Red Cell Indices

Nada Mohamed Ahmed ,MD, MT (ASCP)i

Packed Cell Volume

• PCV(haematocrit) is a portion of blood volume occupied by RBC . PCV is needed to detect anaemia. PCV is tested by :centrifugation & read by a haemotacrit reader,

Measurement of Heamatocrit

1 - Collect blood sample in heparinized

capillary tube

2- Centrifuge

3- Read by heamatocrit reading scale

Hematocrit

• Microhematocrit– Centrifuge– Packed cell column

showing separation of cellular components

Normal value

• Refernce Range For PCV• Males 0.40 - 0.54 L/L• Females 0.35 - 0.47 L/L

Male Female Average

PCV % 40-54 35-47 35-54

Clinical Application

Hct (PCV): RBC (polycythemia) plasma volume (hemo-

concentration)

Hct (PCV): RBC (anemia), plasma volume (hem-dilution)

Sources of Error in PCV Testing:

High or low PCV may be due to:1. faulty reading of result .2. inaccurate tubes.3. wrong anticoagulant amount, causes

cell shrinking & swelling.

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• Calculation Of Red Cell Indices

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RBC Indices

RBC indices include: • Mean Corpuscular Volume (MCV).• Mean Corpuscular Haemoglobin (MCH).• Mean Corpuscular Haemoglobin

Concentration (MCHC).

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MCV

• Mean cell volume• MCV is average size of RBC• MCV = Hct x 10

RBC (millions) • If 80-100 fL, normal range, RBCs considered

normocytic• If < 80 fL are microcytic• If > 100 fL are macrocytic • Not reliable when have marked anisocytosis

.

Value:

• MCV provides good assessment of RBC size, It detects :

• microcytosis, found in iron deficiency & thalassaemia.

• macrocytosis, found in B12 & folate deficiency

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MCH

• MCH indicates the mean of Hb content in RBC.

• MCH is average weight of hemoglobin per RBC.

• MCH = Hgb x 10 RBC (millions)

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MCHC• MCHC is average hemoglobin concentration

per RBC • MCHC = Hgb x 100

Hct (%) • If MCHC is normal, cell described as

normochromic • If MCHC is less than normal, cell described as

hypochromic • There are no hyperchromic RBCs

Value:

• MCHC is reflect the concentration of Hb in RBC.

• MCHC is used to differentiate normochromic from hypochromic anaemia

Always correlate RBC morphology with RBC indices .

• Re - check results in discrepancy .• MCHC is better determined than MCH,• This is because PCV measurement is more

accurate than RBC count.

Sources of Error in RBC Indices :

• All errors of RBC, PCV & Hb, cause wrong results in RBC indices.

REFERENCE RANGE FOR ERYTHROCYTE INDICES

MCV 80 – 100 fL

MCH 27 – 32pg

MCHC 32 – 36 %

Value Formula Normal Range

MCV (ƒl)

MCH (pg)

MCHC (x 100%w/v)

PCV (%) x 10RBC (millions / mm3 )

Hb (g/100ml) x 10RBC (millions / mm3 )

Hb (g/100ml) x 100PCV (%)

(80-100)76 – 96 ƒl

27 – 32 pg

32 – 36%