Emerging Microscale Technologies for Global Health: CD4+ Counts - Bionanotechnology: Global Prospects - page 129

procedure.and.reduce.the.running.costs,.Becton.Dickinson.developed.a.portable.single-
platform-based.low.cytometer,.i.e.,.FACSCount. 25,26 .This.system.excludes.the.hematology.
analyzer.for.measurement.of.total.white.blood.cells..FACSCount.starts.with.whole.blood.
and. involves. no. lysis. of. red. blood. cells.. Blood. cells. are. irst. labeled. with. luorochrome-
conjugated. monoclonal. antibodies. (MAbs). (anti-CD3 + ,. CD4 + ,. and. CD8 + ),. and. are. then.
introduced.into.a.sheath.low,.in.which.single-cell.low.is.maintained..Upon.exposure.to.
a.monochromatic.light,.luorescent-labeled.blood.cells.are.identiied..Microluorospheres.
provided. by. the. manufacturer. serve. as. a. quantiication. standard. for. counting. absolute.
CD4 + .and.CD8 + .cells,.thus.eliminating.the.need.for.a.hematology.analyzer. 26

6.2.2 Simplified Flow Cytometry for CD4 + Cell Count in Resource-Limited Settings

To. facilitate. CD4 + . cell. count. in. resource-limited. settings,. other. types. of. single-platform.
low.cytometers.were.also.developed,.including.EasyCD4.(Guava),.CyFlow.(Partec),.and.
Pan-leucogating.(Beckman.Coulter).(Table.6.1)..Compared.with.FACSCount,.they.reduce.
the.cost.not.only.on.initial.instruments,.but.also.on.sample.testing..However,.they.can.only.

TABLE 6.1
Comparison.of.Commercial.CD4.Diagnostics.for.Resource-Limited.Settings

Assay Company Methodology Advantages Disadvantages

FACSCount Becton.

Dickinson

Bead-based.
single-platform.
low.cytometry.

Automated.and.well.
established;.as.a.
reference.method

Absolute.CD4.count.only;.
expensive.instrument.
and.high.running.cost

EasyCD4 Guava.

Technology

Capillary-based.
volumetric.low.
cytometry

Low.consumption.of.
samples.and.
reagents;.reduced.
biohazardous.waste;.
portable

Absolute.CD4.count.only;.
expensive.instrument;.
daily.calibration.
required

CyFlow Partec Volumetric.

single-platform.
low.cytometry

Does.not.require.
daily.calibration;.
portable

Absolute.CD4.count.only;.
does.not.differentiate.
between.CD4 + .
lymphocytes.and.
monocytes

Pan-leucogate. Beckman.

Coulter

Dual.platform;.uses.
CD45.and.side.
scatter.to.gate.on.
leukocytes

Can.provide.CD4%;.
day-aged.blood.
samples.can.be.
used;.portable;.can.
be.adapted.to.single.
platform

Daily.quality.control;.
operating.skills.required

Dynal.T4.Quant Dynal.

Biotech

Monocyte.
depletion;.isolation.
of.CD4.cells.with.
magnetic.beads;.
microscopic.
counting.

Reduced.start-up.
costs;.portable

Absolute.CD4.count.only;.
high.cost.per.test;.
limited.throughput;.
underestimates.CD4 + .
counts

Cytospheres Beckman.

Coulter

Manual.counting.
CD4.cells.label.
latex.beads.under.
a.light.microscope

Reduced.start-up.
costs;.portable

Absolute.CD4.count.only;.
expertise.required.to.
distinguish.monocytes.
from.CD4.cells;.limited.
throughput