Basic Investigations in Haematology Lecture 2 - Packed Cell Volumes (PCV) and Determination of Red Cells Indices Flashcards

A set of 75 English fill-in-the-blank flashcards covering key facts about Packed Cell Volume (PCV) and Red Cell Indices.

Packed Cell Volume (PCV) is the proportion of whole blood occupied by __.

red blood cells

PCV is usually expressed as a __ of the total blood volume.

percentage

PCV may also be referred to as the __.

haematocrit (HCT)

According to the ICSH, the term PCV is used when blood is centrifuged in a __ tube.

capillary

Because of trapped plasma, PCV values are about __ % higher than HCT values.

1–3

A quick rule of thumb is PCV ≈ __ × haemoglobin (g/dL).

3

A raised PCV may be observed in cases of __ such as severe burns or dehydration.

plasma loss

PCV is useful in investigating __ haemorrhagic fever.

dengue

An abnormally high haemoglobin with increased RBC count is called __.

polycythaemia

Examination of plasma above the buffy coat can detect __ in endemic areas.

trypanosomes

After centrifugation, normal plasma is __-coloured.

straw

Colourless plasma suggests severe __ deficiency.

iron

Abnormally yellow plasma indicates __ anaemia due to bilirubin.

haemolytic

Pink-red plasma coloration indicates a __ sample.

haemolysed

White and cloudy plasma is caused by increased __ (lipaemia).

lipids

An increased buffy coat volume reflects elevated __ count.

white blood cell (WBC)

The recommended specimen for PCV is well-mixed __ anticoagulated blood.

EDTA

Capillary blood collected into a __ capillary tube can also be used.

heparinized

Standard microhaematocrit capillary tubes are __ mm long.

75

These tubes have an external diameter of about __ mm.

1

The wall thickness of microhaematocrit tubes is roughly 0.2 – __ mm.

0.25

Capillary tubes with a thin red band are coated with __.

sodium heparin

Tubes with a thin blue band or no band contain __ anticoagulant.

no

Blood is centrifuged at 12 000–15 000 × g for __ minutes to obtain constant packing.

3–5

PCV is determined by comparing the height of the red cell column to the __ column.

total blood

Without a reader, PCV = length of RBC column ÷ length of __ column.

total blood

If PCV exceeds 50 %, centrifuge for an additional __ minutes.

3

Duplicate PCV tests should not differ by more than __ %.

5

Low RCF or short spin time can falsely __ the PCV value.

raise (increase)

Delaying the reading after centrifugation allows plasma to __, raising PCV.

evaporate

Altered red cell shape increases trapped plasma and falsely __ PCV.

raises

In sickle cell disease, PCV may be increased by up to __ %.

20

Excess __ anticoagulant shrinks RBCs and lowers PCV.

EDTA

The preferred form of EDTA for haematology is __-EDTA.

K2

Leaving anticoagulated blood >6 h before testing causes RBCs to __, raising PCV.

swell

Inadequate mixing of blood can cause __ formation and lower PCV.

clot

PCV reference range for newborns is __ %.

44–54

PCV reference range for adult males is __ %.

40–54

PCV reference range for adult females is __ %.

36–46

PCV reference range for infants/children is __ %.

35–45

Severe burns, dehydration, and dengue fever typically __ PCV values.

increase

PCV values are __ in anaemia.

reduced

The quantitative measurements of RBC size and Hb content are called __.

red cell indices

Red cell indices were first introduced by __ in 1929.

Wintrobe

Mean Cell Volume (MCV) measures the average __ of RBCs.

volume

Mean Cell Haemoglobin (MCH) measures the average __ of haemoglobin per RBC.

weight

Mean Cell Haemoglobin Concentration (MCHC) measures the average __ of haemoglobin in packed RBCs.

concentration

Red Cell Distribution Width (RDW) measures the __ in erythrocyte size.

variability

To calculate RBC indices you need Hb, PCV/HCT and __ count.

RBC

MCV = PCV × 10 ÷ __ count.

RBC

Normocytic cells have an MCV of __ fL.

80–100

Microcytic cells have an MCV < __ fL.

80

Macrocytic cells have an MCV > __ fL.

100

With PCV 0.45 and RBC 5 × 10¹²/L, the MCV equals __ fL.

90

MCH = Hb (g/dL) × 10 ÷ __.

RBC count

Normal MCH ranges from __ pg.

28–34

MCH varies directly with the __.

MCV

An increase in MCH may occur in __ deficiency.

vitamin B12

A decrease in MCH is typical of __ deficiency anaemia.

iron

MCHC = Hb (g/dL) × 100 ÷ __.

PCV (Hct)

Normal MCHC range is __ g/dL.

32–36

The only truly hyperchromic erythrocyte with MCHC > 36 g/dL is the __.

spherocyte

Artefactual hyperchromasia can be caused by haemolysis, lipaemia, or numerous __ bodies.

Heinz

If the central pallor exceeds one-third of the cell diameter, the cell is __.

hypochromic

Normal RDW values lie between __ %.

11.5–14.5

An increased RDW indicates __.

anisocytosis

RDW is especially useful when considerable __ in RBC size exists.

variation

RDW is typically __ in thalassaemia minor.

normal

A low MCV combined with a high RDW strongly suggests __ deficiency anaemia.

iron

RBCs with an MCHC of 32–36 g/dL are described as __chromic.

normo

Laboratory professionals correlate indices with Hct, Hb and __ count to detect problems.

RBC

Microhaematocrit tubes fill with blood by __ action.

capillary

In the centrifuge, sealed tube ends must face __ the center.

away from

The buffy coat layer contains leukocytes and __.

platelets

When reading PCV, you should not include the __ coat.

buffy