Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam 2026 - Free Medical Laboratory Science Practice Questions and Study Guide

Rouleaux is a term that describes the phenomenon where red blood cells (RBCs) stack together in a formation that resembles a stack of coins. This occurs due to changes in the blood's plasma proteins, especially the increase in fibrinogen or immunoglobulins, which can lead to increased red blood cell aggregation. In normal conditions, red blood cells move freely in the bloodstream, but under certain pathological conditions, rouleaux formation can be observed.

This stacking is indicative of various medical conditions, including inflammatory processes or multiple myeloma. Recognizing rouleaux is important in laboratory diagnostics because it can influence hematological assessments, such as hemoglobin concentration and the erythrocyte sedimentation rate (ESR).

The other options pertain to different processes: clotting involves the coagulation cascade and platelet activity, agglutination typically refers to the clumping of cells due to antibody actions, and thrombin is a specific enzyme involved in the clotting process but does not relate directly to the stacking of red blood cells. Understanding these distinctions reinforces the importance of recognizing and interpreting various blood characteristics in laboratory settings.