Identifying the Issues: When Smear Quality Hinders Diagnostic Results
Blood smears are a cornerstone of veterinary hematology, allowing clinicians to examine red and white blood cell morphology, platelet counts, and other vital cellular details. However, not every smear yields the clear, diagnostic-quality results needed for accurate interpretation. Knowing when to start fresh can save time and improve diagnostic accuracy. This guide outlines the key indicators that a blood smear should be remade, helping veterinarians and veterinary technicians maintain the highest standards in patient care.
Signs That a Blood Smear Needs to Be Redone
Each of these smears represent common smear quality issues that lead to poorly or non diagnostic results. If your smear looks like these, it is ideal to remake the smear to maintain diagnostic integrity.
Knowing when to remake a smear helps ensure that your slides consistently provide the clear diagnostic information needed. The table below outlines key indicators that a smear may need to be redone:
| Sign | Description |
|---|---|
| Poor Feathered Edge | The feathered edge appears uneven, streaked, or missing entirely, which can prevent the identification of parasites, platelet clumps, and large cells. |
| Uneven or Thick Smear | The smear is too thick throughout or shows patchy cell distribution, making it difficult to evaluate individual cell morphology. |
| Poor Staining Quality | Cells appear too dark, too light, or unevenly colored due to an improperly prepared smear rather than the staining process itself. |
| Presence of Artifacts | Air bubbles, scratches, or debris on the slide can mimic cell abnormalities and hinder accurate interpretation. |
| Insufficient Blood Volume | The smear lacks enough cells for a thorough examination, often due to an overly small drop of blood, which can result in inadequate diagnostic information. |
The Effect of a Poor-Quality Slide on Diagnostic Results
A poorly prepared blood smear can significantly impact the reliability and accuracy of diagnostic outcomes. When a slide is too thick or uneven, cells tend to clump together in areas outside the monolayer. This cell bunching makes it difficult to distinguish individual cell types, obscuring critical morphological details needed for proper identification. The resulting overlap of cells can hide signs of important abnormalities, such as anisocytosis, poikilocytosis, or intracellular parasites.
In addition, an unevenly distributed smear often leads to artificially low cell counts in the readable areas of the slide. Cells that remain trapped in overly thick regions cannot be accurately assessed, and their absence from the monolayer can give the impression of decreased cell numbers. Such distortions compromise the diagnostic quality of the smear, making it harder to draw clear conclusions and potentially delaying proper treatment.
How to Minimize the Need to Remake Smears
While it’s important to know when to start over, prevention is always preferable. Consider the following best practices:
Use a Consistent Technique:
Establish a standard procedure for spreading the smear, including the angle of the spreader slide and the amount of pressure applied.Monitor Blood Volume Carefully:
A small, measured drop of blood (often around 2–3 µL for most species) helps ensure the correct thickness and reduces the chance of an overly dense smear.Keep Slides and Spreader Slides Clean:
Ensuring the slide and spreader are dust- and grease-free prevents artifacts that can compromise smear quality.Practice with Different Species:
Blood from different species (e.g., cats, dogs, birds, reptiles) can behave differently due to variations in viscosity and hematocrit. Adjust your technique accordingly to minimize errors.Double-Check the Feathered Edge Before Staining:
A quick inspection of the smear’s feathered edge can help identify issues early, allowing you to correct them before investing time in staining.
Get the Best Results
Knowing when to remake a blood smear is just as important as the initial preparation. By recognizing the signs of a poor-quality smear—such as a missing feathered edge, uneven thickness, poor staining, or artifacts—veterinary professionals can ensure their slides are clear, diagnostic, and reliable. Following best practices and understanding these indicators will reduce the need for repeated attempts, saving time while enhancing the accuracy of diagnostic results.
