Red Blood Cells (RBC) in the stool may be associated with a parasitic or bacterial infection, or an inflammatory bowel condition such as ulcerative colitis. Colorectal cancer, anal fistulas, and hemorrhoids should also be ruled out.

Red blood cells carry oxygen from the lungs to the rest of the body. They also carry carbon dioxide back to the lungs so it can be exhaled. Red blood cells (RBC) are made in the bone marrow and contain hemoglobin, a protein that carries oxygen to the tissues in the body. These cells are also known as erythrocytes.

Anemia is a condition that results from a decrease in the number of RBCs. Elevated RBC counts are seen in other conditions where there is low oxygen levels, certain drugs, kidney disease, or bone marrow overproduction. If your RBC count results are abnormal, additional tests are usually done to diagnose the cause of the high or low level of red blood cells.

A CBC measures two other components of your red blood cells:

- hemoglobin: oxygen-carrying protein

- hematocrit: percentage of red blood cells in your blood

Abnormal levels of red blood cells, hemoglobin, or hematocrit may be a sign of anemia, heart disease, or too little iron in your body.

The RBC Distribution Width (RDW) is a crucial parameter for understanding the variation in size among your red blood cells (RBCs). When a Complete Blood Count (CBC) is performed, RDW is measured to assess how much the sizes of red blood cells differ from each other in the sample. It's expressed as a percentage and provides insight into the range of sizes: a higher RDW value indicates a greater variation in size, while a lower value suggests more uniformity. Typically, red blood cells should be fairly uniform in size; deviations can indicate several types of medical conditions. For instance, a high RDW could suggest anemia caused by a deficiency in iron, vitamin B12, or folate. It can also indicate other health issues such as chronic inflammation or liver disease. RDW is often reviewed in conjunction with other CBC parameters, like the mean corpuscular volume (MCV), which measures the average size of the red blood cells. Together, these measurements help doctors diagnose the type of anemia or other underlying conditions, providing a fuller picture of a patient’s health. Understanding RDW can therefore be a vital component in diagnosing and monitoring the progress of treatment for various medical conditions.

In the analysis of cerebrospinal fluid (CSF), the presence and count of red blood cells (RBCs) is a crucial diagnostic marker, particularly when assessed as part of a cell count with differential. Normally, CSF is devoid of RBCs, as it is a clear fluid that cushions the brain and spinal cord within the central nervous system (CNS).

The RC-I / RC-IV Ratio compares the activity of Respiratory Chain Complex I (RC-I) to Respiratory Chain Complex IV (RC-IV) in buccal (cheek) cells. Because these two complexes sit at opposite ends of the mitochondrial electron transport chain, this ratio helps identify whether electron flow and energy production are balanced across the full respiratory chain.

The RC-I Activity / CS Ratio measures how well Respiratory Chain Complex I (RC-I) is functioning relative to the number of mitochondria present in cheek (buccal) cells. Complex I is the first major entry point for electrons in the mitochondrial electron transport chain and plays a key role in ATP (energy) production. This ratio helps assess mitochondrial efficiency and detect early signs of mitochondrial stress or dysfunction.

The RC-II Activity / CS Ratio measures how efficiently Respiratory Chain Complex II (RC-II) is functioning relative to mitochondrial content in buccal (cheek) cells. Complex II plays a key role in both the Krebs cycle and the mitochondrial electron transport chain. This ratio helps identify whether mitochondria are operating normally or showing signs of reduced energy-production capacity.

The RC-II+III Activity / CS Ratio measures the combined functioning of Respiratory Chain Complex II and Complex III relative to mitochondrial content in buccal (cheek) cells. Because Complex II and III work together to transfer electrons and support ATP production, this ratio helps evaluate how efficiently mitochondria are producing energy at this critical mid-point of the electron transport chain.

The RC-IV Activity / CS Ratio measures how efficiently Respiratory Chain Complex IV (RC-IV) functions in relation to the amount of mitochondria present in buccal (cheek) cells. Complex IV is a key enzyme in the mitochondrial electron transport chain, responsible for the final step of cellular energy production. This ratio helps determine whether mitochondria are performing well or showing signs of functional stress, even when the number of mitochondria (Citrate Synthase) appears normal or elevated.

The RDW value tells you whether enough of your red blood cells are of normal size and shape.

Why is this important?

The red blood cells are usually flat and lenticular (disc-shaped) with a diameter of around 7.5 µm (micrometer).

Blood cells must squeeze through the body’s smallest blood vessels, the above described capillaries, to do their job, but capillaries often become narrower than the cells in their normal disc shape. Capillaries can be as small as 4 µm in diameter. So the cells must deform and “curl up” to fit through those capillaries. Remember a normal red blood cell is around 7.5 µm in diameter.

Only when this process of “squeezing” through capillaries can happen, the supply of oxygen is guaranteed throughout the whole body.

Some red blood cells are however not optimally formed. To a certain extent this is normal as there are 2 million red blood cells formed per second. Usually there are around 85% to 89% of red blood cells developed properly.

Red Cell Distribution Width-Standard Deviation (RDW-SD) is a blood test parameter that measures the variability in the size of your red blood cells. It's one of the ways scientists assess the volume and size of red blood cells within a sample. A standard complete blood count (CBC) will often include RDW as it measures many different parts of your blood, including red blood cells. RDW can be reported in different ways, depending on the types of hematology analyzer instruments used, commonly as RDW-CV (Coefficient of Variation) or RDW-SD (Standard Deviation).

The RDW-SD specifically refers to the standard deviation of red blood cell volume, indicating how much the size of red blood cells varies around the average size. Normal RDW-SD levels are typically between 39-46 fL for adults. When the RDW-SD level is higher than normal, it may suggest that there is a significant variation in the size of red blood cells, which can be a symptom of various health conditions, such as anemia, liver disease, or other medical issues.

Red blood cells carry oxygen from the lungs to the rest of the body. They also carry carbon dioxide back to the lungs so it can be exhaled. Red blood cells (RBC) are made in the bone marrow and contain hemoglobin, a protein that carries oxygen to the tissues in the body. These cells are also known as erythrocytes.

Anemia is a condition that results from a decrease in the number of RBCs. Elevated RBC counts are seen in other conditions where there is low oxygen levels, certain drugs, kidney disease, or bone marrow overproduction. If your RBC count results are abnormal, additional tests are usually done to diagnose the cause of the high or low level of red blood cells.

A CBC measures two other components of your red blood cells:

- hemoglobin: oxygen-carrying protein

- hematocrit: percentage of red blood cells in your blood

Abnormal levels of red blood cells, hemoglobin, or hematocrit may be a sign of anemia, heart disease, or too little iron in your body.

Red blood cells can enter the urine from the vagina in menstruation or from the trauma of bladder catheterization (a procedure used to diagnose and treat cardiovascular conditions).

Rfx to HBc IgM (Reflex to Hepatitis B Core IgM Antibody)

What this test measures
The Rfx to HBc IgM test looks for IgM antibodies to the Hepatitis B core antigen, which are produced by your immune system during the early phase of a Hepatitis B infection.
“Rfx” means reflex testing — this test is automatically performed only if an initial Hepatitis B screening test (usually HBsAg) comes back abnormal or positive. It helps confirm whether an infection is recent or acute, rather than past or chronic.

Renin is an enzyme produced by the kidneys when blood volume, hydration, or salt levels are low. Its main function is to help regulate blood pressure and maintain fluid balance.

Renin activates a chain of reactions known as the renin–angiotensin–aldosterone system (RAAS). It converts a protein called angiotensinogen into angiotensin I, which is then transformed into angiotensin II. Angiotensin II constricts blood vessels, raises blood pressure, and signals the adrenal glands to release aldosterone. In turn, aldosterone prompts the kidneys to retain sodium and water, helping restore normal blood pressure and fluid levels.

If this system becomes overactive, it can lead to high blood pressure (hypertension) and may contribute to kidney or cardiovascular disease.

The reptilase clotting time measures the rate of fibrin clot formation after the addition of reptilase, a proteolytic enzyme derived from the venom of Bothrops atrox, to citrated plasma.

Reptilase is a thrombin-like enzyme. 

Unlike thrombin, which cleaves fibrinogen to produce fibrinopeptides A and B, reptilase cleaves the fibrinogen molecule to release only fibrinopeptide A.