Advances in the Clinical Use of Hydroxychloroquine Levels

Katherine Chakrabarti; W. Joseph McCune


Curr Opin Rheumatol. 2022;34(3):151-157. 

In This Article

Measurement of Hydroxychloroquine Levels

Hydroxychloroquine levels are measured by liquid chromatography or tandem mass spectrometry in isolation or in combination.[2,3] Levels can be measured in whole blood, serum or plasma, although whole blood is the preferred sample.[4,5] In a study of 26 lupus patients, whole blood had a concentration twice as high as serum or plasma (mean level 813 vs. 436 ng/ml for serum and 362 ng/ml for plasma).[4] A strong correlation was noted between serum levels of hydroxychloroquine and whole blood levels (R2 = 0.82) but a poor correlation between plasma levels and whole blood levels (R2= 0.46) suggesting that plasma levels should be avoided[4] as documented in the figure from Carlsson et al., which also corroborates the lack of a correlation between hydroxychloroquine dose and level, further strengthening the role of measuring hydroxychloroquine levels (Figure 2). In this review, blood levels refer to whole blood levels as the default measure except when otherwise specified.

Figure 2.

A strong correlation exists between hydroxychloroquine serum and whole blood levels while the correlation between plasma and whole blood is weaker and plasma measurements were less reproducible. (a) Graph of HCQ serum vs. HCQ whole blood levels. (b) Graph of HCQ plasma vs. HCQ whole blood levels. Various doses of HCQ are indicated as follows: circle = 1400 mg/week, triangle = 2000 mg/week, diamond 2800 mg/week. Adapted with permission from Carlsson et al. [4]. HCQ, hydroxychloroquine.