What parameters on the Complete Blood Count (CBC) are affected by rouleaux formation?

CBC Parameters Affected by Rouleaux Formation

Rouleaux formation primarily affects erythrocyte sedimentation rate (ESR) on the CBC, causing falsely elevated values due to increased red blood cell aggregation and faster sedimentation.

Understanding Rouleaux

Rouleaux is a phenomenon where red blood cells (RBCs) stack together in formations resembling stacked coins. This occurs due to:

• Increased plasma proteins (particularly fibrinogen, immunoglobulins)
• Changes in plasma viscosity
• Alterations in RBC surface properties

CBC Parameters Directly Affected

1. Erythrocyte Sedimentation Rate (ESR)

   • Most significantly affected parameter
   • Rouleaux causes accelerated sedimentation of RBCs
   • Results in falsely elevated ESR values 1
   • Different ESR measurement methods (Westergren vs. centrifugation) may show varying degrees of elevation with rouleaux 1

2. Red Blood Cell (RBC) Count

   • May be falsely decreased due to aggregated cells being counted as single cells by automated analyzers
   • Affects accuracy of RBC enumeration

3. Mean Cell Volume (MCV)

   • Can be falsely elevated as aggregated cells may be measured as larger individual cells

4. Red Cell Distribution Width (RDW)

   • May show increased variation due to the presence of cell aggregates

Rheological Effects

Rouleaux formation affects blood rheology by:

• Increasing blood viscosity
• Altering flow dynamics in microcirculation
• Creating abnormal flow patterns that can affect other cell measurements 2

Laboratory Recognition and Resolution

• Rouleaux appears microscopically as RBCs stacked against each other like coins 3
• Can cause confusion in direct agglutination testing
• Saline replacement technique: The established method to resolve rouleaux
  • True agglutination persists when plasma is replaced with saline
  • Rouleaux disappears when plasma proteins are removed 3

Clinical Significance

• Rouleaux formation is associated with conditions causing elevated plasma proteins:

  • Inflammatory disorders
  • Multiple myeloma
  • Macroglobulinemia
  • Other dysproteinemias

• ESR is used as a nonspecific screening test to assess elevations of acute phase proteins in various acute and chronic diseases 1

Important Considerations

• Rouleaux can interfere with blood typing and crossmatching procedures
• In certain conditions like sickle cell disease, rouleaux formation is impaired, resulting in lower ESR values 1
• Temperature affects rouleaux formation and sedimentation rate - higher temperatures increase ESR 4
• The number of RBCs forming rouleaux directly correlates with sedimentation velocity 4

Understanding the impact of rouleaux on CBC parameters is essential for accurate interpretation of laboratory results and avoiding diagnostic errors based on falsely altered values.