Fig. 4

Relation between serum and whole-blood level of hydroxychloroquine (HCQ) in SLE patients with whole-blood levels < 300 ng/mL. The green and violet lines represent the HCQ level cut-off for non-adherence in serum (106 ng/mL) and whole blood (200 ng/mL), respectively. The orange square represents 14 patients who had both serum and whole-blood HCQ levels below the lower limit of quantification (20 ng/mL). Red crosses represent severe non-adherent patients with whole-blood HCQ levels between 20 and 200 ng/mL. Blue crosses represent patients with whole-blood HCQ levels between 200 and 300 ng/mL