Low serum levels of hydroxychloroquine (HCQ) among patients with systemic lupus erythematosus are associated with a threefold increased likelihood of physician- and patient-reported nonadherence to the medication. In addition, routine monitoring of HCQ levels are associated with improvements in adherence and disease activity.
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Those are two key findings from a systematic review and meta-analysis published in Arthritis Care & Research.
“HCQ is recommended for all patients with systemic lupus erythematosus (SLE, or lupus) to reduce disease activity and improve damage-free-survival,” the authors, led by Shivani Garg, MD, of the University of Wisconsin–Madison, wrote in the article. “Yet, up to 83% of lupus patients are nonadherent to HCQ commonly because of poor understanding of benefits of HCQ, lack of motivation to continue therapy, and inflated concerns regarding side effects from HCQ use.”
For their analysis, the researchers drew from 17 published observational and interventional studies that measured HCQ levels and assessed adherence or Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) in adults with SLE. They used forest plots to compare pooled estimates of correlations between HCQ levels and reported nonadherence, or SLEDAI scores. Patient-reported nonadherence was defined as less than 80% medication adherence reported, and physician-reported adherence was estimated based on physicians’ interpretations of the previous month’s adherence as reported by patients during clinic visits.
The study population consisted of 1,223 patients. Dr. Garg and colleagues found a threefold higher odds of reported nonadherence in patients with low HCQ levels (odds ratio, 2.95; P less than .001). The mean SLEDAI score was 3.14 points higher in a group with below-threshold HCQ levels on a priori analysis (P = .053), and 1.4 points higher in a group with HCQ levels below 500 ng/mL (P = .039). Among all patients, those with HCQ levels 750 ng/mL or greater had a 58% lower risk of active disease, and their SLEDAI score was 3.2 points lower. “Our study support levels greater than or equal to 750 ng/mL to be clinically meaningful and statistically significant to identify disease flare (change in SLEDAI greater than or equal to 3 points) and predict active disease (SLEDAI greater than or equal to 6),” the authors wrote.
Dr. Michelle Petri
In an interview, Michelle A. Petri, MD, MPH, took issue with the HCQ goal of 750 ng/mL or greater recommended by the authors. “I think that was premature,” said Dr. Petri, professor of medicine at Johns Hopkins University, Baltimore. “We presented data at last year’s ACR [which showed] that the level needs to be higher than that to prevent thrombosis. But it is important to open the discussion that HCQ blood levels are not just for nonadherence. I believe they will help us to reduce retinopathy, and also to make sure the dose remains in an efficacious range, such as what is needed to prevent thrombosis.”
Dr. Petri, who also directs the Hopkins Lupus Center, said that the study’s overall conclusions confirms the need for blood testing for HCQ to identify nonadherence. “Everyone remembers the saying of the [former] Surgeon General Dr. C. Everett Koop: ‘Drugs can’t work if patients don’t take them!’ – in particular, blood levels which represent what the patient has taken in the last month. I call blood levels the ‘lupus A1C.’ ”
She added that HCQ blood levels have utility for nonadherence, prediction of retinopathy, and prevention of thrombosis. Such tests “are now much more widely available, including by some large national laboratories such as Quest Diagnostics, as well as by Exagen. No more excuses.” LabCorp plans to start offering HCQ blood level testing by the middle of 2020, she said.
In their manuscript, the study authors acknowledged certain limitations of their analysis, including the fact that there were only four studies that measured HCQ levels and nonadherence or SLEDAI. “Second, most of the studies that examined the correlation between reported adherence and HCQ blood levels were performed in Europe, and there was only one small U.S. study,” they wrote. “Therefore, generalizability for our findings could be limited because of differences in cultural beliefs, social issues, and insurance/medical coverage in populations from diverse countries.”
The study authors reported having no disclosures. Dr. Petri disclosed that she has conducted research on HCQ that was funded by the National Institutes of Health. She has also conducted research for Exagen.
SOURCE: Garg S et al. Arthritis Care Res. 2020 Jan 31. doi: 10.1002/acr.24155.