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CLS416 Clinical Hematology I Rot I Auto Unit Auto Cell Counting Instruments Handout

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AUTOMATED CELL COUNTING ANALYZERS Multi-parameter cell counters can measure, derive and/or calculate CBC parameters, WBC types and reticulocytes. Most possess autosampling with barcode identification, system status monitoring, and computer-enhanced data analysis with computer storage of patient and control data capabilities. Cell distribution graphs, as well as sample and instrument flagging systems, are standard features; alarms may be visual or audible. Cell counters use two main principles of operation for cell counting and sizing......optical scatter and electronic impedance (or modifications). Most hematology analyzers (Abbott, Bayer, Beckman-Coulter, Sysmex) use a combination of technologies. A. Optical scatter = Light Scatter:

These instruments utilize the process of flow cytometry in which a thin stream of cells are injected into a flow cell with a light beam, most often a laser. 1. As cells pass through the laser, light is scattered light

hits the cell and changes direction. The scattered light hits photodetectors which convert the light signals into electrical signals.

2. The number of signals indicates the number of cells,

optical counts, and the angle of light scattered when striking a cell depicts cell size and/or yields information about cellular characteristics:

a. Forward angle light scatter = cell size b. Side angle light scatter = cell granularity or structures B. Coulter Electronic Impedance = Direct current (DC) Resistance:

These instruments are based on the electrical conductivity difference between cells and diluent. Cells do not conduct electricity. 1. Blood cells are suspended in a fluid that conducts

electricity. The cells are drawn through an aperture (small hole), simultaneously with a low voltage direct current passing between two electrodes (a transducer).

2. The passage of each cell increases the resistance of

the electrical path between the two electrodes cells impede (break) the current generating a voltage pulse the size of the impedance change.

3. The number of pulses generated indicates

the number of cells, impedance counts, and the height or amplitude of the voltage pulse depicts cell size/volume.

4. Pulses are selected and classified according to size by a pulse-height

analyzer (PHA).


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C. Definitions:

Cell coincidence Cell coincidence is an inherent error that affects all impedance methods of cell counting. Two or more cells passing through an aperture at one time may generate a single voltage pulse and therefore be counted as one cell. Since this could result in falsely low counts, cell counts are automatically corrected for this occurrence. Cell coincidence is mathematically predictable based on cell concentration.

Hydrodynamic focusing = Focused Flow Both optical and impedance methods of cell counting employ hydrodynamic focusing

(focused flow). Laminar flow is induced by injecting a slow-moving sample dilution into a stream of fast-moving sheath fluid which prevents mixing. The sheath fluid surrounds the diluted sample and narrows it so that cells flow through the sensing zone in single file…this process is known as hydrodynamic focusing. Focusing reduces cell coincidence, helps avoid protein buildup on aperture systems and keeps cells in the center of the sample stream.

Thresholds = Discriminators Thresholding is used for both impedance and optical counting systems to determine events to accept for analysis. Thresholds are electronically set size limits that exclude unwanted particles (below the threshold) and allow the selection of particles to be analyzed (above the threshold). Thresholds also distinguish between cell types (such as red cells and platelets) and sort cells within a population into subgroups (WBC types).

Thresholds, also called discriminators, may be permanently set or float so that the optimum threshold setting is determined for each sample. Single lower thresholds are used for some measurements while a combination of lower and upper thresholds are used for others. In certain instances, an event must meet the criteria of three thresholds to be included in the analysis. Additionally, editing may be used to eliminate unusual/aberrant pulses or signals that do not truly represent the cell type being analyzed. Threshold examples: Impedance WBC: lower ~35 fl, no upper; red cells are lysed. Impedance RBC: lower ~35 fl, no upper; # of WBCs present during RBC count is usually insignificant. Impedance PLT: lower ~2 fl, upper threshold floats.


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HISTOGRAMS OR SCATTERPLOTS ARE GENERATED:

D. Histogram A one-dimensional graphic representation of cell number versus ONE measured cell property (usually cell size)…a frequency curve. Cells are channelized by size and the number of particles (Y-axis) versus the size of particles (X-axis) are plotted against each other. The data displayed in size-distribution histograms is most frequently obtained using electrical impedance; depicts cell number within a size range, the mean size/volume of cells counted or the distribution of cells around the mean size.

E. Scatterplot/scattergram/cytogram

Two-dimensional graphic representations of TWO (or more) cell properties or characteristics plotted against each other (e.g., cell size and internal cell structures such as granules or lobes). Cell types appear as clusters and the number of dots in each cluster denotes the concentration of that cell type (dot plot).

The data displayed in scatterplots is generally obtained using a combination of technologies,

including light scatter; cluster analysis differentiates and quantitates cell types. F. Both histograms and scatterplots have normal/expected cell distribution/scatter patterns:

WBC, RBC & PLT HISTOGRAMS

Graphic display of relative cell number on the Y axis plotted against cell size (one cell property) on the X axis. Normal cell distribution patterns begin at baseline (few cells), followed by a peak of cells as cell concentration increases, then return to baseline.

SCATTERPLOTS/SCATTERGRAMS

Graphic display of one cell property (e.g., cell size) on the Y axis plotted against a second cell property (e.g., internal cell structures) on the X axis. The density of dots in each cluster represents cell concentration. Cluster location indicates cell type (per methodology).


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INSTRUMENT PARAMETERS: SOURCE OF DATA: To correctly interpret cell data, particularly when resolving a sample ‘problem’ or troubleshooting an instrument malfunction, it is necessary to know how each parameter on the automated cell counter is obtained (i.e. methodology) and if the parameter is directly measured, derived or calculated. Refer to site-specific instrument handout or procedure/operator’s manual for this information. Parameters may be: • Directly measured using optical scatter (optical counts), electrical impedance (impedance counts)

or photometric measurements - HGB is always measured photometrically, usually using a modified cyanmethemoglobin method.

• Derived from computerized analysis of histograms or scatterplots/scattergrams. • Calculated - MCH and MCHC are computed from other parameters by all instruments. On most automated hematology analyzers: • Reagent systems lyse the red cells to analyze WBCs and measure hemoglobin concentration. • Red cells and platelets are counted together. • MCV is the average/mean cell volume of all RBC sizes in a population of red cells. • RDW is red cell distribution width, an index of red cell size variation that correlates to the amount

of anisocytosis present. The S.D. of the RBC histogram is determined and then the C.V. is calculated. RDW is most frequently reported in %, the coefficient of variation.

• MPV is the mean platelet volume (platelet equivalent of the MCV); the MPV may be increased by the presence of giant platelets or platelet clumps. • Reticulocytes are counted via optical methods using supravital, nucleic acid or fluorescent dyes to

generate the reticulocyte count in percent and absolute number.

• Dual methods of measurement may be performed (e.g., two WBC counts or two platelet counts) to increase count reliability when interference exists.


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ANALYSIS OF HISTOGRAMS AND SCATTERGRAMS: • The RBC histogram can be used to determine the mean red cell volume (MCV) or dispersion of

cells around the average size (RDW). • Mean platelet volume (MPV) is usually obtained from the PLT histogram. • WBC differential scattergram analysis yields data used to identify and enumerate WBC types. The main WBC Diff scatterplot looks similar from instrument to instrument even though the cell properties measured vary; the scattergrams of other cell types (e.g., PLT or RETIC counts) are not comparable.

MCV

RDW

MPV


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AUTOMATED DIFFERENTIAL SYSTEMS: To generate scatterplots and 5-part differentials, adaptations of the basic principles have evolved to classify WBC sub-types. The following methods are used alone or in combination: • Electronic impedance/low voltage direct current (DC) resistance determines cell volume. • Light scatter detected at various angles yields data about cell size and cellular characteristics. • Conductivity/Radio Frequency (RF), which is high-voltage electromagnetic current resistance

(radio waves), provides information about internal cell structure/density. • Fluorescence is combined with light scatter to analyze RNA/DNA content. • Cytochemistry combines absorption of enzyme stained cells with light scatter. 1. Abbott Cell-Dyn 1700 - Histogram Analysis Impedance generated pulses are sorted using a series of thresholds and histograms are displayed and analyzed to classify WBC types. A screening 3-part differential is produced. 2. Abbott Cell-Dyn 4000/3500 - MAPSS Technology Scattered light is measured at multiple angles (4) – Multi Angle Polarized Scatter Separation – in an optical flow cell. WBC types are classified and displayed in scatterplots. Analysis yields information about cell size, granularity, complexity (internal structure) and lobularity. A 5-part differential is generated 3. Coulter GEN-S and LH series - VCS Technology Three measurements – Volume, Conductivity and Scatter – are performed simultaneously in an electro-optical flow cell. Volume is measured using impedance, conductivity analyzes internal cell characteristics, and light scatter analyzes external surface characteristics/granules. Information is gathered to classify WBC types and scatterplots are displayed. A 5-part diff is generated. 4. Sysmex XE series - Flow Cytometry with Fluorescence and RF/DC Technology

Cell analysis in a flow cytometer that detects forward light scatter (cell size), side scatter (internal cell structures) and side fluorescent scatter (RNA/DNA content) is combined with radio frequency (RF) and direct current (DC) measurements to identify WBC types and display scattergrams. A 5-part differential is generated.

5. Bayer Advia series – Flow Cytometry with Cytochemistry Determination of cell type is done by selectively staining cells based on enzyme components (peroxidase) and analyzing cells in an electro-optical flow cell. Scattered light (cell size) and light absorption (staining intensity) are used to classify WBC types and display cytograms.

A 5-part differential is generated.

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Neuts Monos

Lymphs

2100

RBC ghosts

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Monos

Eos

Lymphs

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Neuts

Monos

Lymphs

Scatter

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Bayer ADVIA 120

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Neuts

Lymphs

Monos

Debri

Absorption


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SPECIMEN REQUIREMENTS Testing critically depends on the quality of the specimen. The best sample is collected atraumatically and meets the minimum draw requirements for each size of EDTA tube or microtainer draw as per laboratory protocol. Always check the sample for proper labeling and check visually for clots by tilting.

Ideally, the sample is processed within 4 hours of blood draw (particularly if a smear is required); for specific time limits, follow laboratory specimen requirements. Changes associated with old samples mainly affect the WBC count & Diff (increased #’s of dying WBCs) and MCV (RBCs swell with age). REAGENTS Fully automated analyzers monitor reagent levels. For the reagents specific to each parameter, see site handout and/or your institution procedure manual. Reagents are stable until the stated expiration date and must be handled following manufacturer instructions. QUALITY CONTROL Tri-level commercial controls are purchased from the manufacturer; manufacturer instructions for handling must be adhered to. Control results are flagged when they fall out of range and can be displayed on Levey-Jennings charts to assess accuracy and precision. Controls are run: • To periodically monitor the performance of the testing system. See site procedure manual/handout

for the control frequency policy followed at your institution. • After a reagent change if that is site policy. • When troubleshooting an instrument problem or following maintenance procedures. MAINTENANCE Routine maintenance is necessary to ensure proper instrument functioning. All instruments need to be maintained according to manufacturer’s recommendations, including required daily instrument checks and cleaning of analyzer components. See site procedure or maintenance manual for daily instrument maintenance and scheduled weekly or monthly preventive maintenance requirements. BACKGROUND CHECKS Background counts must be done at least once daily and are performed following daily cleaning procedures. Backgrounds are checked after a reagent change if that is site policy (based on manufacturer’s recommendations). Backgrounds counts must fall within established acceptable limits. CALIBRATION SCHEDULE Instrument calibration with a commercial Calibrator (with known reference values) should be done every six months or sooner if needed, e.g., following replacement of a major instrument component.

TROUBLESHOOTING All persons operating the instruments should know the location of the Operator’s Manual which contains information such as instrument description, principles of operation, required maintenance, calibration protocol, and a routine troubleshooting section. This manual should be referred to in the event of instrument malfunction. Some steps to take when troubleshooting include: • Check for alarm messages • Confirm that cleaning procedures and scheduled QC monitoring has been done and is acceptable. • Try to eliminate various components of system:

o Reagents – quality, quantity (alarm messages), delivery of reagents o Electronic – usually requires attention of customer service o Pneumatic – vacuum or pressure leaks will affect transfer of fluids

The operator should know the location of the technical service phone number to request service for problems that cannot be resolved after troubleshooting.


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TESTING VARIABLES Strict adherence to laboratory protocols is vital to prevent erroneous results caused by:

• Pre-analytical variables (sample collection and processing) Specimen integrity is vital for accurate cell count results. Clotting, hemolysis (in vitro) or specimen contamination, to name a few, may compromise CBC/Diff and Retic results. A partially clotted sample invalidates all results and requires a sample redraw.

• Analytical variables (reagents, instrumentation, equipment, technique) Due to the many variables that may cause instrument or reagent related errors, it is imperative that commercial controls are used to continuously monitor the testing system. Reagent and/or control problems can arise if manufacturer recommendations for handling are not followed. The operator should be aware of invalid results caused by interfering substances (e.g., elevated lipid levels) and must adhere to instrument linearity limits. • Post-analytical variables (reporting results) Patient values should be correlated with clinical information (if available) before reporting. All laboratories establish critical/panic values that must be verified and/or action taken per lab policy. Questionable results must be investigated before reporting, e.g., inconsistent values (Hgb does not match the Hct) or results that fail a delta check with previous results. Delta checks are designed to detect discrepancies in results before reporting by comparing current patient values to previous patient values. Delta check limits define the allowable difference in consecutive results of a specific test for the same patient within a certain time period. The delta limit should be set so that true changes in test results (i.e., correct results) are not flagged as delta check failures. When delta check limits are exceeded (fail delta), a potential error exists that may involve specimen collection or a change in the patient’s clinical condition.

EVALUATE THE FOLLOWING CBC RESULTS. ARE RESULTS REPORTABLE? (1) (2) (3) (4) WBC (K/uL) 6.9 WBC 9.7 WBC 57.3 WBC 0.5 RBC (M/uL) 4.69 RBC 1.96 RBC 2.36 RBC 2.68 HGB (g/dL) 14.6 HGB 6.8 HGB 8.2 HGB 8.5 HCT (%) 44.0 HCT 19.6 HCT 21.4 HCT 25.0 MCV (fl) 93.8 MCV 100.1 MCV 89.8 MCV 93.3 MCH (pg) 31.1 MCH 34.7 MCH 34.5 MCH 31.7 MCHC (%) 33.2 MCHC 34.7 MCHC 38.4 MCHC 34.0 RDW (%) 12.7 RDW 13.6 RDW 15.7 RDW 15.4 PLT (K/uL) 217 PLT 102 PLT 54 PLT 4 (1) All parameters are reportable, no action is required….Hgb &Hct match, MCHC not >36%, no parameters outside linearity, no critically abnormal results. (2) Critical low Hgb and Hct values; H&H match; verify/call if not previously critical^.

May need a sample redraw to confirm results (possible sample contamination). (3) Critical high WBC, verify/call if not previously critical^; H&H do not match and MCHC is >36%,

do not report until H&H problem is resolved^. (4) Critical low WBC and PLT count; check instrument linearity limits for WBC and PLT (may need to do a manual cell count); verify/call if not previously critical^.

^Handle per institution protocol.


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LIMITATIONS OF AUTOMATED INSTRUMENTS

Each instrument has limitations related to methodology that are defined in the operator’s manual. Multi-parameter instruments have "flagging" analysis programs to identify variations from expected or normal cell distribution patterns and generate ‘suspect flags’ which alert the operator to interference that could render a flagged count incorrect or to sample abnormalities that require blood smear verification.

• When test validity is in doubt, the result(s) can be verified by a smear exam (manual diff, RBC morph, WBC/PLT estimate) or by a manual method (manual WBC, PLT, Retic count or spun Hct).

• Alert flags/messages are instrument or user defined. Each institution establishes its own criteria for: o an automated versus manual differential based on flags and/or numerical data o the corrective action required for a particular flag o the value and action required to confirm an abnormal parameter

CHECKS AND ACTIONS DONE TO VERIFY VALIDITY OF RESULTS BEFORE REPORTING:

• Evaluate all available parameters for data correlation, even if only 1 or 2 are ordered.

• Check that all parameters are within linearity^^ - dilute into linearity or verify manually.

• Handle correctly any critical values^^ and/or parameters that fail a delta check^^. o Significant changes in MCV or RDW values suggest a sample identification problem exists.

• Repeat unbelievable results – rule out a sample aspiration error.

• Check that HGB and HCT values match. o The H&H may not match due to interference by lipemia/bilirubinemia or a WBC count over

linearity, the presence of a cold agglutinin, or partial sample aspiration by instrument.

• Check that MCHC is <36.0%; if not, rerun^^. Correct error if problem persists. A valid cause for an MCHC value >36.0% is spherocytes; a more usual cause is poor H&H agreement. Be cautious about MCHC values <31.0% with a normal or high MCV value as this is an unusual finding.

• Review histograms and/or scatterplots for abnormal cell distribution or "bad" scatter and correlate with numerical data….flags will generally be present when distribution patterns are abnormal.

• Check for flags that require a manual differential, smear review for RBC morphology or WBC/PLT estimate to confirm questionable results^^.

CONDITIONS THAT MAY INTERFERE OR PRODUCE ERRORS IN AUTOMATED PARAMETERS^^: WBC: NucRBC's; presence of unlysed red cells; clumped platelets; giant platelets RBC: RBC agglutination; MCV below linearity; hemolysis HGB: Gross lipemia or bilirubinemia; WBC count over linearity MCV: RBC agglutination; hemolysis PLT: Schistocytes; microcytic red cells; anucleate cytoplasmic fragments; giant platelets or

clumped platelets (may cause high MPV); platelet satellitism; hemolysis RETIC: Interference by red cell inclusions (Howell-Jolly or pappenheimer bodies) ^^Refer to site-specific instrument handout or procedures for linearity limits, critical values and specific errors & their resolution, as well as instrument flags.

A “perfect” CBC has Hgb and Hct values that match with an ‘ideal’ MCHC value of 32.0-36.0%. Most patients will fall in this group. For those patients with an “imperfect” CBC, the next step is identifying the cause and correcting the problem so that the most accurate Hgb and Hct results are reported. NOTE: A reportable MCHC value is set by each laboratory and this will dictate the point at which action for an abnormal MCHC is required, e.g., an MCHC value up to 37.0% may be reported without action per institution policy even though H & H agreement is poor.


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EXAMPLES OF PARAMETER INTERFERENCES OR ERRORS Review of histograms and scatterplots can alert the operator to abnormal cell distribution/scatter patterns. The action required is determined by the flag generated and/or based on numerical data.

Normal RBC histogram: Abnormal RBC histograms: WBC scatterplot showing normal WBC scatterplot showing "bad" scatter and well separated clusters scatter and poor cluster separation

• Abnormal RBC distribution would be flagged • Review may be required based on abnormal

MCV or RDW value(s) Action: Smear exam for RBC morphology

• Automated diff results would not be flagged • Auto diff is reportable if all numerical data

is within institution established range • Will ‘autoverify’ if other parameters are

reportable and instrument is capable

• Automated diff results would be flagged and is not reportable

• Also likely that numerical data is outside of range for an automated diff

Action: Manual differential


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EXAMPLES OF PARAMETER INTERFERENCES OR ERRORS Review of histograms and scatterplots can alert the operator to abnormal cell distribution/scatter patterns. The action required is determined by the flag generated and/or based on numerical data.

WBC histogram and scatterplot showing normal cell distribution/scatter pattern: WBC histogram and scatterplot showing interference:

Causes for interference in the WBC count or Differential: • Nucleated red cells • Giant platelets • Unlysed red cells

o ‘Hard to lyse’ red cells include target cells or red cells that contain Hgb S or F • Clumped platelets • Clotted sample Actions: • Manual diff for nucleated red cells; correct the WBC count if indicated • WBC estimate from blood smear to verify automated WBC result

o Perform manual WBC count if estimate does not correlate due to giant platelets or lyse resistant red cells

• Scan smear for fibrin strands or platelet clumps o Redraw sample if clotted o Redraw blood in citrate anticoagulant if EDTA-induced platelet clumping


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EXAMPLES OF PARAMETER INTERFERENCES OR ERRORS Review of histograms and scatterplots can alert the operator to abnormal cell distribution/scatter patterns. The action required is determined by the flag generated and/or based on numerical data. PLT histogram showing normal cell PLT histogram showing interference: distribution: Instrument problems that may affect platelets: debris, bubbles, reagent contamination, electrical interference. Rerun; if problem persists, must correct (can cause false high background counts).

Causes for interference in the PLT count: • Falsely increased platelet result

o Schistocytes or microcytic red cells o Anucleate cytoplasmic fragments o Hemolysis

• Falsely decreased platelet result o Giant platelets o Clumped platelets

• Clotted sample • Heparinized blood • EDTA-induced clumping

o Platelet satellitism (EDTA-induced) Actions: • PLT estimate from blood smear to verify automated PLT result

o Perform manual PLT count if estimate does not correlate due to schistocytes or microcytic red cells, giant platelets or cytoplasmic fragments

• Scan smear for fibrin strands, platelet clumps or platelets sticking to neutrophils o Redraw sample if clotted o Redraw blood in citrate anticoagulant if EDTA-induced

• Redraw sample if blood is heparinized or hemolyzed o Note: A redraw will not resolve the affects of hemolysis that occur in vivo

Red cells & platelets are counted together Particles fall ‘in’ or ‘out’ of platelet counting area


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EXAMPLES OF PARAMETER INTERFERENCES OR ERRORS ERRONEOUS PHOTOMETRIC HEMOGLOBIN RESULTS Suspect when H&H values don’t match and/or MCHC is >36.0%; a flag may be generated. Patient with lipemic plasma Initial results ►To correct the whole blo Results corrected for lipemia

^^For both procedures: First centrifuge an aliquot of the patient’s whole blood.

• Saline replacement (plasma is replaced with saline): Remove all of the plasma from the red cells and add back an equal amount of saline. Mix sample well and run on instrument.

• Plasma Hgb blank: Remove an aliquot of plasma from the red cells. Run a hemoglobin on the plasma to see how much of the hemoglobin value is really "lipemia". The plasma hemoglobin value obtained is used in the following formula: Corrected HGB = original HGB - [(1 - HCT) x plasma HGB blank]

HCT is expressed in decimal form, i.e. if 40.0%, use 0.40 in formula.

Using the example above: Original Hgb = 9.2 g/dl (false high) Hct = 21.4 % 0.214 (decimal) Plasma Hgb blank = 2.3 g/dl

Calculation: Original Hgb – [(1-HCT) x plasma Hgb blank] = Corrected Hgb 1-.214 = 0.786 x 2.3 = 1.8 9.2 (Orig Hgb) – 1.8 = 7.4 g/dl (Hgb corrected for lipemia)

• HGB and HCT values match; MCHC is reportable • MCH and MCHC results are calculated using corrected Hgb value

Causes for a falsely elevated HGB result: • Conditions that cause turbidity/cloudiness interfere with photometric

hemoglobin measurement o Hyperlipemia o Hyperbilirubinemia/icterus o WBC count over linearity (WBCs are normally present at a

concentration that does not interfere with Hgb) o Rarely, hyperproteinemia

Results due to an erroneous HGB: • HGB and HCT do not correlate + 3 because HGB value is falsely

high and HCT value is correct • Both MCH and MCHC falsely high due to calculation using ‘bad’

hemoglobin value Actions: • Can rerun to rule out sample aspiration error • Correct for lipemia or icterus by performing plasma replacement or

plasma Hgb blank procedures^^ • Correct for over linearity WBC count by diluting sample into

linearity; run dilution on instrument and multiply HGB by dilution


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EXAMPLES OF PARAMETER INTERFERENCES OR ERRORS RBC AGGLUTINATION Suspect when H&H values don’t match and/or MCHC is >36.0%; a flag may be generated. 50 year old female with the following lab findings: Cold agglutinin titer -1:512, DAT Polyspecific - 2+, Anti-IgG negative, Anti-C3 positive. Panel showed presence of Anti-IH; patient was A positive. **RBC clumping was visible when tilting the blood tube and macroscopically on the blood smear. Initial results

Results after warming blood @ 37oC The initial blood smear showed irregular RBC clumping microscopically; RBC agglutination was not observed on the smear made after warming. ^^In theory, the MCV value will be falsely high but this is no longer a consistent finding due to the advent of focused flow. Notes: A manual spun hematocrit determination will not be affected by RBC agglutination. For strong cold agglutinins that will not correct after prolonged warming, the saline replacement procedure can be done (the plasma is replaced with warmed saline).

Erroneous results due to RBC agglutination: • RBC falsely low

o RBC clumps counted/sized as single cells & larger pulses • MCV falsely high^^ • HCT falsely low…parallels the RBC count • HGB and HCT do not correlate + 3 because HGB value is

correct (red cells are lysed) and HCT result is falsely low • Both MCH and MCHC falsely high (calculated parameters) Actions: • Warm blood @ 37oC for 15 minutes or more, rerun sample

• RBC & HCT values rise and MCV value falls after warming • HGB and HCT values match • MCH and MCHC results are reportable • Note that the WBC count and HGB value are NOT affected by

RBC agglutination (no significant change before and after warming) since red cells are lysed for these measurements


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