Utilizing a presumptive duration of illness > 30 days for two control samples from patients with rheumatoid arthritis with positive or equivocal IgM immunoblot results by Criteria B (Table 12, footnote (f)), we evaluated the impact of recategorizing these samples as negative by Criteria B; recategorization would not have significantly altered assay specificity or statistical comparisons with CDC criteria. This evidence concerns the gene CD40LG and rheumatoid arthritis.