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Very low blood hydroxychloroquine concentration as an objective marker of poor adherence to treatment of systemic lupus erythematosus.
  1. Nathalie Costedoat-Chalumeau (nathalie.costedoat{at}
  1. pitié-salpêtrière, France
    1. Zahir Amoura
    1. pitié-salpêtrière, France
      1. Jean-Sébastien Hulot
      1. Université Pierre et Marie Curie, France
        1. Guy Aymard
        1. Université Pierre et Marie Curie, France
          1. Gaëlle Leroux
          1. pitié-salpêtrière, France
            1. Donata Marra
            1. pitié-salpêtrière, France
              1. Philippe Lechat
              1. Université Pierre et Marie Curie, France
                1. Jean-Charles Piette
                1. Université Pierre et Marie Curie, France


                  Objective: Poor adherence to treatment is very difficult to diagnose accurately. Hydroxychloroquine (HCQ) has a long elimination half-life and its concentration in whole blood can be measured easily. We evaluated the utility of a very low blood HCQ concentration as a marker of poor compliance in patients with systemic lupus erythematosus (SLE).

                  Methods: We determined HCQ concentrations on a blinded basis in 203 unselected SLE patients. At the end of the study, patients were informed of the results and retrospectively interviewed about their adherence to treatment.

                  Results: 14 patients (7%) said they had stopped taking HCQ (n=8) or had taken it no more than once or twice a week (n=6). Their mean HCQ concentration was 26 ± 46 ng/mL [0-129]. In contrast, the other patients had a mean HCQ concentration of 1079 ng/mL [205-2629]. 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 SLE patients. Regular drug assays might help physicians to detect noncompliance and serve as a basis for counseling and supporting these patients.

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