Figure 4.
 Association between RBC folate PG concentrations and the number of tender and swollen joints. (A) Higher daily folic acid doses resulted in higher RBC folate PGs (p = 0.009). (B) In a univariate linear regression, higher folate PGs were associated with a higher number of tender (p = 0.002) and swollen joints (p = 0.006). The number of tender and swollen joints calculated from the univariate regression is given for folate PGs in the 10th (622 nmol/l), 25th (738 nmol/l), 50th (1062 nmol/l), 75th (1447 nmol/l), and 90th centile (1736 nmol/l) of the patient population. Bars represent values with 95% CI.