OSMT (Ontario Society of Medical Technologists) Practice Exam

A blood film that demonstrates "serrated" blood cells:

1. Has been improperly stained

2. Has been improperly fixed

3. Has been made from old blood

4. Has been submerged in a buffer of the wrong pH

The correct answer is: Has been made from old blood

The presence of "serrated" blood cells in a blood film is commonly associated with the age of the blood sample. When blood sits for an extended period, particularly outside of optimal storage conditions, the red blood cells may become damaged and exhibit abnormal morphological features, including serrated edges. This change in cell shape can be attributed to factors such as the degradation of membrane integrity over time and potential changes in osmotic balance as the cells lose water. The other options relate to processes that generally influence how the blood is prepared or preserved. Improper staining could lead to various visual artifacts but would not specifically result in the serrated morphology observed. Likewise, if the cells had been improperly fixed, one would typically see a range of artifacts but not necessarily a consistent serration effect. While an incorrect pH buffer could affect staining or preservation, it does not specifically relate to the serrated appearance that suggests aging or degradation of blood cells. Thus, the observation of this feature points most directly to the blood being old, leading to the correct answer.