Arthritis Research & Therapy (Sep 2020)

Hydroxychloroquine levels in patients with systemic lupus erythematosus: whole blood is preferable but serum levels also detect non-adherence

  • Benoit Blanchet,
  • Moez Jallouli,
  • Marie Allard,
  • Pascale Ghillani-Dalbin,
  • Lionel Galicier,
  • Olivier Aumaître,
  • François Chasset,
  • Véronique Le Guern,
  • Frédéric Lioté,
  • Amar Smail,
  • Nicolas Limal,
  • Laurent Perard,
  • Hélène Desmurs-Clavel,
  • Du Le Thi Huong,
  • Bouchra Asli,
  • Jean-Emmanuel Kahn,
  • Laurent Sailler,
  • Félix Ackermann,
  • Thomas Papo,
  • Karim Sacré,
  • Olivier Fain,
  • Jérôme Stirnemann,
  • Patrice Cacoub,
  • Gaelle Leroux,
  • Judith Cohen-Bittan,
  • Jérémie Sellam,
  • Xavier Mariette,
  • Claire Goulvestre,
  • Jean Sébastien Hulot,
  • Zahir Amoura,
  • Michel Vidal,
  • Jean-Charles Piette,
  • on behalf of the PLUS Group,
  • Noémie Jourde-Chiche,
  • Nathalie Costedoat-Chalumeau

DOI
https://doi.org/10.1186/s13075-020-02291-z
Journal volume & issue
Vol. 22, no. 1
pp. 1 – 10

Abstract

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Abstract Background Hydroxychloroquine (HCQ) levels can be measured in both serum and whole blood. No cut-off point for non-adherence has been established in serum nor have these methods ever been compared. The aims of this study were to compare these two approaches and determine if serum HCQ cut-off points can be established to identify non-adherent patients. Methods HCQ levels were measured in serum and whole blood from 573 patients with systemic lupus erythematosus (SLE). The risk factors for active SLE (SLEDAI score > 4) were identified by multiple logistic regression. Serum HCQ levels were measured in 68 additional patients known to be non-adherent, i.e. with whole-blood HCQ < 200 ng/mL. Results The mean (± SD) HCQ levels were 469 ± 223 ng/mL in serum and 916 ± 449 ng/mL in whole blood. The mean ratio of serum/whole-blood HCQ levels was 0.53 ± 0.15. In the multivariate analysis, low whole-blood HCQ levels (P = 0.023), but not serum HCQ levels, were independently associated with active SLE. From the mean serum/whole-blood level ratio, a serum HCQ level of 106 ng/mL was extrapolated as the corresponding cut-off to identify non-adherent patients with a sensitivity of 0.87 (95% CI 0.76–0.94) and specificity of 0.89 (95% CI 0.72–0.98). All serum HCQ levels of patients with whole-blood HCQ below the detectable level (< 20 ng/mL) were also undetectable (< 20 ng/mL). Conclusions These data suggest that whole blood is better than serum for assessing the pharmacokinetic/pharmacodynamic relation of HCQ. Our results support the use of serum HCQ levels to assess non-adherence when whole blood is unavailable.

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