Deciding What is Normal and Interpreting a Blood Count

Question 1

What is a reference range

Answer 1

reference range is a range that is derived from a reference population, defined in a precise way e.g. healthy adults between the age of 20 and 60, who have normal kidney function (basically quite specific)

Question 2

What is a normal range

Answer 2

A reference range but less strictly defined

Question 3

How is a reference range determined

Answer 3

1. Samples are collected from healthy volunteers with defined characteristics
2. They’re analysed using the instrument and techniques that will be used for patient samples
3. The data is analysed by an appropriate technique

Question 4

a normal Gaussian distribution allows data to be analysed by determining …

Answer 4

The mean

Question 5

Problems with using a normal range? (3)

Answer 5

• Not all results outside the reference range are abnormal By definition, 5% of healthy people are excluded (2.5% at either end)
• Not all results within the normal range will be normal for that specific patient
• A result within the 95% range determined from apparently healthy people may still be bad for your health e.g. serum lipids in the upper end of the range are common in western populations

Question 6

MCH?

Answer 6

mean cell haemoglobin

Question 7

MCHC

Answer 7

= MCH conc.

Question 8

RDW

Answer 8

= Red cell distribution width (measures anisocytosis)

Question 9

PLT=

Answer 9

platelets

Question 10

MPV=

Answer 10

mean platelet vol.

Question 11

NE=

Answer 11

neutrophil count

Question 12

LY=

Answer 12

lymphocyte count

Question 13

MO=

Answer 13

monocyte count

Question 14

EO=

Answer 14

eosinophil count

Question 15

BA=

Answer 15

basophil count

Question 16

What is MCH equation

Answer 16

amount of haemoglobin in a given volume of blood divided by the number of red cells in the same volume (Hb divided by RBC)

Question 17

How to measure Hct/PCV

Answer 17

centrifuge

Question 18

What is MCHC equation

Answer 18

amount of haemoglobin in a given volume of blood divided by the proportion of the sample represented by red blood cells (Hb divided by PCV)

Question 19

2 conditions that highlight the difference between MCH and MCHC

Answer 19

 Iron deficiency (or any defect in haemoglobin synthesis) = reduced MCH and MCHC
 Red cell fragmentation= reduced MCH, normal MCHC

Question 20

How is MCHC measured nowadays

Answer 20

electronically on the basis of light scattering

Question 21

what is polycythaemia

Answer 21

Increased RBC count

Question 22

2 steps of evaluating polycythaemia

Answer 22

1. Clinical history and physical examination (splenomegaly, abdominal mass- renal carcinoma, cyanosis)
2. Compare with an appropriate normal range

Question 23

The Hb, RBC and Hct are higher in the X than at other times of life, lower in Y than Z and lower in W than A

Answer 23

X= neonate
Y = children
Z = adults
W = women
A = Men

Question 24

what is PSEUDOPOLYCYTHAEMIA

Answer 24

high Hb, RBC and PCV/Hct an result from decrease in plasma volume,

Question 25

Causes of polycythaemia (5)

Answer 25

• ‘Blood doping’
• Medical negligence
• Can result from the action of erythropoietin that is appropriately elevated (e.g. populations in high altitude)
• Renal or other tumour inappropriately secretes erythropoietin
  ABNORMAL FUNCTION OF THE BONE MARROW

Question 26

polycythaemia treatment?

Answer 26

blood can be removed to thin the blood

- If there is intrinsic bone marrow disease, drugs can be used to reduce bone marrow erythropoiesis

Question 27

What can be used to interpret polycythaemia

Answer 27

CLINICAL CONTEXT

• Young healthy athlete Doping?
• Breathless cyanosed patient Probably hypoxia
• Abdominal mass Could be kidney carcinoma
• Splenomegaly Could be polycythaemia vera