SEOUL, SOUTH KOREA – Regular testing of hydroxychloroquine levels in patients with systemic lupus erythematosus – especially those who are experiencing a disease flare – could help to identify patients who are not taking their treatment and are at risk of worse outcomes.
Data presented at an international congress on systemic lupus erythematosus showed that 7.3% of patients with SLE are severely nonadherent to their medication and have a higher risk of flare, early damage, and mortality.
Rheumatologist Nathalie Costedoat-Chalumeau, MD, PhD, professor of internal medicine at Cochin Hospital, Paris, presented data from 660 patients enrolled in the international longitudinal SLICC Inception Cohort, who had all been on hydroxychloroquine therapy for at least 3 months at baseline.
Patients’ serum hydroxychloroquine levels were measured at baseline and follow-up, and severe nonadherence was defined as below 106 ng/mL for those on 400 mg/day or 53 ng/mL for those on 200 mg/day.
Dr. Costedoat-Chalumeau said that those thresholds were chosen based on earlier work that analyzed the blood concentration of hydroxychloroquine in a group of patients and identified a group with very low concentrations corresponding to severe nonadherence.
“Since then, it has been reproduced by others with the same threshold,” she said. “When you have very low levels of hydroxychloroquine in their blood, you know that your patients don’t take their treatment.”
In the present study, the 7.3% of patients who met the criteria for severe nonadherence had a significant 3.3-fold higher risk of disease flare within a year of enrollment than did those who were adherent. They also had significantly higher mortality at 5 years after enrollment.
While the study didn’t show a significant difference in the level of damage at 5 years – defined as a worsening of their SLICC damage index – Dr. Costedoat-Chalumeau said they saw significantly greater damage occurring at 1, 2, and 3 years after enrollment among those who were severely nonadherent.
The challenge with recognizing these nonadherent patients is that they have no obvious differences at baseline from those who are adherent, Dr. Costedoat-Chalumeau said. The rates of nonadherence were similar regardless of what dose the patient was on, their ethnicity, gender, education level, or other demographic variables.
“I believe strongly that there is a benefit of testing hydroxychloroquine levels in the blood or serum to detect severe nonadherence,” she said.
At Dr. Costedoat-Chalumeau’s clinic, patients’ hydroxychloroquine levels are tested at every clinic visit, she said in an interview, and especially if they are experiencing a disease flare. “We want to know if the flare is because the patient is not taking the treatment or if it’s because the treatment is not effective, which is very different in terms of management,” she said. She recommended waiting at least 1 month after patients start treatment before measuring their hydroxychloroquine levels.
As to why some patients choose to stop taking their medication, Dr. Costedoat-Chalumeau said sometimes it was because patients were worried about side effects, but others were also unclear about why they needed to keep taking hydroxychloroquine.
“They think steroids are effective because when they take it they are better, but they don’t see the effect of hydroxychloroquine,” she said. “You have to explain that it doesn’t work the same.”
Commenting on the findings, session chair Joan Merrill, MD, professor of medicine at the University of Oklahoma Health Sciences Center, Oklahoma City, said the data show that severe nonadherence does have prognostic significance. “Many patients with SLE have low-grade disease or inflammation in the blood vessels that may not be clinically apparent and which hydroxychloroquine can help, so it might be wise to routinely get blood levels,” she said.
Dr. Costedoat-Chalumeau reported no relevant financial relationships apart from unrestricted institutional research grants from UCB and Roche.