What is the significance of decreased red blood cell (RBC) count, hemoglobin, and hematocrit in a 77-year-old smoker?

Evaluation of Decreased Red Blood Cell Parameters in a 77-Year-Old Smoker

The decreased red blood cell count, hemoglobin, and hematocrit in this 77-year-old smoker indicate mild normocytic anemia that requires further investigation to determine the underlying cause, with particular attention to age-related factors, smoking history, and potential chronic disease. 1

Laboratory Findings Analysis

The patient's CBC shows:

• Low RBC count: 3.56 million/uL (normal: 4.20-5.80)
• Low hemoglobin: 11.7 g/dL (normal: 13.2-17.1)
• Low hematocrit: 34.9% (normal: 38.5-50.0%)
• Normal MCV: 98.0 fL (normal: 80.0-100.0)
• Normal MCHC: 33.5 g/dL (normal: 32.0-36.0)
• Normal RDW: 11.7% (normal: 11.0-15.0)

These values represent a normocytic anemia (normal MCV with decreased RBC, hemoglobin, and hematocrit). The normal RDW suggests a homogeneous red cell population rather than mixed causes of anemia.

Clinical Significance

This pattern of mild normocytic anemia in an elderly smoker could indicate:

1. Anemia of Chronic Disease/Inflammation:

   • Most likely diagnosis given age and smoking history
   • Associated with chronic inflammatory conditions, malignancies, and chronic infections
   • Characterized by normal MCV and normal RDW 1

2. Early Iron Deficiency:

   • Before microcytosis develops
   • Common in elderly patients due to poor nutrition or occult blood loss

3. Chronic Kidney Disease:

   • Common in elderly patients
   • Leads to decreased erythropoietin production 1

4. Smoking-Related Effects:

   • Smoking can cause falsely elevated hemoglobin due to carbon monoxide exposure
   • The actual anemia may be more severe than laboratory values suggest

Recommended Evaluation

1. Iron Studies:

   • Serum ferritin (most sensitive marker for iron deficiency)
   • Transferrin saturation (< 20% suggests iron deficiency)
   • Total iron binding capacity 1

2. Inflammatory Markers:

   • C-reactive protein
   • Erythrocyte sedimentation rate
   • These help distinguish anemia of chronic disease from iron deficiency

3. Renal Function Tests:

   • BUN, creatinine, eGFR to assess for chronic kidney disease

4. Vitamin Deficiency Screening:

   • B12 and folate levels
   • Consider methylmalonic acid if B12 deficiency is suspected despite normal B12 levels 1

5. Gastrointestinal Evaluation:

   • Occult blood testing
   • Consider endoscopic evaluation if iron deficiency is confirmed

Management Approach

Treatment should be directed at the underlying cause:

1. If Iron Deficiency Confirmed:

   • Oral iron supplementation: 65 mg elemental iron daily
   • Continue for 3-4 months to replenish stores
   • Take on empty stomach or with vitamin C to enhance absorption 1

2. If Anemia of Chronic Disease:

   • Treat underlying condition
   • Consider erythropoiesis-stimulating agents if appropriate

3. If Renal Insufficiency:

   • Manage underlying kidney disease
   • Consider erythropoiesis-stimulating agents if indicated

4. Blood Transfusion:

   • Generally not indicated for this level of anemia (Hgb 11.7 g/dL)
   • Reserve for hemoglobin < 7.0 g/dL or symptomatic anemia 2

Monitoring and Follow-up

• Repeat CBC in 4-8 weeks to assess response to therapy
• Monitor ferritin and transferrin saturation to assess iron stores
• Annual monitoring of hemoglobin levels in elderly patients 1

Important Considerations

• The normal MCV and RDW in this patient suggest a homogeneous red cell population, pointing toward anemia of chronic disease rather than mixed deficiency
• In elderly patients, anemia is associated with increased mortality risk, loss of independent functioning, physical decline, falls, and cognitive impairment 1
• Smoking can mask the severity of anemia by elevating hemoglobin levels through carbon monoxide exposure
• Consider hemodilution as a potential contributor to apparent anemia, especially if the patient has received significant fluid resuscitation 3