated 564 patients with rheumatoid arthritis (RA) and 155 controls using both techniques. The cutoff value of 40 IU/ml was established for a positive RF result. RESULTS: Sensitivity of LAT and nephelometry was 85.5% and 88.3%, respectively. Both techniques had a similar specificity and a positive predictive value exceeding 95%. Agreement (kappa = 0.86) and correlation (0.87) between the 2 methods were significant. CONCLUSION: In routine practice, and particularly in developing countries such as India, LAT can still be the preferred method for RF determination.
OBJECTIVE: To compare quantitative nephelometry to the traditional semiquantitative latex agglutination (LAT) test for rheumatoid factor (RF). METHODS: We evaluated 564 patients with rheumatoid arthritis (RA) and 155 controls using both techniques. The cutoff value of 40 IU/ml was established for a positive RF result. RESULTS: Sensitivity of LAT and nephelometry was 85.5% and 88.3%, respectively. Both techniques had a similar specificity and a positive predictive value exceeding 95%. Agreement (kappa = 0.86) and correlation (0.87) between the 2 methods were significant. CONCLUSION: In routine practice, and particularly in developing countries such as India, LAT can still be the preferred method for RF determination.