Bubble map visualizing items from articles included in the review. A total of 24 items representing the different fields of action of HCQ have been grouped into clusters, based on their relatedness. The distance between the two terms represents the relatedness of the terms. Generally, the smaller the distance between two terms, the stronger the relationship of the terms to each other. Two items are closer to each other if they co-occurred more frequently in the evaluated publications. The item size indicates the words’ appearance frequency (multiple appearances in a single manuscript count as one). As explained in the legend, the time colors indicate the research focus over the years.