How does infection show up in bloodwork?

Answered by Robert Dupre

Infections can often be detected through bloodwork, specifically by analyzing the levels and characteristics of white blood cells (WBCs) in the blood. When your body detects the presence of harmful bacteria, viruses, or other organisms, it triggers an immune response, which includes an increase in the production of white blood cells.

Typically, a complete blood count (CBC) is performed to assess the different types of blood cells, including white blood cells. The CBC provides information about the total number of white blood cells, as well as their distribution and specific types. The normal range for total white blood cell count varies, but it generally falls between 4,000 and 11,000 cells per microliter of blood.

An increased number of white blood cells, known as leukocytosis, is often seen in response to an infection. This occurs because your body is trying to fight off the invading pathogens. The specific type of white blood cells that are elevated can provide further clues about the nature of the infection.

Neutrophils are the most abundant type of white blood cells and are responsible for combating bacterial infections. When the body is fighting off a bacterial infection, the number of neutrophils may increase significantly, a condition known as neutrophilia. This increase is often accompanied by a left shift, which means that immature neutrophils called band cells are also present in higher numbers.

On the other hand, viral infections tend to trigger an increase in lymphocytes, another type of white blood cell. Lymphocytosis, an elevated lymphocyte count, is commonly observed in viral infections such as the flu or mononucleosis. These infections typically cause a relative decrease in the number of neutrophils.

In some cases, an increase in a different type of white blood cell, called eosinophils, may indicate an allergic reaction or a parasitic infection. Eosinophilia may also be seen in certain autoimmune diseases or in response to certain medications.

Conversely, a lower than normal white blood cell count, known as leukopenia, can indicate that your body’s ability to fight infections is compromised. This can occur as a result of viral infections, autoimmune disorders, certain medications, or bone marrow disorders. Having too few white blood cells puts you at a higher risk of developing infections, as your body’s defense mechanisms are weakened.

In addition to the total count and differential count of white blood cells, bloodwork may also include other markers of inflammation or infection, such as C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR). These markers can provide additional information about the presence and severity of an infection.

It is important to note that while bloodwork can provide valuable information, it is just one piece of the puzzle when diagnosing an infection. Other factors such as clinical symptoms, medical history, and additional laboratory tests may also be necessary to make an accurate diagnosis.

In my personal experience as a healthcare professional, I have seen numerous cases where bloodwork played a crucial role in diagnosing infections. The analysis of white blood cell counts and differentials, along with other markers of inflammation, helped guide treatment decisions and monitor the effectiveness of therapies. It is always fascinating to see how the body’s immune system responds to infections and how bloodwork can provide valuable insights into this process.