Manual of basic techniques for a health laboratory - libdoc.who.int

284 Manual of basic techniques for a health laboratoryTable 9.6 Normal erythrocyte volume fractions and packed cellvolumes, by age groupAge group Erythrocyte volume fraction Packed cell volume (%)Newborn infants 0.50–0.58 50–58Infants (3 months) 0.35–0.40 35–40Children (5 years) 0.38–0.44 38–44Women 0.37–0.43 37–43Men 0.40–0.50 40–50ResultsReference rangeTable 9.6 shows the reference ranges for different age groups.Low valuesLow values are found in patients suffering from anaemia. In men with anaemia theerythrocyte volume fraction is lower than 0.4 and in women it is lower than 0.37(packed cell volumes of 40% and 37%, respectively).High valuesHigh values are found in cases of loss of plasma, severe burns, dehydration (as indiarrhoeal diseases) and also (rarely) in polycythaemia.Relationship between the erythrocyte number concentration and theerythrocyte volume fractionNormally, there is a linear relationship between the erythrocyte number concentrationand the erythrocyte volume fraction. If the erythrocyte number concentrationis C ¥ 10 12 per litre, the erythrocyte volume fraction will normally be in the range(C - 0.2)/10 to (C - 0.4)/10.Example:If the erythrocyte number concentration is 5 ¥ 10 12 /l, the erythrocyte volume fractionwill normally be in the range (5 - 0.2)/10 to (5 - 0.4)/10; i.e., 0.48 to 0.46.In traditional units, the relationship is similar, but the formula for the calculation isslightly different: if C is the erythrocyte count, the packed cell volume (haematocrit),as a percentage, will normally be in the range (C ¥ 10) - 2 to (C ¥ 10) - 4.Relationship between the erythrocyte volume fraction and thehaemoglobin concentrationNormally, there is a linear relationship between the erythrocyte volume fractionand the haemoglobin concentration. The erythrocyte volume fraction is about 0.003times the haemoglobin concentration when the latter is expressed in grams perlitre. If the haemoglobin concentration is expressed in terms of millimoles ofhaemoglobin(Fe) per litre, the erythrocyte volume fraction is roughly 0.05 timesthe figure for grams per litre.Example:A person with a haemoglobin concentration of 130g/l will normally have an erythrocytevolume fraction of 130 ¥ 0.003 = 0.39. In terms of haemoglobin(Fe), the