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Original Research

Somatotype, the risk of hydroxychloroquine retinopathy, and safe daily dosing guidelines

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Pages 811-818 | Published online: 03 May 2018

Figures & data

Table 1 Patient demographics

Figure 1 Receiver operating characteristic curves for hydroxychloroquine retin-opathy predicted by dosing guidelines as a univariate analysis.

Note: The red curve is the RBW method, the blue curve is the IBW method, and the green curve is the lesser of IBW and RBW methods.
Abbreviations: IBW, ideal body weight; RBW, real body weight.
Figure 1 Receiver operating characteristic curves for hydroxychloroquine retin-opathy predicted by dosing guidelines as a univariate analysis.

Figure 2 Receiver operating characteristic curves for hydroxychloroquine retin-opathy predicted by dosing guidelines as a multivariate analysis.

Notes: Logistic regression models were fit including gender, age, cumulative dose, and BMI as common predictive variables. The red curve corresponds to the model adding guidelines based on RBW dosing, the blue curve corresponds to the model adding guidelines based on IBW dosing, and the green curve corresponds to the model adding guidelines based on the lesser of IBW and RBW dosing.
Abbreviations: BMI, body mass index; IBW, ideal body weight; RBW, real body weight.
Figure 2 Receiver operating characteristic curves for hydroxychloroquine retin-opathy predicted by dosing guidelines as a multivariate analysis.

Figure 3 Predicted risk of hydroxychloroquine retinopathy versus BMI from multivariate logistic models with a common base model including gender, age, cumulative dose, and BMI, and differing according to whether the model included dosing guidelines based on RBW (A), IBW (B), or the lesser of RBW and IBW (C).

Notes: Each point refers to a single patient. The black curve is a spline fit of predicted risk to the data points with λ (a smoothing parameter) =1,000.
Abbreviations: BMI, body mass index; IBW, ideal body weight; RBW, real body weight.
Figure 3 Predicted risk of hydroxychloroquine retinopathy versus BMI from multivariate logistic models with a common base model including gender, age, cumulative dose, and BMI, and differing according to whether the model included dosing guidelines based on RBW (A), IBW (B), or the lesser of RBW and IBW (C).

Figure 4 Predicted risk of hydroxychloroquine retinopathy versus BMI from multivariate logistic regression models as described in .

Notes: (A) The predicted risk for the subgroups of patients taking ≥6.5 mg/kg/d (black line) and <6.5 mg/kg/d (gray line) of ideal body weight, respectively. (B) The predicted risk for the subgroups of patients taking ≥5.0 mg/kg/d (black line) and <5.0 mg/kg/d (gray line) of real body weight, respectively. The black and gray curves are spline fits of predicted risk to the data points with λ (a smoothing parameter) =1,000. The data points are not shown.
Abbreviation: BMI, body mass index.
Figure 4 Predicted risk of hydroxychloroquine retinopathy versus BMI from multivariate logistic regression models as described in Figure 3.

Figure 5 Allocation of patients into zones of safer dosing by the IBW or RBW methods using the IBW algorithm published by Melles and Marmor.Citation6

Notes: Each point refers to a patient. For patients who fall on the line, both methods yield the same recommended maximal safe dose. For patients who fall above the line, the RBW method yields a safer dose. For patients who fall below the line, the IBW method yields a safer dose.
Abbreviations: IBW, ideal body weight; RBW, real body weight.
Figure 5 Allocation of patients into zones of safer dosing by the IBW or RBW methods using the IBW algorithm published by Melles and Marmor.Citation6

Figure 6 Graph of the average weight for a woman in the age decile 50–59 years in the USA over the time span 1960–2012 from the NHANES.

Notes: The average patient taking hydroxychloroquine falls into this gender and age decile. The average weight of such a person has increased 27.5 pounds (18.8%).
Abbreviation: NHANES, National Health and Nutrition Examination Survey.
Figure 6 Graph of the average weight for a woman in the age decile 50–59 years in the USA over the time span 1960–2012 from the NHANES.

Figure 7 Risk versus body habitus based on ideal body weight and real body weight.

Notes: The data show that for obese patients (those with BMI >30), the risk of retinopathy was lower with the ideal body weight method of daily dosing compared to the real body weight method. Data from Melles and Marmor.Citation6
Abbreviation: BMI, body mass index.
Figure 7 Risk versus body habitus based on ideal body weight and real body weight.