Do I need to order a reticulocyte (retic) count separately from a complete blood count (CBC) with differential (diff)?

Reticulocyte Count Ordering in Relation to CBC with Differential

No, you do not have to order a reticulocyte count separately from a CBC with differential, as they are separate laboratory tests that must be ordered individually.

Understanding Laboratory Test Components

A complete blood count with differential (CBC with diff) and reticulocyte count are distinct laboratory tests that serve different diagnostic purposes:

CBC with Differential Components

• Complete blood count (white blood cells, hemoglobin, and platelets)
• White blood cell differential (neutrophils, lymphocytes, monocytes, eosinophils, basophils)
• Red blood cell indices (MCV, MCH, MCHC, RDW)
• Platelet count and indices

Reticulocyte Count

• Measures immature red blood cells
• Assesses bone marrow response to anemia
• Not automatically included in standard CBC with differential 1

Clinical Guidelines for Ordering

Multiple clinical guidelines clearly indicate that reticulocyte counts are separate orders from CBC with differential:

• Guidelines for hematopoietic malignancy surveillance specifically list "CBC w/diff & retic" as a combined surveillance approach, indicating these are separate tests that need to be ordered together 1

• Immune-related adverse event management guidelines specify "CBC with differential and reticulocyte counts" as distinct components of laboratory evaluation 1

• Anemia evaluation guidelines state that reticulocyte numbers "serve to evaluate the appropriateness of the bone marrow response to anemia" but are not automatically included in CBC testing 1

Ordering Practices and Considerations

When to Order Both Tests

Order both CBC with differential AND reticulocyte count when:

• Evaluating anemia to determine if it's due to decreased production or increased destruction
• Monitoring patients with hematologic malignancy predisposition syndromes 1
• Assessing bone marrow function in patients with suspected bone marrow failure 1
• Evaluating patients with suspected hemolysis

When CBC with Differential Alone May Suffice

• Initial screening of patients without specific hematologic concerns
• Monitoring stable patients without anemia
• Routine follow-up of non-hematologic conditions

Common Pitfalls to Avoid

1. Assuming reticulocyte count is included in CBC: Research shows many clinicians don't fully understand which components are included in standard laboratory panels 2, 3

2. Overordering or underordering: Studies show both overutilization and underutilization of CBC components based on clinician understanding 4, 5

3. Missing important diagnostic information: Failure to order reticulocyte count when evaluating anemia can lead to incomplete assessment of bone marrow response 1

4. Inappropriate monitoring: For patients with hematologic predisposition syndromes, guidelines specifically recommend both CBC with differential AND reticulocyte count at regular intervals 1

Best Practice Recommendations

1. Order CBC with differential for routine screening and monitoring

2. Add reticulocyte count when:

   • Evaluating new or worsening anemia
   • Monitoring patients with known hematologic disorders
   • Following patients with predisposition to hematologic malignancies
   • Assessing bone marrow function

3. Consider laboratory system capabilities and reporting structures at your institution, as some advanced hematology analyzers can perform reticulocyte counts simultaneously but still require separate ordering 6

Remember that while both tests provide valuable information about hematopoiesis, they answer different clinical questions and must be ordered separately to ensure complete evaluation of hematologic status.