title: Very low blood hydroxychloroquine concentration as an objective marker of poor adherence to treatment of systemic lupus erythematosus.
abstract: BACKGROUND
  Poor adherence to treatment is difficult to diagnose accurately. Hydroxychloroquine (HCQ) has a long elimination half-life and its concentration in whole blood can be measured easily.
  
  
  OBJECTIVE
  To evaluate the utility of a very low blood HCQ concentration as a marker of poor compliance in patients with systemic lupus erythematosus (SLE).
  
  
  METHODS
  HCQ concentrations were determined on a blinded basis in 203 unselected patients with SLE. At the end of the study, the patients were informed of the results and retrospectively interviewed about their adherence to treatment.
  
  
  RESULTS
  14 (7%) patients said that they had stopped taking HCQ (n = 8) or had taken it no more than once or twice a week (n = 6). Their mean (SD) HCQ concentration was 26 (46) ng/ml. range (0-129 ng/ml) By contrast, the other patients had a mean HCQ concentration of 1079 ng/ml range (205-2629 ng/ml). The principal barriers to adherence were related to HCQ treatment characteristics. Adherence subsequently improved in 10 of the 12 patients whose blood HCQ concentrations were remeasured.
  
  
  CONCLUSIONS
  Very low whole-blood HCQ concentrations are an objective marker of prolonged poor compliance in patients with SLE. Regular drug assays might help doctors in detect non-compliance and serve as a basis for counselling and supporting these patients.
authors.affiliation: AP-HP, Service de Médecine Interne, Centre de Référence National pour le Lupus Systémique et le Syndrome des Antiphospholipides, CHU Pitié-Salpêtrière, 47-83 Boulevard de l'Hôpital, 75651 Paris Cedex 13, France. nathalie.costedoat@psl.aphp.fr
authors.forename: Nathalie
authors.initials: N
authors.lastname: Costedoat-Chalumeau
authors.forename: Zahir
authors.initials: Z
authors.lastname: Amoura
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Hulot
authors.forename: Guy
authors.initials: G
authors.lastname: Aymard
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Leroux
authors.forename: Donata
authors.initials: D
authors.lastname: Marra
authors.forename: Philippe
authors.initials: P
authors.lastname: Lechat
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Piette
mesh_terms: D000328:Adult; D018501:Antirheumatic Agents / Q000097:blood* / Q000627:therapeutic use; D001294:Attitude to Health; D015415:Biomarkers / Q000097:blood; D016903:Drug Monitoring / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006886:Hydroxychloroquine / Q000097:blood* / Q000627:therapeutic use; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance / Q000523:psychology; D010352:Patient Dropouts / Q000523:psychology; D012720:Severity of Illness Index
chemical_list: D018501:Antirheumatic Agents; D015415:Biomarkers; D006886:Hydroxychloroquine