Question 1

A 34-year-old attends for a pre-employment CBC. Every numerical result falls inside the reference interval, but film review turns up several incidental features. Which finding most clearly requires escalation to a pathologist?

Accepted Answer

Two blasts among 100 leucocytes — Circulating blasts are abnormal at any percentage in a well outpatient and cannot be dismissed as an incidental feature, because they raise the possibility of an acute leukaemia or another marrow disorder. Normal automated counts do not exclude this — the analyser may classify blasts within the mononuclear region. The film must be referred for pathologist review and the finding communicated promptly.

Question 2

A regular blood donor's screening film shows most neutrophils with only two nuclear lobes joined by a thin filament, with normal granulation and no abnormality in any other lineage. All counts are normal, and films from the donor's father show the same picture. What does this represent?

Accepted Answer

A benign inherited variant — Bilobed neutrophils with normal granulation, normal counts and an identical picture in a first-degree relative are the hallmark of the inherited Pelger-Huët anomaly, which has no clinical consequence. Recognising it prevents an unnecessary myelodysplasia workup. The finding should be noted so that later films are not misread as an acquired left shift.

Question 3

A CBC from a 71-year-old reaches the laboratory from the emergency department in January. The analyser reports RBC 1.9 ×10¹²/L, MCV 121 fL and MCHC 448 g/L, and the film shows the appearance in the image. What is the appropriate next step?

Accepted Answer

Warm to 37 °C, then re-run — An MCHC above roughly 380 g/L is not physiologically achievable and, with a falsely low RBC count, a falsely raised MCV and visible red cell clumping, points to a cold agglutinin. Warming the specimen to 37 °C disperses the agglutinates so the cells are counted individually and the indices become valid. A fresh tube collected the same way would clump again.

Question 4

An analyser reports a platelet count of 41 ×10⁹/L on an outpatient who has no bruising or bleeding. There is no clot in the tube, and the film shows platelets rosetting around the neutrophils. What should the technologist do?

Accepted Answer

Recollect into sodium citrate — Platelets rosetting around neutrophils is EDTA-dependent satellitism, an in vitro phenomenon that removes platelets from the counted pool and produces a spurious thrombocytopenia in a patient with no bleeding history. Collecting into sodium citrate prevents the reaction; the count obtained is then multiplied by the dilution correction factor of 1.1 before reporting. A manual count on the same EDTA sample would repeat the same error.

Question 5

A 26-year-old has Hb 112 g/L, RBC 6.1 ×10¹²/L, MCV 66 fL, RDW 13.0% and a ferritin within the reference interval. Red cells on the film are uniformly small, with occasional target cells. Which condition do these results most support?

Accepted Answer

Thalassaemia trait — Marked microcytosis with an increased red cell count, a normal RDW and normal iron stores is the classic thalassaemia trait pattern; the Mentzer index here (66 ÷ 6.1 ≈ 10.8) is below 13, which also favours trait. Uniform microcytes with target cells fit a globin chain imbalance rather than an iron-restricted marrow. Confirmation is by haemoglobin HPLC or electrophoresis.

Question 6

CSF obtained from a traumatic lumbar puncture contains RBC 5000 ×10⁶/L and WBC 12 ×10⁶/L. Blood drawn at the same time shows RBC 4.0 ×10¹²/L and WBC 8.0 ×10⁹/L. How should the CSF white cell count be interpreted?

Accepted Answer

Normal after correction — The blood carries one leucocyte for every 500 red cells, so 5000 ×10⁶/L contaminating red cells account for about 10 ×10⁶/L of the CSF leucocytes. Subtracting that from the observed 12 ×10⁶/L leaves roughly 2 ×10⁶/L, which is within the adult reference interval. The apparent pleocytosis is entirely explained by the traumatic tap.

Question 7

A digital morphology system captures the red cell field shown and pre-classifies the cells as fragmented. The patient is 29 years old with platelets of 22 ×10⁹/L and a rising creatinine. What must the technologist do before the differential is released?

Accepted Answer

Verify the cells on the slide — A pre-classification is a proposal that the operator must confirm at the microscope or in the verification screen before it becomes a reported result. That step matters most here, because confirmed schistocytes with thrombocytopenia and renal impairment trigger an urgent call for a suspected thrombotic microangiopathy. Releasing an unverified classification on such a patient risks either a missed emergency or an unnecessary one.

Question 8

A rural site uploads digital blood film images for review at a referral centre. Every captured field was taken from the extreme feathered edge of the smear. What effect will this have on the differential?

Accepted Answer

Large cells are over-counted — Larger leucocytes — monocytes, immature granulocytes and blasts — are carried to the feathered edge and to the lateral margins during smearing, so fields taken only from that zone over-represent them and distort the differential. Representative counting is done in the examination area just behind the edge, where cells barely touch. Images from an unrepresentative zone should be recaptured rather than interpreted.

Question 9

A 3-year-old with severe iron deficiency has an MCV of 55 fL and an analyser platelet count of 780 ×10⁹/L. The film shows marked microcytosis with some red cell fragments, and platelets that look adequate but not increased. What is the most likely explanation for the platelet count?

Accepted Answer

Microcytes read as platelets — Impedance analysers separate platelets from red cells by size, so extreme microcytes and red cell fragments fall into the platelet channel and inflate the count. The film is the arbiter here: platelets that appear merely adequate contradict a count of 780 ×10⁹/L. An optical or fluorescent platelet count, or a manual estimate, should be used instead.

Question 10

A postoperative patient's haemoglobin was 128 g/L at 08:00 and is 74 g/L on a specimen received at 20:00 from the same ward. The patient is haemodynamically stable, the dressing is dry, and a repeat on the same tube gives an identical result. What should be suspected first?

Accepted Answer

Drawn above a running IV line — A delta check this large in a stable patient with no clinical evidence of bleeding points to a diluted specimen, most often drawn from an arm above or through a running intravenous infusion. Repeating on the same tube reproduces the dilution and therefore proves nothing. The correct action is to request a fresh draw from the opposite arm before any result is released.

Question 11

A solubility screening test performed on an 18-year-old gives a turbid suspension that obscures the printed lines viewed through the tube. Kit controls performed as expected. What is required before a result is reported?

Accepted Answer

Confirm by haemoglobin HPLC — A solubility screen only shows that a sickling haemoglobin is present; it cannot separate sickle cell trait from sickle cell disease, nor distinguish Hb S from other sickling variants such as Hb C-Harlem. Definitive identification and quantitation require HPLC or haemoglobin electrophoresis. The screen result is reported only alongside that confirmatory testing.

Question 12

A point-of-care D-dimer cartridge returns a numerical result, but the device's built-in procedural control did not develop. What should be done with the result?

Accepted Answer

Repeat with a new device — A procedural control that fails to develop invalidates the whole test, because there is no evidence that sample flow, reagent activity and reading all worked; the number displayed cannot be trusted in either direction. The run is rejected and the specimen retested with a fresh cartridge, ideally from a different lot. Persistent failures are escalated and the specimen sent for a laboratory D-dimer assay.

Evaluation and Interpretation

Sorting findings that matter from findings that do not

Telling a real abnormality from a specimen or analyser artefact

Reading blood and body fluid results as a whole

Verifying what a digital imaging system shows you

Catching results that cannot be true

Judging kit-based and point-of-care results