Low blood concentration of hydroxychloroquine is a marker for and predictor of disease exacerbations in patients with systemic lupus erythematosus.
OBJECTIVE
To study the possible relationship between whole-blood hydroxychloroquine (HCQ) concentrations and clinical efficacy of HCQ in patients with systemic lupus erythematosus (SLE).


METHODS
Whole-blood HCQ concentrations were measured, under blinded conditions, in 143 unselected patients with SLE who had been receiving HCQ 400 mg daily for at least 6 months. The relationship of these concentrations to current disease activity and to subsequent exacerbations during 6 months of followup was investigated.


RESULTS
At baseline, 23 patients had active disease (mean +/- SD SLE Disease Activity Index 12.4 +/- 7.5). The mean whole-blood HCQ concentration in this group was significantly lower than that in the 120 patients with inactive disease (694 +/- 448 ng/ml versus 1,079 +/- 526 ng/ml; P = 0.001). Among the 120 patients who had inactive disease at baseline, the mean HCQ concentration at baseline in the 14 (12%) who had disease exacerbations during followup was significantly lower than that in the patients whose disease remained inactive. Multivariate logistic regression showed that the HCQ concentration was the only predictor of exacerbation (odds ratio 0.4 [95% confidence interval 0.18-0.85], P = 0.01). Receiver operating characteristic curve analysis showed that a whole-blood HCQ concentration cutoff of 1,000 ng/ml had a negative predictive value of 96% for exacerbation during followup.


CONCLUSIONS
Low whole-blood HCQ concentrations are associated with SLE disease activity and are a strong predictor of disease exacerbation. Regular drug assaying and individual tailoring of treatment might help to improve the efficacy of HCQ treatment in patients with SLE.
Costedoat-Chalumeau
Nathalie
N
Assistance Publique-Hôpitaux de Paris, Centre Hospitalier Universitaire Pitié-Salpêtrière, Université Paris VI Pierre et Marie Curie, Paris, France. nathalie.costedoat@psl.aphp.fr
Amoura
Zahir
Z
Hulot
Jean-Sébastien
JS
Hammoud
Hala Abou
HA
Aymard
Guy
G
Cacoub
Patrice
P
Francès
Camille
C
Wechsler
Bertrand
B
Huong
Du Le Thi
du LT
Ghillani
Pascale
P
Musset
Lucile
L
Lechat
Philippe
P
Piette
Jean-Charles
JC
D000328:Adult; D015415:Biomarkers / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D018450:Disease Progression; D005260:Female; D006801:Humans; D006886:Hydroxychloroquine / Q000097:blood* / Q000627:therapeutic use; D016015:Logistic Models; D008137:Longitudinal Studies; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012720:Severity of Illness Index
D015415:Biomarkers; D006886:Hydroxychloroquine