What is the best method to view a blood smear when performing a differential count?

• A. Running a full-screen scan at low power
• B. Random field screens with 10x objective
• C. Battlements technique
• D. Graduated focusing from the top of the smear

Answer: (C)

Systematic sampling across the slide is essential for an accurate differential count. The battlements technique provides a structured, efficient way to scan a blood smear: you move the field of view in stepped, horizontal sweeps across the monolayer area, covering the smear evenly like castle battlements. This pattern helps you sample representative cells, avoid clustering or gaps, and find the uniform region where cells are well separated for counting. Start by locating the monolayer at low power, then switch to higher magnification to identify and count different cell types. Methods that rely on random or uneven scanning can bias the results or miss cells, whereas this battlement approach ensures consistent, comprehensive coverage.