Page 658 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )
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642 PART 8 ■ Fundamentals of Hematological Analysis
■ echnology continues to deliver new automation capabili- ■ Other cellular applications o f ow cytometry include anal-
ties in hematology. For example, automated reticulocyte ysis o the ratio o cells to B cells in immunode ciency
counting was a leading edge technology a ew years ago states such as AIDS, the study o DNA in cell cycle kinet-
but is a routinely measured parameter in many clinical ics, and the investigation o chromosomes.
laboratories today.
■ Some o the newer instruments prepare and stain periph- Digital Microscopy
eral blood smears and automatically correct or leukocyte
(WBC) inter erence. ■ Advances in arti cial neural networks (ANNs), image
■ Newly developed instrumental capabilities continue to be analysis, and slide handling have combined to produce
developed. Some o the innovations include quantitation o instruments that automate manual di erentials in new
nucleated erythrocyte; a channel or enumeration o imma- ways.
ture granulocytes; random access CD4 lymphocyte counting; ■ echnology, re erred to as automated digital cell morphol-
analysis or CD34, CD38, and CD61 cell markers; measure- ogy, provides an unprecedented level o e ciency and
ment o reticulocyte hemoglobin; enumeration o hemato- consistency.
poietic progenitor cells; and counting immature granulocytes. ■ In its simplest orm, automated digital cell morphology is
a process where blood cells are automatically located and
preclassi ed into categories o blood cells.
Quality Assurance of Instrumental Data
Output ■ Images o these cells are retained or con rmation by a
technologist and can be shared electronically and stored
■ Erythrocyte histograms are valuable in determining the as digital images. T is adaptability allows or uture
similarity o the population o RBCs being tested. review and comparisons by laboratory pro essionals and
■ Quantitative parameters that express variation in the physicians.
erythrocyte population are either the RDW or the RCMI.
T e RDW and MCV can be correlated and classi ed in Instruments in Coagulation Studies
various disease categories. Manual methods have been replaced in the clinical
■ Te WBC histogram classi es WBCs into three catego- ■ hematology laboratory by electromechanical and optical
ries: lymphocytes, mononuclear cells or monocytes, and systems.
granulocytes. Computer programming allows or the di - In the older electromechanical system, two electrodes
erentiation o leukocytes graphically, in terms o percent- ■ work in conjunction with one another. When a ibrin
age and absolute values. strand orms in the plasma-thromboplastin mix-
■ Platelet histograms, the MPV, and the DPW can be gener- ture between these two electrodes, a complete circuit
ated by computer-assisted instruments in addition to the is ormed. Completion o the circuit automatically
platelet count. T e MPV is an expression o the measure stops the timer and the length o the reaction time is
o the average volume o the platelets in the sample. T e displayed.
PDW is a measure o the uni ormity o platelet size.
■ In the optical system, a change in light transmission
through the reaction mixture o plasma-thromboplastin
Laser Technology
is measured as optical density versus time. Formation o a
■ Some systems are based on the principle o di erential brin clot alters the light path, and a er the data are pro-
light-scattering cytochemistry. cessed by the onboard microprocessor, the time in seconds
■ Cytochemical reactions prepare the blood cells or analy- that the reaction took is displayed or printed.
sis, a cytometer measures speci c cell properties, and algo- ■ Both methods can measure AP , P , actor levels, and
rithms convert these measurements into cell classi cation, various other parameters.
cell count, cell size, and hemoglobinization. ■ Platelet aggregation procedures are used to test the
qualitative response o platelets to various aggregating
Applications of Flow Cytometry agents.
■ Instruments based on the f ow-cell cytometry principle Case Studies
were initially designed to count and size cells; later modi-
cations included leukocyte di erential analysis. Because the relationship between histogram and nomogram
■ oday, the applications o the technology are highly in ormation is important to understanding the data output
diverse and include both cellular component identi ca- capabilities o modern instrumentation, speci c examples
tion and cell-sorting capabilities. become important in establishing a diagnosis and monitor-
■ Monoclonal antibodies and f uorescent probes have had a ing treatment o a patient. A knowledge and understanding
major e ect on advances in f ow cytometry applications. o these newer sources o patient in ormation is important to
■ In the hematology laboratory, in addition to leukocyte di - the clinical laboratory scientist. Each o the cases presented
erentiation, applications can include reticulocyte count- in this chapter represents a airly typical example o a speci c
ing and screening or malarial parasites. type o disorder.
