What is the likely cause of a blood smear that appears too long?

A blood smear that appears too long is typically the result of using a blood drop that is too large. When a larger drop of blood is applied to the slide, it spreads out more than an appropriate-sized drop, extending the length of the smear as the spreader is pulled across the slide. This action distributes the blood over a greater area, resulting in an elongated appearance.

In contrast, if the blood drop were too small, it would not spread adequately, leading to a short smear. The angle of the spreader also significantly affects the smear's appearance, but if the angle is too low or too high, typically the smear would either be too thick or uneven rather than elongated. In essence, the size of the initial blood drop has the most direct correlation with the length of the smear produced.