Accurate diagnostic tests play an essential role in healthcare management. They help identify health conditions, estimate their stage, and determine genetic predisposition to develop the disease in the future, allowing for rapid and adequate medical treatment. While many of the various molecular diagnostic tests available today are utilized effectively, an increasing amount is reported to be lacking in value. Therefore, to avoid wasting resources and protect patients from unnecessary harm, the quality bar in the development of such tests should be set exceptionally high. Moreover, high-quality sample preparation is an essential step before the actual molecular analysis of the genetic material. This procedure includes stages such as sample isolation, purification, and concentration of the target product. As there are various reagents used in the process, which one should be the initial focus? The answer is Proteinase K of certified quality that assures high purity of tested nucleic acids.