A 31-year-old woman with iron deficiency anemia from heavy periods started oral ferrous sulfate 9 days ago. Today: Hb 92 g/L (9.2 g/dL), Hct 0.30 L/L, RBC 3.95 × 10^12/L, MCV 76 fL and reticulocytes 6.8%, with polychromasia on the film. The laboratory uses a normal hematocrit of 0.45 L/L and these maturation times: Hct 0.35-0.39, 1.5 days; Hct 0.25-0.34, 2.0 days; Hct 0.15-0.24, 2.5 days. It reports a reticulocyte production index (RPI) above 2 as an adequate marrow response. The correct result and conclusion are:

RPI 2.3: an adequate marrow response to the iron

RPI 1.8: an inadequate marrow response to the iron

RPI 4.5: an adequate marrow response to the iron

RPI 5.1: an adequate marrow response to the iron

The corrected reticulocyte count (reticulocyte % × patient hematocrit ÷ normal hematocrit) adjusts for:

The smaller number of red cells in anemia

The early release of shift reticulocytes

Differences in reference ranges by age

Reticulocytes lost in supravital staining

Reticulocyte count and corrections

11 DOH Abu Dhabi (HAAD) lab licensing practice questions on Reticulocyte count and corrections, part of Hematology. The first 11 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A 31-year-old woman with iron deficiency anemia from heavy periods started oral ferrous sulfate 9 days ago. Today: Hb 92 g/L (9.2 g/dL), Hct 0.30 L/L, RBC 3.95 × 10^12/L, MCV 76 fL and reticulocytes 6.8%, with polychromasia on the film. The laboratory uses a normal hematocrit of 0.45 L/L and these maturation times: Hct 0.35-0.39, 1.5 days; Hct 0.25-0.34, 2.0 days; Hct 0.15-0.24, 2.5 days. It reports a reticulocyte production index (RPI) above 2 as an adequate marrow response. The correct result and conclusion are:
1. ARPI 1.8: an inadequate marrow response to the iron
2. BRPI 4.5: an adequate marrow response to the iron
3. CRPI 2.3: an adequate marrow response to the iron
4. DRPI 5.1: an adequate marrow response to the iron
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Answer: C · RPI 2.3: an adequate marrow response to the iron
The corrected reticulocyte count is 6.8 × 0.30 ÷ 0.45 = 4.5%, which adjusts for the reduced number of red cells. At a hematocrit of 0.30, reticulocytes released early from the stimulated marrow need about 2.0 days to mature in the blood, so the RPI is 4.5 ÷ 2.0 = 2.3, an adequate response. A reticulocyte peak about 7 to 10 days after iron is started is the expected sign that the marrow is making hemoglobin again; the Hb then rises over the following weeks. Stopping at 4.5 leaves out the maturation correction, 1.8 uses the 2.5-day time meant for a hematocrit below 0.25, and 5.1 inverts the hematocrit ratio.
- A: The 2.5-day maturation time applies to a hematocrit of 0.15-0.24.
- B: 4.5% is the corrected count before dividing by the 2.0-day maturation time.
- D: This multiplies by 0.45/0.30 instead of 0.30/0.45.
Question 2 · Medium
A manual reticulocyte count by two observers is shown with the patient's hematocrit. Taking 0.45 L/L as the normal hematocrit, the corrected reticulocyte count is:
Figure: MedExams
1. A6.0%
2. B1.8%
3. C3.6%
4. D10.0%
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Answer: C · 3.6%
The two counts agree within acceptable limits, so they are combined: (64 + 56) ÷ 2,000 × 100 = 6.0%. In anemia each reticulocyte is a larger share of fewer red cells, so the percentage is corrected to a normal hematocrit: 6.0 × 0.27 ÷ 0.45 = 3.6%. The reticulocyte production index divides this again by the maturation time, which is about 2 days at this hematocrit. The corrected count shows how well the marrow is responding to the anemia.
- A: 6.0% is the uncorrected percentage.
- B: 1.8% further divides by a maturation time of 2 days, which gives the production index.
- D: 10.0% inverts the hematocrit ratio (0.45 ÷ 0.27).
Question 3 · Medium
A patient has an RBC count of 2.60 × 10^12/L, a hematocrit of 0.24 L/L and reticulocytes of 5.0%. What is the absolute reticulocyte count?
1. A1,300 × 10^9/L
2. B13 × 10^9/L
3. C69 × 10^9/L
4. D130 × 10^9/L
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Answer: D · 130 × 10^9/L
Absolute count = reticulocyte fraction × RBC count = 0.050 × 2.60 × 10^12/L = 0.13 × 10^12/L, which is 130 × 10^9/L (130 × 10^3/µL). The absolute count already reflects the low red cell count, so no hematocrit correction is applied to it. Applying one anyway gives 69 × 10^9/L. Decimal errors in converting the percentage give 13 or 1,300.
- A: 1,300 uses 50% instead of 5.0%.
- B: 13 uses 0.5% instead of 5.0%, a decimal error.
- C: 69 wrongly applies a hematocrit correction to the absolute count.
Question 4 · Medium
The corrected reticulocyte count (reticulocyte % × patient hematocrit ÷ normal hematocrit) adjusts for:
1. AThe early release of shift reticulocytes
2. BDifferences in reference ranges by age
3. CReticulocytes lost in supravital staining
4. DThe smaller number of red cells in anemia
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Answer: D · The smaller number of red cells in anemia
The reticulocyte percentage is reticulocytes per 100 red cells. In anemia there are fewer mature red cells, so the same reticulocyte output gives a higher percentage. Multiplying by the patient's hematocrit over a normal hematocrit (often 0.45) removes this effect. The second correction, for shift reticulocytes that circulate longer, is the extra step in the reticulocyte production index.
- A: The shift correction is the extra step in the reticulocyte production index.
- B: Age-related ranges are not part of the formula.
- C: Reticulocytes are not lost by supravital staining.
Question 5 · Hard
A woman with warm autoimmune hemolytic anemia has a hematocrit of 0.21 L/L (21%) and reticulocytes of 15%. Normal hematocrit is 0.45; maturation times are 1.0 day at 0.40-0.45, 1.5 at 0.35-0.39, 2.0 at 0.25-0.34 and 2.5 at 0.15-0.24. What is her reticulocyte production index?
1. A6.0
2. B3.5
3. C2.8
4. D7.0
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Answer: C · 2.8
First correct for the low hematocrit: 15% × 0.21 ÷ 0.45 = 7.0%. Her hematocrit falls in the 0.15-0.24 band, so the maturation time is 2.5 days, and 7.0 ÷ 2.5 = 2.8. The RPI shows production nearly three times normal, a strong marrow response to hemolysis. Each wrong answer comes from skipping or misreading one step.
- A: 6.0 divides by the maturation time but skips the hematocrit correction.
- B: 3.5 uses 2.0 days, the maturation time for a higher hematocrit.
- D: 7.0 is the corrected count before dividing by the maturation time.
Question 6 · Hard
A 50-year-old man has hemoglobin 72 g/L (7.2 g/dL), hematocrit 0.22 L/L, RBC 2.40 × 10^12/L and reticulocytes 2.8% (reference 0.5-2.5%; absolute count reference 25-100 × 10^9/L). What best describes his red cell production?
1. AAdequate, since the percentage is above range
2. BNormal, since the absolute count is in range
3. CInadequate for the degree of anemia
4. DIncreased, as expected in hemolysis
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Question 7 · Hard
A traveller with Plasmodium falciparum malaria (parasitemia 9%) has an automated fluorescent reticulocyte count of 6.8%. A manual new methylene blue count on the same sample is 1.4%. What most likely explains the difference?
1. AParasite nucleic acid takes up the fluorescent dye
2. BRing forms are counted as reticulocytes manually
3. CHemolysis in the tube lowers the manual count
4. DInfected cells lose their RNA in manual staining
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Question 8 · Hard
A manual reticulocyte count uses a Miller disc, whose small square is one-ninth the area of the large square. Over successive fields, 120 red cells are counted in the small squares and 27 reticulocytes in the large squares. The reticulocyte percentage is:
1. A0.025%
2. B2.5%
3. C2.7%
4. D22.5%
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Question 9 · Easy
After release from the bone marrow, a reticulocyte normally circulates for about how long before it becomes a mature red cell?
1. A2 weeks
2. B1 day
3. C4 hours
4. D4 days
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Question 10 · Medium
A 45-year-old woman has hemoglobin 82 g/L (8.2 g/dL) and a reticulocyte production index (RPI) of 1.1. The laboratory takes an RPI above 3 as an adequate response and below 2 as inadequate. This result indicates:
1. AAn inadequate marrow response to the anemia
2. BAn adequate response, as in hemolysis
3. CA borderline response needing a repeat
4. DAn adequate response, as after bleeding
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Question 11 · Medium
On a new methylene blue preparation, which finding qualifies a red cell to be counted as a reticulocyte?
1. ADiffuse blue-gray staining of the cell
2. BPale blue-green bodies at the membrane
3. CTwo or more blue granules or a network
4. DA single round, dark blue body
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Reticulocyte count and corrections

A manual reticulocyte count by two observers is shown with the patient's hematocrit. Taking 0.45 L/L as the normal hematocrit, the corrected reticulocyte count is:

A patient has an RBC count of 2.60 × 10^12/L, a hematocrit of 0.24 L/L and reticulocytes of 5.0%. What is the absolute reticulocyte count?

The corrected reticulocyte count (reticulocyte % × patient hematocrit ÷ normal hematocrit) adjusts for:

A woman with warm autoimmune hemolytic anemia has a hematocrit of 0.21 L/L (21%) and reticulocytes of 15%. Normal hematocrit is 0.45; maturation times are 1.0 day at 0.40-0.45, 1.5 at 0.35-0.39, 2.0 at 0.25-0.34 and 2.5 at 0.15-0.24. What is her reticulocyte production index?

A 50-year-old man has hemoglobin 72 g/L (7.2 g/dL), hematocrit 0.22 L/L, RBC 2.40 × 10^12/L and reticulocytes 2.8% (reference 0.5-2.5%; absolute count reference 25-100 × 10^9/L). What best describes his red cell production?

A traveller with Plasmodium falciparum malaria (parasitemia 9%) has an automated fluorescent reticulocyte count of 6.8%. A manual new methylene blue count on the same sample is 1.4%. What most likely explains the difference?

A manual reticulocyte count uses a Miller disc, whose small square is one-ninth the area of the large square. Over successive fields, 120 red cells are counted in the small squares and 27 reticulocytes in the large squares. The reticulocyte percentage is:

After release from the bone marrow, a reticulocyte normally circulates for about how long before it becomes a mature red cell?

A 45-year-old woman has hemoglobin 82 g/L (8.2 g/dL) and a reticulocyte production index (RPI) of 1.1. The laboratory takes an RPI above 3 as an adequate response and below 2 as inadequate. This result indicates:

On a new methylene blue preparation, which finding qualifies a red cell to be counted as a reticulocyte?