Understanding MCV, MCH, MCHC, RDW, MPV, PCT, and PDW in CBC
🩸 Understanding MCV, MCH, MCHC, RDW, MPV, PCT, and PDW in CBC
A Complete Guide to RBC and Platelet Indices
Complete Blood Count (CBC) is one of the most fundamental yet clinically powerful laboratory tests.
Beyond simple cell counts, RBC indices (MCV, MCH, MCHC, RDW) and platelet indices (MPV, PCT, PDW) provide key diagnostic insights into anemia types, bone marrow activity, platelet function, and inflammatory states.
This article summarizes each parameter, its clinical significance, interpretation tips, and related disorders.
✅ 1. MCV (Mean Corpuscular Volume)
Average size (volume) of a red blood cell
- Unit: fL
- Reference range: 80–100 fL (may vary by laboratory)
🔺 Increased MCV (Macrocytosis)
- Vitamin B12 deficiency
- Folate deficiency
- Liver disease
- Alcohol use
- Hypothyroidism
- Reticulocytosis (bone marrow recovery phase)
🔻 Decreased MCV (Microcytosis)
- Iron deficiency anemia
- Thalassemia
- Anemia of chronic disease
- Lead poisoning
⚠ Interpretation Tips
- MCV > 110 fL strongly suggests megaloblastic anemia.
- Thalassemia trait: MCV ↓ but hemoglobin preserved.
- Reticulocytes (larger cells) can falsely elevate MCV.
✅ 2. MCH (Mean Corpuscular Hemoglobin)
Amount of hemoglobin per red blood cell
- Unit: pg
- Reference range: 27–33 pg
🔺 Increased
- Macrocytic anemia
- Chronic alcohol use
🔻 Decreased
- Iron deficiency
- Thalassemia
- Anemia of chronic inflammation
⚠ Interpretation Tips
- Strongly dependent on MCV → avoid isolated interpretation.
- Microcytic anemias generally show reduced MCH and MCHC.
✅ 3. MCHC (Mean Corpuscular Hemoglobin Concentration)
Hemoglobin concentration within RBCs
- Unit: g/dL
- Reference range: 32–36 g/dL
🔺 Increased
- Hereditary spherocytosis
- Severe dehydration
- Cold agglutinin interference (false increase)
🔻 Decreased
- Iron deficiency anemia
- Thalassemia
- Chronic inflammatory anemia
⚠ Interpretation Tips
- True elevation of MCHC is rare—often an artifact.
- Cold agglutination is a common cause of false high MCHC.
✅ 4. RDW (Red Cell Distribution Width)
Variability in RBC size (anisocytosis)
- Unit: % or SD
- Reference range: 10.9–15.7%
🔺 Increased
- Iron deficiency anemia (very characteristic)
- Megaloblastic anemia
- Mixed deficiency anemia (iron + B12/folate)
- Post-transfusion
- Hemolysis (reticulocytosis)
🔹 Normal RDW
- Thalassemia trait typically shows normal RDW despite low MCV.
⚠ Interpretation Tips
- RDW + MCV combination is highly diagnostic:
- RDW↑ + MCV↓ → Iron deficiency
- RDW normal + MCV↓ → Thalassemia trait
✅ 5. MPV (Mean Platelet Volume)
Average platelet size
- Unit: fL
- Reference range: 7–12 fL
🔺 Increased
- ITP (immune thrombocytopenia)
- Post-hemorrhage or hemolysis
- Myeloproliferative neoplasms
- Inflammatory conditions
🔻 Decreased
- Bone marrow suppression
- Aplastic anemia
- Post-chemotherapy
- Prolonged EDTA storage (artifact)
⚠ Interpretation Tips
- MPV is time- and temperature-sensitive; delays cause false changes.
- Classic ITP pattern: PLT↓ + MPV↑
✅ 6. PCT (Plateletcrit)
Total platelet volume (platelet hematocrit)
- Unit: %
- Reference range: 0.150–0.480%
🔺 Increased
- Thrombocytosis
- Reactive inflammation
- Myeloproliferative disorders
🔻 Decreased
- Thrombocytopenia
- Bone marrow suppression
- Chemotherapy or radiation
⚠ Interpretation Tips
- PCT largely mirrors platelet count.
- Used more in trend analysis than in isolated interpretation.
✅ 7. PDW (Platelet Distribution Width)
Variability in platelet size
- Unit: %
- Reference range: 9–17%
🔺 Increased
- ITP
- Myelodysplastic syndrome / MPN
- Inflammatory diseases
- Post-bleeding recovery
🔻 Decreased
- Uniformly small platelets (bone marrow failure)
- Chemotherapy effects
⚠ Interpretation Tips
- Significant device-to-device variability → focus on trends.
- Must be interpreted together with PLT, MPV, PCT.
📌 Summary Table
| Index | Meaning | Increased | Decreased |
|---|---|---|---|
| MCV | RBC size | B12/folate deficiency | Iron deficiency, thalassemia |
| MCH | Hb per RBC | Macrocytosis | Iron deficiency |
| MCHC | Hb concentration | Spherocytosis | Iron deficiency |
| RDW | RBC size variation | Iron/B12 deficiency | Normal in thalassemia |
| MPV | Platelet size | ITP, recovery phase | Bone marrow suppression |
| PCT | Platelet volume % | Thrombocytosis | Thrombocytopenia |
| PDW | Platelet size variation | ITP, MDS | Bone marrow failure |
🔎 General Interpretation Principles
- Always interpret CBC as a pattern, not individual numbers.
- RBC indices → anemia classification.
- Platelet indices → thrombocytopenia cause, bone marrow activity.
- Preanalytical factors (EDTA delay, cold agglutinins) can alter results.
- Physiologic states (pregnancy, inflammation, bleeding) influence indices.
- CBC indices guide the direction of diagnosis but do not replace confirmatory tests.
📚 References
- Henry’s Clinical Diagnosis and Management by Laboratory Methods, 24th ed.
- Rodak’s Hematology: Clinical Principles and Applications, 6th ed.
- ICSH Guidelines for Hematology Testing.
- Hoffbrand’s Essential Haematology, 8th ed.
- WHO Laboratory Manual for Hematology, 2023 Update.
- CLSI Guidelines for CBC and Platelet Indices.