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

What action does sodium polyanethol sulfate (SPS) perform as an additive in blood culture containers?

1. Prevents bacterial growth

2. Enhances clotting

3. Complement inhibition

4. Encourages platelet aggregation

The correct answer is: Complement inhibition

Sodium polyanethol sulfate (SPS) primarily serves as an anticoagulant in blood culture containers, which is essential for isolating microorganisms from blood samples. Its main function is to inhibit complement and phagocytosis, therefore allowing bacteria or fungi present in the blood to remain viable for culture. By doing so, SPS creates an optimal environment for the growth of pathogens, ultimately enhancing the chances of recovery during microbial detection. In this context, complement inhibition is particularly significant because the complement system can engage in opsonization and lysis of pathogens, potentially hindering effective culture growth. Therefore, the inclusion of SPS helps maintain the integrity of the sample, allowing technicians to identify infections more accurately. While other choices mention parameters related to blood components, such as preventing bacterial growth or encouraging platelet aggregation, they do not accurately reflect the role of SPS in blood cultures, which is centered on maintaining microbial viability through complement inhibition.