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Platelet Disorders and Von Willebrand Disease

Key Points Platelets are highly complex cells that participate in critical steps central to hemostasis and thrombosis, including adhesion to subendothelium, aggregation, secretion of granule contents, and provision of membrane surface for activation of coagulation factors. Abnormalities of either platelet number or platelet function can play an important role in the balance of hemostasis and thrombosis. Almost unique to laboratory medicine and pathology, assessment of platelet…

Coagulation And Fibrinolysis

Key Points Physiologic hemostasis consists of endothelium, platelets, plasma coagulation proteins, natural anticoagulants, and the fibrinolytic system. Primary hemostasis involves platelets and von Willebrand factor. Secondary hemostasis is initiated by the tissue factor pathway and then amplified and propagated by the intrinsic pathway to generate thrombin that converts fibrinogen to fibrin. Routine coagulation tests (prothrombin time and activated partial thromboplastin time) may help identify a hemostatic…

Tissue Banking and Progenitor Cells

Key Points A wide range of allogeneic tissues are used for transplantation. Allograft tissue is screened, tested, and processed to improve its safety. Allograft tissue is stored by a variety of methods, including cryopreservation. Risks and complications are associated with the use of allograft tissue. A wide range of assisted reproductive techniques are available to infertile couples and individuals. Hematopoietic progenitor cells can be derived from…

Hemapheresis

Key Points Hemapheresis is the process of removing normal or abnormal components from circulating blood. Cytapheresis involves the removal of cellular components; plasmapheresis involves the removal of plasma, the liquid component. Separation of the blood components is based on size (filtration instruments), density (centrifugation instruments), or a combination of both. Donor apheresis maximizes the collection of a scarce resource by allowing donors to donate only what…

Transfusion Medicine

Key Points Criteria for blood donor eligibility are established by the U.S. Food and Drug Administration (FDA) to minimize risks to both the donor and the transfusion recipient. Blood components (red blood cells, platelet concentrates, fresh frozen plasma, cryoprecipitate) are manufactured and stored in a manner to minimize functional loss of desired constituents. Leukocyte reduction of blood components reduces alloimmunization to human leukocyte antigens, cytomegalovirus transmission,…

Immunohematology

Key Points Blood group antigens play a variety of physiologic roles as membrane structures involved in maintaining erythrocyte cytoskeleton integrity, as well as in membrane transport, cell signaling, and immune complement regulation, and as receptors/modulators of disease. The ABO histo-blood group antigens are widely expressed throughout the body and are the single most important blood group for selection and transfusion of blood products, as well as…

The Flow Cytometric Evaluation of Hematopoietic Neoplasia

Key Points Flow cytometry is a powerful, rapid, and cost-effective technique for the identification and monitoring of hematopoietic neoplasms. Successful implementation of flow cytometry requires careful attention to details of instrument and reagent performance. Normal hematopoietic cells are characterized by a reproducible gain and loss of antigen expression with maturation. Hematopoietic neoplasms show deviation from the normal patterns of antigen expression, allowing for their diagnosis and…

Leukocytic Disorders

Key Points Leukocytes are regulated by complex homeostatic mechanisms that direct their responses to infection and inflammation. Leukocytosis often reflects an underlying abnormality; leukopenia, especially neutropenia, places a patient at risk for infection. Hematopoietic neoplasms have been categorized by a World Health Organization classification according to cell of origin, cytogenetic and molecular abnormalities, immunophenotype, and clinical features. Acute leukemias are rapidly progressing neoplasms of precursor myeloid…

Erythrocytic Disorders

Key Points Anemia may result from decreased marrow production or shortened red cell survival. Nonmarrow diseases, such as endocrine, renal, and inflammatory disorders, significantly influence bone marrow function. Anemias associated with nutritional deficiencies may affect tissues other than the bone marrow. Stem cell disorders, such as inherited and acquired aplastic anemias, and paroxysmal nocturnal hemoglobinuria usually affect more than one cell line. Hemolytic anemia may be…

Hematopoiesis

Key Points Hematopoietic stem cells are a rare population of cells in the adult bone marrow that sustains hematopoiesis and gives rise to all kinds of blood cells, including granulocytes, monocytes, lymphocytes, megakaryocytes, and erythrocytes. Differentiation and maturation of hematopoietic cells are influenced by soluble factors, including growth factors and cytokines, by interaction with the bone marrow stroma, and are mediated in part through interaction of…

Basic Examination of Blood and Bone Marrow

Key Points Assessment of erythrocyte, leukocyte, and platelet counts from manual and automated particle counters is central to the diagnosis and management of hematologic disease. With few exceptions, manual methods have been replaced by automated hematology analyzers. The selection of analyzers is varied and voluminous enough to meet the needs of any hematology laboratory setting. Hematology automation combined with sophisticated algorithms for data interpretation has led…

Cerebrospinal, Synovial, Serous Body Fluids, and Alternative Specimens

Key Points Cerebrospinal fluid is an essential part of a neurologic examination, comprising special attention to cell counts, basic chemical analyses, and microbiological cultures with specific antibody titers. Determining the etiologic cause of fluid accumulation in various body cavities (synovial fluid in joints, pleural fluid in the chest, pericardial fluid around the heart, and peritoneal fluid in the abdomen) is critical for proper treatment of these…

Basic Examination of Urine

Key Points Many different diseases can display abnormalities in the urine. Therefore, examination of the urine is an important laboratory function. Basic urinalysis consists of gross examination of the urine as well as a dipstick analysis for blood, white blood cells, sugar, and other substances. The dipstick may be read manually or by an automated instrument. A microscopic analysis of urine may be necessary in many…

Chemical Basis for Analyte Assays and Common Interferences

Key Points The clinical chemistry metabolic profile gives important quantitative information for over 25 serum analytes, often facilitating diagnosis of disease. Serum electrolyte concentrations for sodium, potassium, chloride, and sometimes calcium are most commonly assayed using ion-selective electrodes. Assays for other analytes, including total protein, albumin, bilirubin, creatinine, calcium, iron and iron-binding capacity, magnesium, and phosphate, are performed using spectrophotometry on complexes that each analyte forms…

Vitamins and Trace Elements

Key Points Vitamins and trace elements are grouped because of the very small amount required to satisfy their extensive metabolic activity. Vitamins are essential organic substances that the body cannot synthesize or does not consistently synthesize sufficient for the metabolic needs. This is species specific. Vitamins may function variously as enzymatic cofactors, antioxidants, or like hormones, and are active in energy metabolism, protein metabolism, blood cell…

Reproductive Function and Pregnancy

Key Points Reproductive function and pregnancy are regulated by the complex interaction of a variety of hormones. They are synthesized and secreted by the testis (testosterone), ovary (estradiol and progesterone), pituitary (follicle-stimulating hormone [FSH] and luteinizing hormone [LH]), hypothalamus (gonadotropin-releasing hormone), and placenta (human chorionic gonadotropin [hCG], estrogens, and progesterone). Laboratory evaluation of reproductive function in the male typically begins with semen analysis. If the results…

Evaluation of Endocrine Function

Key Points The endocrine system is finely integrated—the hypothalamus, pituitary gland, and target glands continually communicate through feedback inhibition and stimulation to control all aspects of metabolism, growth, and reproduction. By understanding this interplay and carefully manipulating these systems via provocative or suppressive stimuli, it is possible to characterize an underlying abnormality and provide directed treatment. Prolactin levels can be elevated as a result of a…

Toxicology and Therapeutic Drug Monitoring

Key Points Testing for the presence of drugs in the blood and other body fluids of patients has undergone a vast increase over the past 20 years. Testing for the presence of drugs of abuse and/or poisons in patients has become mandatory both in the emergency department and in employment screening. Most drugs for which monitoring is standard can be assayed using homogeneous immunologic techniques. Gas…

Laboratory Diagnosis of Gastrointestinal and Pancreatic Disorders

Key Points Almost all patients with duodenal ulcers and most with chronic gastritis have demonstrable Helicobacter pylori infection. H. pylori stool antigen assays and urea breath tests are useful in diagnosis and in monitoring for eradication after treatment. Acute pancreatitis presents with abdominal pain and elevated levels of serum amylase or lipase. Reversible etiologies, including drug exposure, must be excluded in patients with recurrent episodes of…

Evaluation Of Liver Function

Key Points The liver is composed of three systems: the hepatocyte, concerned with metabolic reactions, macromolecular (especially protein) synthesis, and degradation and metabolism of xenobiotics (e.g., drugs); the biliary system, involved with the metabolism of bilirubin and bile salts; and the reticuloendothelial system, concerned with the immune system and the production of heme and globin metabolites (e.g., bilirubin). The function of each of these systems can…