Understanding A Blood Test, We Explain All The Parameters To You

Red blood cells are small cells that provide oxygen to cells to carry out their functions. The oxygen is inside bound to a protein made of iron called hemoglobin.

For this reason, hemoglobin is a very useful parameter to see alterations in these cells, mainly anemias. Hemoglobin levels less than 12-13 mg / dL indicate anemia.

Anemia is a decrease in red blood cells or, rather, a decrease in their ability to carry oxygen. This can be due to different causes, to have more information about the cause of anemia there are other parameters:

• Mean corpuscular volume (MCV): measures the size of red blood cells, as it may have increased (macrocytic anemia) or decreased (microcytic anemia).

• Mean corpuscular hemoglobin (HCM): gives information about the amount of hemoglobin in each red blood cell.
• Mean corpuscular hemoglobin concentration (MCHC): relationship between hemoglobin and red cell size. It divides anemias into hyperchromic (high hemoglobin concentration) and hypochromic (the concentration is low in relation to the size of the red blood cells).
• Red blood cell distribution width (RDW): allows you to know if the size of the red blood cells is homogeneous or if there are some altered and others normal. High values ​​of this parameter suggest different types of anemia.

The opposite case, an increase in red blood cells is called polycythemia. It is marked by the number of red blood cells, which is also reflected in the analysis.

White series: white blood cells

White blood cells or leukocytes are cells that are part of the immune system. When their levels go up, it can indicate that there is an infection and they are fighting it. If the elevation is very marked, it may indicate leukemia. If, on the contrary, they decrease, it may indicate a weakness in our defenses.

There are different types of leukocytes and each one has a certain function. Therefore, in addition to the total number of white blood cells, the percentage and number of each type of leukocyte also appears. It is what is known as the leukocyte formula:

• Neutrophils: these cells are involved in the immune response against bacterial infections. If the values ​​are high, it usually indicates that there is an infection. A decrease in these is called neutropenia , and it is a major cause of immunosuppression.
• Eosinophils: they intervene in allergic reactions and parasitic infections, which is why they increase in these situations.
• Basophils: they also participate in allergic reactions.
• Lymphocytes: they are the main cells of the immune system. However, they take time to synthesize so they are more elevated in chronic infections. They are also characteristically elevated in virus infections.
• Monocytes: also elevated in chronic and viral infections.

Platelets

Platelets are blood components related to hemostasis. This process is what prevents the massive outflow of blood from the vessels when we injure ourselves, closing the affected vessel.

It also helps blood flow through the vessels, preventing clots from forming that clog them. In this sense, the main parameters are the following:

• Platelets: measures the total number of platelets in the blood. If they are elevated (thrombocytosis), the risk of obstruction of the vessels or thrombosis increases. On the contrary, a decrease in platelets (thrombopenia) makes one very susceptible to bleeding.
• MPV (Mean Platelet Volume): indicates the size of platelets, which may be increased or decreased in some diseases.

• Plaquetocrit: it is a similar value to the hematocrit but applied to platelets. In this case, the number of platelets per volume of blood is measured.

Alterations in hemostasis may be due to variation in the number of platelets or other components of this system.

If the platelet study is normal, a clotting test may be ordered, which provides more detailed information on clotting factors. These factors are molecules that participate together with platelets in the control of bleeding.

General biochemistry

This part of the blood test shows information about the metabolism of carbohydrates, lipids, and proteins. It also reflects the levels of the most abundant minerals in our body.

Hydrate, lipid and protein metabolism

In the case of carbohydrate metabolism,  blood glucose or blood glucose levels are measured. Taking into account that glucose varies depending on the time that elapses since meals, they must be within certain ranges.

If glucose levels remain elevated, it may indicate diabetes mellitus. In this disease, glucose does not enter the cells correctly, so its levels in the blood increase. In the follow-up of patients with diabetes, another parameter is also taken into account: glycosylated hemoglobin (HbAC1).

As blood sugars increase, some of it binds to hemoglobin. Normal or slightly elevated glycated hemoglobin levels indicate good disease control.

The levels of lipids or fats must be kept within a range. Although it is not good to have them low since they are part of many cellular structures and are a source of energy, an excess of them can predispose to many cardiovascular diseases.

The blood levels of the main lipids in the body are measured: triglycerides and cholesterol (HDL and LDL). When there are high levels of these parameters, they can indicate pathologies related to lipid metabolism. The best known pathology is familial hypercholesterolemia.

The routine protein study is not very extensive. The most abundant protein in blood plasma is albumin, regulating the levels of other molecules.

When the albumin concentration varies, it alters the blood pressure. It can indicate a kidney problem (where it is eliminated) or a liver (where it is synthesized). Other molecules such as uric acid, elevated in rheumatic diseases such as gout, can also be requested.

Minerals

Our body needs minerals to perform essential functions such as: muscle contraction, skeletal formation or the transmission of nerve impulses.

Variations in their levels can trigger or alter major disorders. Levels of:

• Sodium : its levels are closely related to blood volume. When its levels increase, so does the blood volume, appearing hypertension. Otherwise there is hypotension, which is usually indicative of dehydration.
• Potassium: it  is the most abundant cation within our cells. Both sodium and potassium are often altered in disorders related to the kidney, which is the organ in charge of regulating ionic levels in our body.
• Calcium:  alterations in its levels may indicate bone or parathyroid gland pathologies. There are four glands located in the neck, in relation to the thyroid gland, that regulate calcium levels.
• Chlorine: it is an ion with a negative charge that participates in the regulation of different processes. Alterations in its levels can warn of a kidney disorder.

There are many more mineral components in our body with important functions, such as iodine, phosphorus or magnesium. Its levels can be altered for multiple reasons related to specific functions or general metabolic alterations.

The main causes are kidney problems or dehydration (For example, after gastroenteritis, vomiting and diarrhea cause ionic levels to vary).

Liver profile

Another part of the blood test is the liver profile. To understand its importance, it is necessary to review the following.

The liver is an organ with a very complex function. It is involved in digestion, in the synthesis of many molecules, and in the metabolism of many waste substances. To detect possible liver disorders, the blood levels of certain enzymes that are synthesized in it are measured.

It must be taken into account that due to the complexity of this organ, many circumstances can alter their levels. Many infections and medications cause an elevation of these enzymes without meaning that the liver is diseased.

The main enzymes reflected in a blood test are the following:

• ALT and AST:  better known as transaminases. They are molecules present in many tissues related to cell metabolism.

• Alkaline phosphatase.

These molecules increase in many circumstances. A high increase in its levels is indicative of a possible liver disease, such as alcoholic, infectious hepatitis or liver cancer.

To confirm liver impairment, situations that may alter levels must be ruled out. In addition, the liver study must be completed with other tests, such as determining bilirubin.

It is a waste substance from the degradation of hemoglobin in red blood cells, it is metabolized in the liver so that an alteration in it increases its levels. A liver ultrasound may also be done.

Renal function

The kidney is the organ in charge of filtering the blood, eliminating waste substances in the form of urine. For this reason, kidney disease causes these substances to accumulate in the body, with effects that can be very harmful.

In this organ, a balance of many substances is made, such as ions and proteins. The parameters that best indicate possible kidney failure are the following:

• Glomerular filtration: calculates the amount of blood that the kidney filters per unit of time.
• Creatinine : it is a protein present in the muscles that is totally eliminated by the kidneys. If its levels increase in the blood it is indicative of kidney failure, since it is not eliminating it correctly.
• Urea : is a waste product formed in the kidney from filtered waste. Like creatinine, increased levels of urea in the blood indicate that the kidney is not filtering properly. Other tests, such as a urine test, are necessary to specify the cause and type of disorder.

Other analytical determinations

So far, the parameters that are usually requested in a general blood test have been discussed. If there is a suspicion of a specific pathology,  the doctor may decide to carry out other investigations.

For example, if a viral infection is suspected, tests may be ordered to show whether there are particles of them in the blood. This is what is called “viral serology”. Hormonal studies are also common.

Hormones are substances produced in the glands of our body to be released into the blood. Through the circulatory stream they reach the different organs, where they carry out their function. Disorders of the glands can alter their levels in the blood, which is why they are easily detectable in a blood test.