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

320 Manual of basic techniques for a health laboratoryThere are two main patterns of distribution of different types ofleukocyte:● One pattern shows a majority of lymphocytes (this type is seen in infantsand children under 10 years).● The other pattern shows a majority of neutrophils (seen in newborninfants, children over 10 years and adults).Each type of leukocyte may be reported in terms of its numberconcentration (i.e. number of cells per litre) instead of as a number fraction.The number concentration is calculated by multiplying the numberfraction of a particular type of leukocyte by the total leukocyte numberconcentration.Example:leukocyte number concentration = 5 ¥ 10 9 /lneutrophil number fraction = 0.42neutrophil number concentration = 0.42 ¥ 5 ¥ 10 9 = 2.1 ¥ 10 8 /l.Fig. 9.111 Table for recording thedifferent types ofleukocytesN: neutrophils; E: eosinophils;B: basophils; L: lymphocytes;M: monocytes.Abnormal findings● Neutrophilia is an increased proportion of neutrophils (above 0.65). Itis particularly common in infections.● Eosinophilia is an increased proportion of eosinophils (above 0.05).It almost always suggests a parasitic infection localized in the tissues(e.g. schistosomiasis, filariasis, hookworm, ascariasis). It can also becaused by allergies.Table 9.12 Normal leukocyte type number fractions, by age groupAge groupCell type aNeutrophils Eosinophils Basophils Lymphocytes MonocytesNewborn infants 0.55–0.65 0.02–0.04 0.00–0.01 0.30–0.35 0.03–0.06Infants (up to 0.40–0.48 0.02–0.05 0.00–0.01 0.40–0.48 0.05–0.101 year, excludingnewborns)Infants (1–4 years) 0.36–0.48 0.02–0.05 0.00–0.01 0.44–0.54 0.03–0.06Children (10 years) 0.45–0.55 0.02–0.05 0.00–0.01 0.38–0.45 0.03–0.06Adults 0.55–0.65 0.02–0.04 0.00–0.01 0.25–0.35 0.03–0.06aTo obtain values in traditional units (i.e. as percentages), multiply each value by 100. The differentialleukocyte count is calculated by multiplying the percentage of a particular type of leukocyte (e.g.neutrophils) by the total leukocyte count and dividing by 100.Example:total leukocyte count = 5000/mm 3percentage of neutrophils = 42%“absolute” neutrophil count = (42 ¥ 5000)/100 = 2100/mm 3 .●●●●Lymphocytosis is an increased proportion of lymphocytes (above 0.35 in adultsand above 0.45 in children). It is found in certain virus infections (e.g. measles),certain chronic infections (e.g. malaria, tuberculosis) and some toxic conditions.Monocytosis is an increased proportion of monocytes (above 0.06). It occurs incertain bacterial infections (e.g. typhoid fever, infectious mononucleosis) andcertain parasitic infections (e.g. malaria, kala-azar (visceral leishmaniasis)).Neutropenia is a decreased number of neutrophils. It may occur in certain infections(e.g. sepsis) and some other diseases.Lymphopenia is a decreased number of lymphocytes and may occur in AIDS.