TY  - CHAP
M1  - Book, Section
TI  - Classification of Anemias and Polycythemias
A1  - Lichtman, Marshall A.
A1  - Kaushansky, Kenneth
A1  - Kipps, Thomas J.
A1  - Prchal, Josef T.
A1  - Levi, Marcel M.
PY  - 2011
T2  - Williams Manual of Hematology, 8e
AB  - Clinically  significant  red  cell  disorders  can  be  classified  into:—  Disorders  in  which  the  red  cell  mass  is  decreased  (anemias).  The  principal  effect  is  decreased  oxygen-carrying  capacity  of  the  blood.  They  are  best  expressed  in  terms  of  hemoglobin  concentration.—  Disorders  in  which  the  red  cell  mass  is  increased  (polycythemias).  The  principal  effect  is  related  to  an  increased  viscosity  of  the  blood  (see  Fig.  2–1).  In  addition  to  their  specific  effects,  they  are  best  expressed  in  terms  of  packed  red  cell  volume  (hematocrit).The  red  cell  mass  is  the  volume  of  red  cells  in  the  circulation.—  The  normal  red  cell  mass  of  women  is  23–29  mL/kg.—  The  normal  red  cell  mass  of  men  is  26–32  mL/kg.—  More  accurate  formulas  based  on  body  surface  have  been  recommended.Because  the  red  cells  are  measured  either  as  a  concentration  in  the  blood  as  the  red  cell  count,  the  hemoglobin  content  of  the  blood,  or  the  hematocrit  (packed  red  cell  volume  per  100  mL  of  blood),  rather  than  the  volume  of  red  cells  in  the  total  circulation,  the  anemias  and  polycythemias  can  each  be  subclassified  as:—  Relative,  where  the  red  cell  mass  is  normal  but  the  amount  of  plasma  is  decreased  (relative  polycythemia)  or  increased  (relative  anemia).—  Absolute,  where  the  red  cell  mass  is  increased  (in  true  polycythemia)  or  decreased  (in  true  anemia).It  is  essential  that  the  specific  cause  of  anemia  be  determined.  The  initial  laboratory  approach  to  the  diagnosis  of  anemia  follows.  (Table  2–1).—  Hematocrit,  hemoglobin,  or  red  cell  count  to  determine  degree  of  anemia.  In  most  cases,  these  three  variables  are  closely  correlated.  Hemoglobin  concentration  is  the  most  direct  measure  of  oxygen-carrying  capacity.—  Red  cell  indices  (MCV,  MCH,  MCHC)  to  determine  whether  normocytic,  macrocytic,  or  microcytic  and  normochromic  or  hypochromic  red  cells  are  present  on  average.—  Exaggerated  red  cell  distribution  width  (RDW)  is  a  measure  of  anisocytosis.—  Reticulocyte  count  or  index  to  estimate  whether  marrow  response  suggests  inadequacy  of  red  cell  production  or  an  appropriate  erythropoietic  response  to  hemolysis  (or  acute  bleeding).  The  latter  is  usually  readily  apparent  clinically.—  Examination  of  the  blood  film  to  determine  red  cell  shape,  hemoglobin  content,  presence  of  red  cell  inclusions,  and  accompanying  abnormalities  of  white  cells  and  platelets.—  These  five  studies  should  be  the  prelude  to  guide  further  specific  testing.Important  caveats:—  Red  cell  size  and  hemoglobin  content  is  best  determined  from  their  indices  because  the  blood  film  will  usually  make  evident  only  gross  deviations  (e.g.,  the  need  to  estimate  red  cell  volume  from  a  two-dimensional  area).  Moreover,  the  blood  in  macrocytic  anemia  usually  contains  many  microcytic  cells  and  in  microcytic  anemias,  many  normocytic  cells,  which  make  determination  of  the  average  red  cell  volume  from  a  blood  film  difficult.—  In  general,  the  abnormalities  in  size,  hemoglobin  content,  and  shape  are  approximately  correlated  with  severity  of  anemia.  If  the  anemia  is  slight,  the  other  changes  are  often  subtle.—  Anemia  classically  categorized  as  macrocytic  or  microcytic  may  be  present  in  the  face  of  red  cell  volumes  that  are  in  the  normal  range.  This  may  be  the  case  because  the  anemia  is  so  mild  that  red  ...
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/18
UR  - hemonc.mhmedical.com/content.aspx?aid=1126650942
ER  -