Wednesday, 20 Nov 2019

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Hydroxychloroquine Blood Levels May Predict Future Retinopathy

A study of 527 patients receiving daily hydroxychloroquine (HCQ) concluded that hydroxychloroquine blood levels may predict future HCQ retinopathy.

This study assessed whether lower HCQ dosing, as recommended by the 2016 American Academy of Ophthalmology (AAO) guidelines (less than 5 mg/kg), would favorably affect retinopathy outcomes.

The overall risk of retinopathy was 4.3%, but was rare (1%) in the first 5 years, and rose with time - to 1.8% from 6 to 10 years, 3.3% from 11 to 15 years, 11.5% from 16 to 20 years, and 8.0% after 21 years of use.

Higher hydroxychloroquine blood levels were also predictive of hydroxychloroquine retinopathy (p=0.0124 and p=0.0340 for mean and maximum HCQ blood levels respectively).

Therefore, hydroxychloroquine blood levels may not only predict patient compliance but also a risk of future retinopathy. 

(Editor’s note: I personally have never monitored HCQ levels in my lupus or rheumatoid patients, but may be compelled to in patients who are not responsive or doing poorly and for the sole purpose of assessing HCQ adherence - not for future risk of retinopathy.)

Disclosures: 
The author has no conflicts of interest to disclose related to this subject

Rheumatologists' Comments

Jack: I am a huge believer in checking HCQ levels in all our SLE pts. I started doing so in all pts not in remission and was quite shocked to find that around 35-40% of my patients who weren't in remission were poorly compliant ( a few "favorites" even had zero for levels after promising me to my face that they were taking it.) Confronting pts greatly improved adherence rates and subsequently better disease control in my clinic. I also started checking levels in pts in remission after seeing Michelle Petri's initial abstract that preceded the complete study here and use it now to lower doses if >1500 and in remission. Think of all the pts over time who have had an immunosuppressant added or steroids increased when all it would have taken was reeducation about HCQ after discovering HCQ poor adherence on blood levels. The most common answer from poorly adherent patients was, "I did not think it was that important nor effective, I never really felt that much better on it." I do feel HCQ blood levels should be the standard of care in managing SLE patients. (Disclosure: I speak for Exagen ... I do so because I am such a big believer in the test)
Is the test available at the typical lab? What is the cost?

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