11.2 Hematology Instrumentation, QC, and Calibration

CMLA III.6.B requires you to follow established quality control procedures and to maintain and calibrate instruments within the laboratory assistant's scope. Chapter 4 already defined calibration versus QC on waived meters. This section applies those rules to hematology: waived hemoglobin photometers, spun microhematocrit centrifuges when the laboratory uses them, waived erythrocyte sedimentation rate (ESR) devices, and awareness that automated cell counters are run by medical laboratory technicians (MLT) and medical laboratory scientists (MLS) (or equivalent qualified testing personnel). A Certified Medical Laboratory Assistant (CMLA) does not independently calibrate a high-complexity hematology analyzer or report a CBC from a clotted ethylenediaminetetraacetic acid (EDTA) tube.

Quick Answer: Mix EDTA by gentle inversion immediately. Visible clots mean reject and recollect for a complete blood count (CBC). Run manufacturer quality control (QC) and instructions for use (IFU) calibration on waived hemoglobin, hematocrit, and ESR devices before patients. Automated cell counters belong to MLT/MLS personnel. Failed QC or calibration takes the device out of service.

What the assistant actually operates

Hematology instrumentation on CMLA is not a core-lab Sysmex-, Beckman-, or Abbott-class counter that you independently start, calibrate, and release. Those analyzers use electrical impedance and/or light scatter to count cells. You should recognize that they exist, that they require mixed unclotted EDTA whole blood, and that qualified testing personnel own calibration, reagent sensors, and result release.

Assistant-scope devices are the ones your standard operating procedure (SOP) and Clinical Laboratory Improvement Amendments (CLIA) certificate assign as waived or otherwise within training:

If you work beside an MLT/MLS hematology bench, assisting may include bringing EDTA tubes to the counter, checking that the tube is labeled and mixed, and running waived backup methods when the SOP says to. Assisting is not owning the analyzer.

Established QC on hematology devices

Quality control verifies that today's system matches its assigned range. It does not set the measurement. Follow the IFU frequency: commonly each day of patient testing, with a new cuvette or strip lot, after the device is dropped or cleaned, and whenever results are questioned—plus any extra interval the SOP lists.

• Waived hemoglobin: run the manufacturer's control levels (often low and high, or the labeled set). An electronic simulator or optical self-test is a function check. It does not automatically replace liquid QC when the IFU still requires liquid controls.
• Microhematocrit: QC may include a control blood, a centrifuge timer/speed check on the maintenance schedule, and a duplicate reading check if the SOP requires it. A centrifuge that never reaches the labeled speed under-packs cells and falsely lowers hematocrit.
• Waived ESR: use the kit controls. A tilted rack, vibration, sunlight, or a clotted specimen is not a control failure you can average away—it is an invalid run.

If any required level is out of range, do not report patient results from that device. Repeat only if the SOP allows a single rerun after a documented handling error (for example, an unmixed control). Persistent failure: new control bottle, new cuvette lot, approved cleaning, then supervisor notification and out-of-service until released. Chapter 4's rule still holds: a pretty patient printout after failed QC is not a reportable result.

Maintenance and calibration in assistant scope

Calibration sets the measurement using materials or lot codes of known value. On waived hemoglobin meters that is often a lot-specific code chip, QR code, or factory-calibrated cuvette. Inserting yesterday's lot chip on today's cuvettes is a failed calibration step, not a time-saver.

Maintenance is cleaning and function checks:

• Wipe blood off the hemoglobin optical window with the approved wipe; unapproved bleach on some optics is off-label (Chapter 5).
• Empty waste, replace batteries, run the power-on self-test.
• For a microhematocrit centrifuge: clean the bowl after a broken tube, confirm the lid interlock, and perform scheduled tachometer or timer checks the SOP assigns.
• Document date, time, operator, lots, pass/fail, and corrective action.

CLIA 42 CFR 493.1255 (calibration and calibration verification) is written for nonwaived testing and is a director-level program. Recognize the words so you do not confuse them with daily QC. Do not independently perform high-complexity calibration verification on an automated cell counter, do not type a new slope because platelets look low, and do not use expired calibrators.

EDTA mixing and why clotted specimens are rejected

The CBC and most automated cell counts require mixed, unclotted EDTA whole blood. EDTA chelates calcium so the coagulation cascade cannot run, but only if blood meets the additive immediately and completely.

Invert—gentle complete turns, wrist to wrist—the number of times the manufacturer specifies, as soon as the tube fills. Typical teaching counts are about 8–10 inversions for EDTA; the IFU wins if it differs. Shaking shears red cells (hemolysis) and can fragment platelets. Leaving the tube on the wheel at the chair while you label someone else is how microclots form.

A visible clot in EDTA means the specimen is no longer whole blood for cell counting. Platelets and white cells are trapped in fibrin; red-cell counts, hemoglobin, hematocrit, and especially the platelet count are unreliable. Correct action: reject, document, recollect. Do not:

• Fish the clot out with a stick and run what is left
• Pour leftover blood into a new lavender-top tube (the additive ratio is already wrong, and clots remain)
• Ring the clot against the side and call it mixed
• Send it to the automated counter hoping flags will fix it

Even without a visible clot, inadequate mixing allows platelet clumps (pseudothrombocytopenia) and small fibrin strands. The instrument may flag clumps; qualified personnel may request a recollect in citrate for a platelet count per SOP. The assistant's job is prevention: invert now, inspect before loading, and never present a clotted tube as a valid CBC.

Settled, unmixed EDTA is a second trap on waived hemoglobin: cells packed in the bottom give a wildly high or low result depending on which portion you sample. Mix by inversion again immediately before the assay if the IFU says to, without shaking.

Automated counters: awareness, not ownership

Know enough to be a safe neighbor of the hematology analyzer:

• Specimen: labeled EDTA, mixed, unclotted, within the laboratory's stability window (follow PRE04/SOP; do not invent a number AMT did not publish).
• The counter needs its own QC and calibration, performed and reviewed by MLT/MLS personnel.
• Analyzer flags (clumps, interference, abnormal scatter) are not CMLA morphology sign-out. Notify qualified testing personnel.
• A CMLA backup hemoglobin on a waived photometer does not replace a CBC the provider ordered on the core-lab counter unless the SOP explicitly substitutes that waived method.

Scenario

You are opening the waived hemoglobin photometer for clinic. The high control is above the printed range; the low control is acceptable. You do not test the waiting patients. You document, follow the SOP repeat and cleaning steps, take the meter out of service if it does not recover, and notify the supervisor. Meanwhile an EDTA tube for the hospital CBC arrives with a clot in the bottom. You do not deliver it to the automated counter as a favor. You reject it for CBC and arrange a recollect.

Exam traps

• Calling liquid QC calibration, or skipping liquid QC because the electronic check passed.
• Independently calibrating a high-complexity cell counter.
• Running a clotted EDTA as a CBC after picking out the clot.
• Shaking EDTA instead of inverting it.
• Treating a waived hemoglobin meter and an automated CBC counter as the same instrument with the same operator.

QC proves the waived device may be used. Mixing keeps EDTA whole blood whole. Clots end the run. Calibration and counters above assistant scope belong to the IFU and to MLT/MLS personnel.