The use of watermarking in the protection of medical relational databases requires that the introduced distortion does not hinder records interpretation. In this paper, we present the preliminary results of a watermarked data quality evaluation protocol developed so as to analyze the perception the practitioner has of the watermark. These results show that some attributes are more appropriate for watermarking than others and also that incoherent or unlikely records resulting from careless watermarking are easily identified by an expert.