What Is Hematopathology?
Hematopathology is the study of diseases of the blood. In a broader sense, it also refers to the study of blood in diseases. This means that not only can it investigate blood diseases such as anemia or leukemia, but it can also identify non-blood diseases such as kidney disease or infection by characteristic findings the blood reveals: all illnesses affect the blood one way or another. Hematopathology, in the clinic setting, is the retrieval and testing of blood that can be evaluated microscopically and chemically to identify a wide range of conditions. Many symptom clusters are complicated, and the results of blood work allow the physician to narrow down the possibilities. This makes hematopathology an important diagnostic step. Blood is an organ unto itself, and it has many types of “tissue”:
- Red blood cells: Which contain hemoglobin, a molecule which carries oxygen to the tissues or carbon dioxide away from them.
- White blood cells: Part of the immune system, with various types and various functions.
- Platelets: part of the blood clotting cascade.
- Antibodies: another part of the immune system.
- Proteins: Fat (cholesterol/triglycerides), hormones, etc.
The list of blood components is lengthy, but there are also parts of the blood which should not be there, but which can be identified:
- Antigens: Actual infectious agents, when present, indicate what type of infection may be present.
- White blood cell shifts: In which one type of white blood cell predominates in the white blood cell population in the different types of infection (viral vs bacterial) that prompt increased production.
- Excessive electrolytes: Such as in imbalances in electrolytes (e.g., sodium, potassium, etc.) whose balance is necessary for many homeostatic processes.
- Biomarker: Chemicals whose presence indicates tissue damage–ischemia, infection, or necrosis. Examples are troponin release in myocardial infarction or myoglobin in the muscle crush syndrome (rhabdomyolysis).
Technique of Blood Retrieval
Phlebotomy: under aseptic technique, the person drawing the blood, gloved, uses newly opened disposable, sterile needles and syringes to enter a superficial vein, typically in the arm, and puts the retrieved blood into specific tubes for specific tests.
Complications From Blood Testing
Complications are rare and innocuous. Sterile technique has all but eliminated the introduction of infection via blood retrieval. Delicate vein walls can occasionally become disrupted by the puncture (“blow” or pop), leading to a temporary, self-limited collection of blood under the skin (i.e., bruising). These are not serious complications unless there is a problem with coagulation requiring prolonged pressure at the retrieval site to stop the superficial bleeding.
Diagnosis Using Hematopathology
Testing of blood is both a diagnostic test and useful for monitoring the progress or treatment of a condition, after its diagnosis, as an interval check during on-going therapy to monitor the efficacy of treatment.
Studying blood under the microscope can identify misshapen cells (e.g., sickle cells), damages cells (fragments seen from turbulence in the blood stream), and abnormal appearing cells (speckled, dark, faint, etc.) that diagnose specific disorders.
Blood as a tissue can also develop malignancy. The microscopic examination of blood may show first signs of conditions like leukemia, lymphoma, multiple myeloma, and bone cancer.
Culture of the blood can identify bacteria there, which is a prerequisite condition for sepsis, a life-threatening infection in the blood which can lead to shock. The bacteria that are grown can be tested against several antibiotics in order to drive therapeutic decisions.
The “complete blood count” is a test of the cellular parts in the blood. Red blood cells (RBC) contain hemoglobin, and a deficiency in RBC numbers is anemia. Anemia will limit the amount of oxygen carried to tissues. The red cells, in a CBC, can be categorized as to their size, volume, and hemoglobin capacity.
- White blood cells count (WBC): The “leukocyte” count is the number of immune cells that have varied functions, from releasing toxic substances to destroying invaders by engulfing them (“phagocytosis”). A rise in their numbers indicates a call to action by the immune system, i.e., infection. A decrease in their numbers implies immunocompromise or immunosuppression, often used as a warning to stop chemotherapy or seen in immunosuppressive diseases such as HIV/AIDS.
- WBC differential: In addition to a total count of the white blood cells, the leukocyte population is broken down as to type, useful in identifying an acute infection vs. a chronic one. It can also, based on the type of white blood cell that proliferates over the others, tell the difference between a viral infection and a bacterial infection or identify allergies and gastrointestinal conditions.
- Platelet count: Platelets (“thrombocytes”) are a component in the blood clotting system, and platelet count is often decreased in many illnesses, making bleeding disorders more likely.
Platelets are not the only part of the clotting cascade that is part of healing. Coagulation studies not only identify where in that complex sequence clotting can go wrong, but how affected the clotting is by medication used to slow it down, such as in thromboembolic disease.
The metabolic profile can be partial, as in a direct measurement of specific components, or complete, which can include blood glucose levels, liver function enzyme evaluation, electrolytes (sodium, potassium, calcium), kidney function elements, bilirubin that can indicate obstructive liver disease, and other tests. Hemoglobin A1c is a type of specialized diabetic test that can give a global picture (long-term average) of glycemic control.
There are different blood types that will either cooperate with transfusions or react immunologically as a life-threatening transfusion reaction. A type-and-screen will judge a patient’s blood type and Rh-factor, and a type-and-match will test it against proposed donor or recipient blood to avoid a transfusion reaction. These identify antibodies whose presence are important to recognize before any transfusion.
Certain tissue damage will release specific substances unique to that particular tissue, called biomarkers. The presence or rise of them is used to diagnose cardiac disease, muscle damage, and others. There are also biomarkers that are released my malignant cells in many cancers.
Suspicion of a specific infection (viral, bacterial, fungal, etc.) can be explored with blood tests. Tests for antibodies (made by the body) indicate exposure to a specific infectious agent; tests for antigens (the actual infectious agent) identifies on-going (current) infection and can be used via “titers” to judge the progression or remission during treatment.
Hepatitis B and C, HIV, and other viral infections can be quantitated in the body by a count of the viral load, the number of viruses in a millimeter of blood.
Pregnancy tests, thyroid function and other endocrine tests, kidney function, and diagnosis of menopause, ovarian function, and fertility conditions are easily investigated via simple blood tests.
Blood can be used to retrieve a patient’s DNA for genetic evaluation into rare, inherited disorders. The DNA can also identify mutations as a screen of those at risk for related malignancies, such as the BRCA I and II mutations in ovarian, uterine, and gastrointestinal cancer.
Management and Treatments with Hematopathology
The success of management/treatment of many illnesses can be judged by the results of interval blood tests. A good example is a blood count from a person being treated for anemia, which will demonstrate resolution of the red blood cell deficit with iron supplements.
- Viral load: A measurement of the number of viral particles in a milliliter of blood. In successful anti-HIV or hepatitis therapy, the viral load can be followed as it falls, indicating the therapy is effective.
- CD4: A type of white blood cell (T-cell), which is the immune cell damaged by HIV. A rise or a fall in the CD4 count can indicate improvement or worsening, respectively, of the disease’s effects on the body.
- White blood count: The number of white cells goes up with infection, and certain types of them will rise over the others when there are specific stimuli such as viral infection, bacterial infection, allergy, stomach conditions, etc. The certain types can be quantitated and placed in a list of counts for all of the different types, called a white blood cell count with differential.
- Immune system evaluation: Numbers of white cells can be tallied to give a picture of one’s immunological status, such as those receiving chemotherapy or radiation for cancer. This can tailor the dosing of these therapies accordingly.
- Clotting studies: Counting the number of platelets and testing to see how fast or effectively blood clots can identify a predisposition to thrombus formation, important in preventing embolic disease (clots that travel to block arteries) or in diagnosing bleeding disorders such as hemophilia. They are also useful in fine-tuning anticoagulation therapy used in clotting disorders.
- VDRL and other titers for syphilis: Although a positive VDRL only means one has had syphilis in the past, its titers (quantification) can be followed during therapy, falling as expected with successful treatment.
- Hormone levels: Thyroid function, hypofunction, or hyperfunction can be determined by thyroid stimulating hormone levels (TSH), and the fall in estrogen can be documented in therapies for endometriosis.
- Prenatal testing: Alpha-fetoprotein can give the risk of Down syndrome, as above. HCG, which rises in early pregnancy, is used as a pregnancy test, and its rising levels demonstrate that the pregnancy is progressing normally in the first trimester when there are signs of a threatened miscarriage; when not, a less-than-optimum rise can indicate a possible ectopic pregnancy.
Prevention with Hematopathology
- Blood tests are used for preventive measures: Especially in identifying those seeking immunity via vaccination/immunizations, those at genetic risk for inherited disorders, and those at high risk for diabetes, heart disease, or sexually transmitted illnesses (STIs), among many others.
- Post-immunization evaluation: After immunization, the presence of antibodies can demonstrate immunity to disease, but their absence can warn of immunization failure and disease susceptibility, important in protection from various infectious diseases for which vaccines are available. Their effectiveness can be measured.
- Glucose screening: Diabetes mellitus, both Type 1 DM and Type 2 DM, can be suspected, diagnosed, and then have its progress and management monitored with glucose levels in the blood. Once there is a diagnosis, the glycated hemoglobin A1c is a very useful test that renders an assessment of glycemic control over the previous months; it is used preventatively as a predictor for worsening disease or successful management.
- Titers: Titers are quantitative measurements of specific items that are determined by diluting blood samples until there are none of them left (by laboratory standards). The number of dilutions needed to do this quantitates an item, and its specific score—or, titer—is determined. A large amount of something will require many more dilutions than a small amount before it can no longer be counted in a sample. This is useful in determining immunity by seeing how far the dilutions go while still having antibodies after a vaccination for diseases such as measles, mumps, rubella, chicken pox, etc. Not only can it determine that there is or is not immunity there, but it can also indicate borderline immunity when the titers fall into a less than optimum range.
Titers can also quantitate disease presence. This technique can be used to estimate the antibody amount that fluctuates in accordance to disease severity. For example, in syphilis, the dilutions that show disappearance of antibodies sooner indicate ongoing eradication of disease.
- Genetic risk: Titers can also be used in assigning genetic risk with protein markers such as for prenatal risk of Down syndrome and other congenital diseases.
- Genetic studies: Useful in pregnancy and in persons who have a strong family history of inherited disorders, add an important perspective in preventative care.
- Cancer screening: There are “tumor markers” for ovarian cancer (CA-125), prostate-specific antigen (PSA, for prostate cancer), calcitonin (thyroid testing), alpha-fetoprotein (AFP, for liver cancer), HCG for testicular or ovarian cancer, and others. They are not proof, but are useful in selecting out of the general population those who should undergo more specific testing.