Haematology Case Studies with Blood Cell Morphology and Pathophysiology

Indu Singh, Alison Weston, Avinash Kundur, Gasim Dobie

• Éditeur: Academic Press
• Année: 2017
• ISBN:
  9780128119488
• Sujet: Medicine
• Sous-sujet: Clinical Medicine

Hematology Case Studies with Blood Cell Morphology and Pathophysiology compiles specialized case studies with specific information on various hematological disorders with Full Blood Examination (FBE or CBC), blood film images and pathophysiology of each condition. In addition, it provides basic information on how to recognize and diagnose hematological conditions that are frequently observed in the laboratory. Technicians and scientists working in core laboratories such as biochemistry labs or blood banks will find this book to be extremely thorough. Moreover, it can be used as a reference book by technicians, scientists and hematologists in every level of expertise in diagnosing hematological disorders.

• Includes morphology of red cells, white cells and platelets
• Provides images of actual blood slides under the microscope, showing the most important diagnostic features observed in each condition
• Presents details that are considered difficult for beginners or non- hematologists, such as specific tests and techniques
• Covers case studies that finish with the pathophysiology of the condition

Chapter 1

Introduction

Abstract

This chapter discusses the importance of a blood film in the diagnosis of haematological disorders and gives a brief synopsis of many haematological disorders such as microcytic anaemias, haemoglobinopathies, macrocytic anaemia, haemolytic anaemia, thrombocytopenia, thrombocytosis, leukaemia, lymphoma, and bone marrow failure. There is also a comprehensive list and explanation of terms used in this booklet.

Keywords

Provisional diagnosis; Differential diagnosis; Pathophysiology; Cytogenetics; Cytochemistry; Immunophenotyping

The Importance of the Blood Film in the Diagnosis of Haematological Disorders

Diagnostic information can be obtained from the blood smear examination if done by an experienced laboratory scientist or haematologist. Aside from the fact that it allows certain organisms to be directly visualized, peripheral blood film morphology gives helpful information on the aetiology, severity, host susceptibility, and systemic impact. It assists us to see the typical footprints left by different infections on blood cell morphology and this gives cytological clues in diagnosis such as in the case of Dohle bodies in haemophagocytosis. Physicians usually request a blood smear following perceived clinical features or irregularity of a previously done full blood count. Several factors determine whether a smear will be reviewed or not. These include the sex and age of the patient, whether such a request is an initial or subsequent one and the degree of clinical improvement from the previous result. It is possible to make a definitive diagnosis from the blood smear such as in the case of haemolytic anaemia, myelodysplastic syndrome (MDS), leukaemia, and lymphoma [1]. The morphological features of the red blood cell (RBC) and white blood cell (WBC) are important in the diagnosis of haemolytic anaemia, leukaemia, and lymphoma. The aetiology and confirmation of such diseases is then possible. Differential diagnosis can be considered which may make further investigation necessary. This booklet identifies the major roles of the blood smear in the diagnosis and differential diagnoses of anaemia, thrombocytopenia, as well as the determination and characterization of lymphoma and leukaemia. Furthermore, it highlights the further tests that should be done to confirm the diagnosis and the pathophysiology behind the condition.

Microcytic Anaemia, Haemoglobinopathies, and Blood Film Morphology

Most cases of microcytic anaemia are diagnosed by a combination of red cell indices, inflammatory markers, serum ferritin level, and clinical suspicion. However, the presence of Pappenheimer bodies and dimorphism of RBCs are helpful in the case of sideroblastic anaemia, basophilic stippling in lead poisoning, and some types of thalassemia. In the case of iron deficiency anaemia, the presence of elongated cells is the most diagnostic feature. The blood smear is also important in the diagnosis of sickle cell trait as compound heterozygosity of haemoglobin S and haemoglobin C may have a normal haemoglobin level and thus may be confused with sickle cell trait. The blood smear of a compound heterozygote usually shows irregular contracted cells, target cells, and boat-shaped cells with few classic sickle cells. So, the blood smear combined with sickle solubility test permits an accurate diagnosis [1].

Blood Film Morphology and Diagnosis of Macrocytic Anaemia

Hypersegmented neutrophils, macrocytes, as well as macroovalocytes are seen in macrocytic anaemia induced by Vitamin B12 or folic acid deficiency. In the severe form of this, one may also see red cell fragments and tear drop poikilocytes in the blood film. The blood smear is important here in that it provides provisional speedy diagnosis and allows for commencement of therapy while awaiting results. It is also useful in that it eliminates problems of false negativity of patients with remarkable B12 deficiencies that however have normal assay result. This occurs because a lot of the B12 being assayed for is bound to haptocorrin while the effective B12 bound to transcobalamin less contributes to the total B12 assay. Hepatic disease and alcohol intake usually give rise to macrocytic anaemia. In this case, the blood smear shows round (not oval) macrocytes without any hypersegmented neutrophils. However, stomatocytes and targets may occasionally be present [1]. In older individuals, macrocytosis may be caused by myelodysplastic syndromes with the blood smear often revealing hypolobulated and hypogranular neutrophils. Other morphological features include Pappenheimer bodies, blast cells, and giant platelets. Sometimes hypochromic microcytes are present which makes the smear dimorphic. In macrocytosis brought about by blood loss or recent haemolysis, RBCs usually have polychromasia due to reactionary reticulocytosis. Significant poikilocytosis is seen sometimes in macrocytic anaemia [1].

Peripheral Blood Film and Diagnosis of Haemolytic Anaemia

The shape of the RBC is important in the diagnosis of haemolytic anaemia. Certain types of haemolytic anaemia yield distinctive blood smears which can be enough for diagnosis. These include hereditary spherocytosis, hereditary pyropoikilocytosis, as well as South East Asia ovalocytosis. In hereditary elliptocytosis, the blood smear shows several elliptocytes as well as a smaller number of ovalocytes. In hereditary pyropoikilocytosis, one can see numerous poikilocytes including ovalocytes, elliptocytes, and fragmented cells. South East Asia ovalocytosis reveals poikilocytosis with macroovalocytes seen after staining specimens with May-Grunwald Giemsa stain [1]. Hyperchromic small cells are seen in conditions such as microangiopathic haemolytic anaemia burns as well as spherocytic haemolytic anaemia. The diagnosis of conditions such as disseminated cancer, haemolytic uremic syndrome (HUS), pregnancy-induced hypertension, and thrombotic thrombocytopenic purpura (TTP) is aided with the detection of a microangiopathic haemolytic anaemia. Furthermore, the blood film becomes important in diagnosing acute haemolysis brought about by oxidative damage. Morphologically, one would be able to see bite cells or keratocytes. Blister cells as well as irregularly contracted cells are also seen. Oxidative stress leading to haemolysis is seen in anaemia of G6PD deficiency. In the case of G6PD deficiency, G6PD assay can be normal as seen in acute haemolysis in G6PD-deficient individuals who usually are men of African-American origin or those females who are carriers. In these two categories, a repeat assay is indic...