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.
- Biomarkers–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.