Medical Laboratory Science Review Harr. 1.8 Hematology: Hematology Problem Solving

B. 16.7 × 109/L

B The formula for correcting the WBC count for the presence of NRBCs is:

Total WBC × 100 or (21.0 × 100) ÷ 126 = 16.7 × 109/L

where total WBC = WBCs × 109/L, 100 is the number of WBCs counted in the differential, and 126 is the sum of NRBCs plus WBCs counted in the differential.

A 19-year-old man came to the emergency department with severe joint pain, fatigue, cough, and fever. Review the following laboratory results:

WBCs 21.0 × 109/L

RBCs 3.23 × 1012/L

Hgb 9.6 g/dL

PLT 252 × 109/L

Differential: 17 band neutrophils; 75 segmented neutrophils; 5 lymphocytes;

2 monocytes; 1 eosinophil; 26 NRBCs

What is the corrected WBC count?

A. 8.1 × 109/L

B. 16.7 × 109/L

C. 21.0 × 109/L

D. 80.8 × 109/L

C. 20.0 × 109/L

C The formula for calculating manual cell counts using a hemacytometer is:

# cells counted × 10 (depth factor) × dilution factor divided by the area counted in mm2, or

(80 × 10 × 100) ÷ 4 = 20,000/μL or 20.0 × 109/L

A manual WBC count is performed. Eighty WBCs are counted in the four large corner squares of a Neubauer hemacytometer. The dilution is 1:100. What is the total WBC count?

A. 4.0 × 109/L

B. 8.0 × 109/L

C. 20.0 × 109/L

D. 200.0 × 109/L

D. 250.0 × 109/L

D Regardless of the cell or fluid type, the formula for calculating manual cell counts using a hemacytometer is:

# cells counted × 10 (depth factor) × dilution factor divided by the area counted in mm2, or

(125 × 10 × 200) ÷ 1 = 250,000/μL or 250.0 × 109/L

A manual RBC count is performed on a pleural fluid. The RBC count in the large center square of the Neubauer hemacytometer is 125, and the dilution is 1:200. What is the total RBC count?

A. 27.8 × 109/L

B. 62.5 × 109/L

C. 125.0 × 109/L

D. 250.0 × 109/L

A. A

A White blood cell identification is facilitated by analysis of the impedance, conductance, and light-scattering properties of the WBCs. The scatterplot represents the relationship between volume (x axis) and light scatter (y axis). Monocytes account for the dots in section A, neutrophils are represented in section B, eosinophils in section C, and lymphocytes are denoted in section D.

Review the scatterplot of white blood cells shown. Which section of the scatterplot denotes the number of monocytes?

A. A

B. B

C. C

D. D

C. WBC/perform manual WBC count

C When an automated WBC count is performed using a hematology analyzer, the RBCs are lysed to allow enumeration of the WBCs. Sickle cells are often resistant to lysis within the limited time frame (less than 1 minute), during which the RBCs are exposed to the lysing reagent and the WBCs are subsequently counted. As a result, the nonlysed RBCs are counted along with the WBCs, thus falsely increasing the WBC count. When an automated cell counting analyzer indicates a review flag for the WBC count, and sickle cells are noted on peripheral smear analysis, a manual WBC count must be performed. The manual method allows optimal time for sickle cell lysis and accurate enumeration of the WBCs.

Review the following automated CBC values.

WBCs = 17.5 × 109/L (flagged)

RBCs = 2.89 × 1012/L

Hgb = 8.1 g/dL

Hct = 25.2%

MCV = 86.8 fL

MCH = 28.0 pg

MCHC = 32.3%

PLT = 217 × 109/L

Many sickle cells were observed upon review of the peripheral blood smear. Based on this finding and the results provided, what automated parameter of this patient is most likely inaccurate and what follow-up test should be done to accurately assess this parameter?

A. MCV/perform reticulocyte count

B. Hct/perform manual Hct

C. WBC/perform manual WBC count

D. Hgb/perform serum:saline replacement

D. Normal values for a 2-day-old infant

D During the first week of life, an infant has an average Hct of 55 mL/dL. This value drops to a mean of 43 mL/dL by the first month of life. The mean MCV of the first week is 108 fL; after 2 months, the average MCV is 96 fL. The mean WBC count during the first week is approximately 18 × 109/L, and this drops to an average of 10.8 × 109/L after the first month. The platelet count of newborns falls within the same normal range as adults.

Review the following CBC results on a 2-day-old infant:

WBCs = 15.2 × 109/L MCV = 105 fL

RBCs = 5.30 × 1012/L MCH = 34.0 pg

Hgb = 18.5 g/dL MCHC = 33.5%

Hct = 57.9% PLT = 213 × 109/L

These results indicate:

A. Macrocytic anemia

B. Microcytic anemia

C. Liver disease

D. Normal values for a 2-day-old infant

A. Infectious mononucleosis

A Lymphocytosis with numerous atypical lymphocytes is a hallmark finding consistent with the diagnosis of infectious mononucleosis. The automated results demonstrated abnormal WBC subpopulations, specifically lymphocytosis as well as monocytosis. However, on peripheral smear examination, 60 atypical lymphocytes and only 6 monocytes were noted. Atypical lymphocytes are often misclassified by automated cell counters as monocytes. Therefore, the automated analyzer differential must not be released and the manual differential count must be relied upon for diagnostic

interpretation.

7. Review the following scatterplot, histograms, and

automated values on a 21-year-old college student.

What is the presumptive diagnosis?

A. Infectious mononucleosis

B. Monocytosis

C. Chronic lymphocytic leukemia

D. β-Thalassemia

B. Chronic myelocytic leukemia

B The +++++ on the printout indicates that the WBC count exceeds the upper linearity of the analyzer (>99.9 × 109/L). This markedly elevated WBC count,

combined with the spectrum of immature granulocytic cells seen on peripheral smear examination, indicates the diagnosis of chronic myelocytic leukemia.

8. Review the following scatterplot, histograms, and automated values on a 61-year-old woman. What is the presumptive diagnosis?

A. Leukemoid reaction

B. Chronic myelocytic leukemia

C. Acute myelocytic leukemia

D. Megaloblastic leukemia

D. None of the automated counts can be released without follow-up verification

D All of the automated results have R or review flags indicated; none can be released without verification procedures. The specimen must be diluted to bring the WBC count within the linearity range of the analyzer. When enumerating the RBC count, the analyzer does not lyse the WBCs and actually counts them in with the RBC count. As such, the RBC count is falsely elevated because of the increased number of WBCs. Therefore, after an accurate WBC count has been obtained, this value can be subtracted from the RBC count to obtain a true RBC count. For example, using the values for this patient:

Step 1: Obtain an accurate WBC count by diluting the

sample 1:10.

WBC = 41.0 × 10 (dilution) = 410 × 109/L

Step 2: Convert this value to cells per 1012 in order to subtract from the RBC count.

410 × 109/L = 0.41 × 1012/L

Step 3: Subtract the WBC count from the RBC count to get an accurate RBC count.

3.28 (original RBC) - 0.41 (true WBC) =

2.87 × 1012/L = accurate RBC

The Hct may be obtained by microhematocrit centrifugation. The true MCV may be obtained using the standard formula.

MCV = (Hct ÷ RBC) × 10

where RBC = RBC count in millions per microliter Additionally, the platelet count must be verified by smear estimate or performed manually.

9. Review the automated results from the previous question. Which parameters can be released without further follow-up verification procedures?

A. WBC and relative percentages of WBC

populations

B. RBCs and PLTs

C. Hgb and Hct

D. None of the automated counts can be released without follow-up verification

A. Redraw blood sample using a sodium citrate tube; multiply PLTs × 1.11

A The platelet clumping phenomenon is often induced in vitro by the anticoagulant EDTA. Redrawing a sample from the patient using a sodium citrate tube usually corrects this phenomenon and allows accurate platelet enumeration. The platelet count must be multiplied by 1.11 to adjust for the amount of sodium citrate. Platelet clumps cause a spurious decrease in the platelet count by automated methods. The WBC value has an R (review) flag because the platelet clumps have been falsely counted as WBCs; therefore, a manual WBC count is

indicated.

10. Refer to the following scatterplot, histograms, and automated values on a 45-year-old man. What follow-up verification procedure is indicated before releasing these results?

A. Redraw blood sample using a sodium citrate tube; multiply PLTs × 1.11

B. Dilute the WBCs 1:10; multiply × 10

C. Perform plasma blank Hgb to correct for lipemia

D. Warm specimen at 37°C for 15 minutes; rerun specimen

D. Warm the specimen at 37°C for 15 minutes; rerun the specimen

D The presence of a high titer cold agglutinin in a patient with cold autoimmune hemolytic anemia will interfere with automated cell counting. The most remarkable findings are a falsely elevated MCV, MCH, and MCHC as well as a falsely decreased RBC count. The patient's red blood cells will quickly agglutinate in vitro when exposed to ambient temperatures below body temperature. To correct this phenomenon, incubate the EDTA tube at 37°C for 15-30 minutes and then rerun the specimen.

11. Refer to the following scatterplot, histograms, and automated values on a 52-year old woman. What follow-up verification procedure is indicated before releasing these results?

A. Redraw specimen using a sodium citrate tube; multiply PLT × 1.11

B. Dilute the WBCs 1:10; multiply × 10

C. Perform plasma blank Hgb to correct for lipemia

D. Warm the specimen at 37°C for 15 minutes; rerun the specimen

C. Perform plasma blank Hgb to correct for lipemia

C The rule of thumb regarding the Hgb/Hct correlation dictates that Hgb × 3 ≈ Hct (± 3). This rule is violated in this patient; therefore, a follow-up verification procedure is indicated. Additionally, the MCHC is markedly elevated in these results, and an explanation for a falsely increased Hgb should be investigated. Lipemia can be visualized by centrifuging the EDTA tube and observing for a milky white plasma. To correct for the presence of lipemia, a plasma Hgb value (baseline Hgb) should be ascertained using the patient's plasma and subsequently subtracted from the original falsely elevated Hgb value. The following formula can be used to correct for lipemia.

Whole blood Hgb - [(Plasma Hgb)

(1- Hct/100)] = Corrected Hgb

12. Refer to the following scatterplot, histograms, and automated values on a 33-year-old woman. What follow-up verification procedure is indicated before releasing these results?

A. Perform a manual hematocrit and redraw the sample using a sodium citrate tube; multiply PLT × 1.11

B. Dilute the WBC 1:10; multiply × 10

C. Perform plasma blank Hgb to correct for lipemia

D. Warm the specimen at 37°C for 15 minutes; rerun the specimen

C. Prepare buffy coat peripheral blood smears and perform a manual differential

C The markedly decreased WBC count (0.2 × 109/L) indicates that a manual differential is necessary and very few leukocytes will be available for differential cell counting. To increase the yield and thereby facilitate counting, differential smears should be prepared using the buffy coat technique.

13. Refer to the following scatterplot, histograms, and automated values on a 48 year-old man. What follow-up verification procedure is indicated before releasing the five-part WBC differential results?

A. Dilute WBCs 1:10; multiply × 10

B. Redraw the sample using a sodium citrate tube; multiply WBC × 1.11

C. Prepare buffy coat peripheral blood smears and perform a manual differential

D. Warm specimen at 37°C for 15 minutes; rerun specimen

B. Chronic lymphocytic leukemia (CLL)

B CLL is a disease of the elderly, classically associated with an elevated WBC count and relative and absolute lymphocytosis. CLL is twice as common in men, and smudge cells (WBCs with little or no surrounding cytoplasm) are usually present in the peripheral blood smear. CLL may occur with or without anemia or thrombocytopenia. The patient's age and lack of blasts rule out acute lymphocytic leukemia. Similarly, the patient's age and the lack of atypical lymphocytes make infectious mononucleosis unlikely. Myelodysplastic syndromes may involve the erythroid, granulocytic, or megakaryocytic cell lines but not the lymphoid cells.

Review the following CBC results on a 70-year-old

man:

WBCs = 58.2 × 109/L MCV = 98 fL

RBCs = 2.68 × 1012/L MCH = 31.7 pg

Hgb = 8.5 g/dL MCHC = 32.6%

Hct = 26.5 mL/dL% PLT = 132 × 109/L

Differential: 96 lymphocytes; 2 band neutrophils; 2 segmented neutrophils; 25 smudge cells/100 WBCs

What is the most likely diagnosis based on these

values?

A. Acute lymphocytic leukemia

B. Chronic lymphocytic leukemia (CLL)

C. Infectious mononucleosis

D. Myelodysplastic syndrome

B. Hereditary elliptocytosis (ovalocytosis)

B The finding of ovalocytes as the predominant RBC morphology in peripheral blood is consistent with the diagnosis of hereditary elliptocytosis (HE), or ovalocytosis. This disorder is relatively common and can range in severity from an asymptomatic carrier to homozygous HE with severe hemolysis. The most common clinical subtype is associated with no or minimal hemolysis. Therefore, HE is usually associated with a normal RBC histogram and cell indices and will go unnoticed without microscopic evaluation of the peripheral smear.

15. Refer to the following scatterplot, histograms, and automated values on a 28-year old woman who had preoperative laboratory testing. A manual WBC differential was requested by her physician. The WBC differential was not significantly differentfrom the automated five-part differential; however, the technologist noted 3+ elliptocytes/ovalocytes while reviewing the RBC morphology. What is the most likely diagnosis for this patient?

A. Disseminated intravascular coagulation (DIC)

B. Hereditary elliptocytosis (ovalocytosis)

C. Cirrhosis

D. Hgb C disease

A. Osmotic fragility

A The osmotic fragility test is indicated as a confirmatory test for the presence of numerous spherocytes, and individuals with hereditary spherocytosis (HS) have an increased osmotic fragility. The MCHC is elevated in more than 50% of patients with spherocytosis, and this parameter can be used as a clue to the presence of HS. Spherocytes have a decreased surface-to-volume ratio, probably resulting from mild cellular dehydration.

A 25-year-old woman saw her physician with symptoms of jaundice, acute cholecystitis, and an enlarged spleen. On investigation, numerous gallstones were discovered. Review the following

CBC results:

WBCs = 11.1 × 109/L MCV = 100 fL

RBCs = 3.33 × 1012/L MCH = 34.5 pg

Hgb = 11.5 g/dL MCHC = 37.5%

Hct = 31.6 mL/dL PLT = 448 × 109/L

WBC differential: 13 band neutrophils; 65 segmented neutrophils; 15 lymphocytes; 6 monocytes; 1 eosinophil RBC morphology: 3+ spherocytes, 1+ polychromasia

What follow-up laboratory test would provide valuable information for this patient?

A. Osmotic fragility

B. Hgb electrophoresis

C. G6PD assay

D. Methemoglobin reduction test

D. β-Thalassemia minor

D β-Thalassemia minor can easily be detected by noting an abnormally elevated RBC count, an Hct that does not correlate with the elevated RBC count, in conjunction with a decreased MCV. Although thalassemia and IDA are both microcytic, hypochromic processes, thalassemia can be differentiated from IDA because in IDA the RBC count, Hgb, and Hct values are usually decreased along with the MCV. Although the RBC count is increased in PV, the Hct must also be higher than 50% to consider a diagnosis of PV.

17. Refer to the following scatterplot, histograms, and automated values on a 53 year-old man who had preoperative laboratory testing. What is the most likely diagnosis for this patient?

A. Iron deficiency anemia (IDA)

B. Polycythemia vera (PV)

C. Sideroblastic anemia

D. β-Thalassemia minor

B. Hgb electrophoresis

B The findings of a moderate anemia, numerous target cells seen on a peripheral blood smear, as well as the presence of NRBCs, are often associated with hemoglobinopathies. Hemoglobin electrophoresis at alkaline pH is a commonly performed test to correctly diagnose the type of hemoglobinopathy.

Review the following CBC results:

WBCs = 11.0 × 109/L MCV = 85.0 fL

RBCs = 3.52 × 1012/L MCH = 28.4 pg

Hgb = 10.0 g/dL MCHC = 33.4%

Hct = 29.9 mL/dL PLT = 155 × 109/L

12 NRBCs/100 WBCs

RBC morphology: Moderate polychromasia, 3+ target cells, few schistocytes

Which of the following additional laboratory tests would yield informative diagnostic information for this patient?

A. Osmotic fragility

B. Hgb electrophoresis

C. Sugar water test

D. Bone marrow examination