What must be ensured when allowing blood to dry on NMS collection paper?

The correct choice emphasizes the importance of uniformity when allowing blood to dry on NMS collection paper. Ensuring that all blood drops soak through evenly is critical for accurate laboratory analysis. If blood does not soak evenly, it can lead to unreliable results during subsequent testing, as variations in thickness and saturation can affect the integrity of the sample. An even application helps to achieve consistent results and ensures that the analytes of interest are adequately represented and preserved on the collection paper.

Other aspects, like the requirement for proper sample handling and drying conditions, play a significant role in the collection process. While it is important that the blood doesn't need to fill the entire circle, optimal positioning is still necessary for reliability. Exposure to direct sunlight can degrade the quality of the sample, leading to inaccurate results, and preventing contact with other wet surfaces minimizes contamination risks. Therefore, focusing on even soaking aids the integrity and reliability of the blood samples collected.