American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

Why is capillary blood acceptable for hemoglobin testing?

1. It is more stable

2. It contains oxygen-carrying red blood cells

3. It has higher glucose levels

4. It is easier to collect

The correct answer is: It contains oxygen-carrying red blood cells

Capillary blood is acceptable for hemoglobin testing primarily because it contains oxygen-carrying red blood cells. Hemoglobin, which is the protein in red blood cells responsible for transporting oxygen, is present in both venous and capillary blood. This characteristic allows tests conducted on capillary blood to provide accurate and relevant information about the hemoglobin levels a patient possesses. In contrast to the other options, stability is not a primary reason for using capillary blood; while it might be easier to collect than venous blood in some instances, the critical factor for hemoglobin testing is the presence of red blood cells themselves. Capillary blood does not inherently have higher glucose levels compared to venous blood, and that characteristic does not influence its suitability for hemoglobin testing. Therefore, the focus on the presence of red blood cells in capillary blood underscores its appropriateness for accurate hemoglobin measurement.