MLT GlobeHematology: Hematology methods & instruments – page 2
83 Hematology MCQs on Hematology methods & instruments with answers and explanations.
An automated digital morphology system has pre-classified the white cells on a smear. Before reporting, the correct practice is that:
Digital systems suggest classifications, but a trained person must verify and reclassify cells before results are released. A full manual repeat on every slide is not required.
The sodium lauryl sulfate (SLS) hemoglobin method is widely used on analyzers mainly because it:
SLS lyses red cells and forms a stable SLS-hemoglobin complex that correlates with the cyanmethemoglobin reference method without cyanide waste. Turbidity from lipids or high WBC can still interfere.
In impedance analyzers, platelets are separated from red cells counted in the same aperture by:
Platelets give small pulses (about 2–20 fL) and red cells larger pulses (about 36 fL and above), so volume thresholds separate them. Fluorescent staining is used for reticulocytes and some optical platelet methods.
Türk's solution for manual white cell counts lyses red cells because it contains:
Türk's fluid is dilute acetic acid, which lyses red cells, plus gentian violet, which stains white cell nuclei.
In the Westergren method, the ESR is read after:
The Westergren ESR is the height of the clear plasma column after the tube stands upright for 60 minutes, reported in mm/hour.
The hematocrit (packed cell volume) is:
The hematocrit is the fraction of blood volume occupied by red cells, reported as % or L/L. MCH is hemoglobin per cell and MCV is average cell volume.
A microscope with a 10× eyepiece and a 100× oil-immersion objective gives a total magnification of:
Total magnification is eyepiece × objective: 10 × 100 = 1000×.
Sahli's method estimates hemoglobin by converting it to:
Sahli's method mixes blood with 0.1 N HCl to form brown acid hematin, which is diluted with water until it matches a glass standard.
Daily quality control results for an analyzer are plotted over time on a:
A Levey-Jennings chart plots control values against the mean and SD limits over time, helping to spot shifts and trends. A Price-Jones curve shows red cell diameters.
In fingerstick blood collection, the first drop of blood is wiped away because it:
The first drop contains tissue fluid (and may contain alcohol), which dilutes the sample and gives wrong counts.
Leaving a tourniquet on for several minutes before venipuncture can cause:
Long tourniquet time pushes fluid out of the vein, concentrating cells and large molecules. Tourniquets should stay on for no more than about 1 minute.
A 5-part automated differential reports which cell types?
A 5-part differential sorts white cells into the five normal types. Abnormal cells such as blasts are only flagged and must be checked on a smear.
Once Köhler illumination has been set, which action should NOT be used to reduce image brightness?
Condenser height and aperture are set for resolution and contrast during Köhler alignment; altering them degrades the image. Brightness should be changed with the rheostat or neutral density filters.
A control has an accepted Hb range of 14.0 ± 0.4 g/dL. Five repeat runs give 13.2, 13.3, 13.2, 13.3 and 13.2 g/dL. How should these be described?
The results agree closely (precision) but all fall below 13.6 g/dL, outside the accepted range, indicating systematic error (inaccuracy).
For the best cell morphology, blood smears from an EDTA sample should ideally be prepared within:
Storage in EDTA gradually causes crenation, neutrophil vacuolation and nuclear lobulation changes, so smears are best made within about 2–3 hours, although counts stay stable much longer.
K2EDTA tubes are designed to give approximately what final EDTA concentration when filled correctly?
The recommended range is about 1.5–2.2 mg/mL. Underfilled tubes give excess EDTA, shrinking cells and lowering the hematocrit and MCV.
The blue network seen in reticulocytes stained with new methylene blue represents precipitated:
Supravital dyes precipitate ribosomal RNA into a reticulum, giving reticulocytes their name. Denatured hemoglobin forms Heinz bodies; DNA fragments are Howell–Jolly bodies.
Hydrodynamic focusing in a hematology analyzer is used to:
A sheath fluid narrows the sample stream so cells pass in single file through the center of the aperture or laser beam, reducing coincidence and edge-path errors. Lysis of red cells is done by a separate reagent.
If two cells pass through the impedance aperture at the same time and are not corrected, the result is:
Coincident cells are read as one large pulse, so the count falls and the volume rises. Analyzers apply mathematical coincidence correction to minimise this.
A grossly lipemic sample gives Hb 16.5 g/dL (165 g/L), Hct 36% and MCHC 45.8 g/dL. The best way to obtain a correct hemoglobin is to:
Lipid turbidity falsely raises the optical hemoglobin, so MCH and MCHC are falsely high; plasma replacement removes the turbidity. Warming corrects cold agglutinins, not lipemia.